Warning

 

Close

Confirm Action

Are you sure you wish to do this?

Confirm Cancel
Member Login

Site Notices
Arrow Left Previous Page
Page / 2
Posted: 8/11/2017 2:33:20 PM EST
[Last Edit: 8/11/2017 5:38:12 PM EST by dyeager535]
Gas gun, 16"bbl, , bullets anywhere from 130-190grs (edit, 125-190)

Normally have loaded 2.83" OAL for all. Mil brass, full length resized.

I always start with minimum loads, assuming load data is given.

Started noticing that many of the "minimums" are resulted in primers that are beyond flattened. Primer cups are creating flakes you can pick at with your fingernail. If you google flattened primer, you'll find some like I'm getting. These are mild compared to what I'm seeing: Find a pic of a primer where the primer pocket and primer merge, and that's it.

Again, these are near or at minimum loads (more edit...maybe more in the midrange). I don't have my load data handy, but my question is more about the effect of OAL.

From everything I've read (and common sense I suppose) longer OAL generally seen as likely to reduce pressure. But is there a circumstance where increasing OAL (+.03") is likely to result in more pressure?

It may be negligence, but I generally never paid attention to the OAL listed in the books. I loaded less than into the lands, and play around from there. I'm no benchrester obviously. But it's not caused issue before.

The issue I am trying to wrap my head around, is that I'm seeing this with what I'm believing are light loads (scale weights verified) from 130-190gr bullets, so the profile is going to be different. It doesn't seem logical 3+ different bullet weights all have problems at the same 2.83" OAL.

I'm going to re-verify my FPS results vs. charge weight and barrel length, but from cursory looks, something isn't right to be at so much pressure as soon as I am. I'm recalling this is even occurring at ~2200FPS with 190's. Which may be accurate with the barrel difference from 24" test rigs to a 16"?
Link Posted: 8/11/2017 3:42:52 PM EST
No ballistics scientist here, but you're generally right about longer COAL resulting in less pressure. I'm sure there are exceptions with the odd super long bullet and how it might extend into the case body, but your 2.83 for .308 Winchester by itself shouldn't generally be an issue, especially at the lower powder charges you mention.

I see COAL's for 130g bullets being at the 2.690" and generally going to 2.80" as you get to 150g and higher.

What gun is this? I have a pair of Armalite .308's with properly sized firing pins and appropriate aperture size for the pin. Some other brands are know for having poor bolt face, firing pin, and aperture size which can result in some funky primer issues. Just throwing that out there.

I'm guessing you haven't chrono'd these rounds for a comparison.
Link Posted: 8/11/2017 4:38:18 PM EST
Can we get some idea of your loads? Bullet, powder used and grains, brass manufacturer, and primer?
Link Posted: 8/11/2017 4:44:30 PM EST
As the last post stated 2.800" is usually maximum length for a .308 Win but it's totally depends on your specific chamber.

A longer AOL does typically mean lower pressure but there is a limit because as AOL gets longer bullet jump decreases. At what point does the decreased jump start to make pressure rise (less momentum entering the lands) I don't know but I do know the ZERO jump definitely increases pressure.

Another thing I want to mention is that light loads often result in false primer reading. The reason is that light loads often don't drive the casing back against the bolt face allowing the primer to back out of the pocket and expand.

Then as the pressure get high enough to break the hold the casing has on the chamber wall it moves back crushing the primer resulting in a primer that "looks" like it was used with a top end load.

Motor
Link Posted: 8/11/2017 5:23:05 PM EST
I'm sorry I'm not sitting at my PC with load data on it. It's a GII, but I don't know why a different semi-auto gun would be much different than as you'd see in mass production tolerances. I've got an adjustable gas block on it, and it's turned down as far as it will go and still cycle.

The data I'm using is from here:
Barnes 308
Nosler 308

If I have to throw out a number, I believe 41.5grs of Varget against a 190gr ABLR is in the mangled primer realm. I've got the real numbers at home, I can post them, along with FPS I got from the ones I measured.

One case the extractor ripped the rim off, others that were indicating high pressure also show extreme deformation of the extractor groove. Loads that primers indicate pressure to be acceptable do not mangle the rim. I don't know as ejector marks are normally an indicator, but there doesn't seem to be anything abnormal in regards to the ejectors marking the case head. If they are, it's the customary slight dimple.

I may be expecting too much from a 16" barrel, but using the roughly 25FPS per inch loss as a rough estimate I don't think I'm where I should be FPS-wise, while still within safe pressure limits.

Oddly, as I recall, the Barnes 130's I've been shooting allow near or maximum loads at the 2.83" OAL, while GMX 125's show extreme pressure signs with similar loads. There is no 125gr GMX load data, so I was trying to work those up.
Link Posted: 8/11/2017 8:08:28 PM EST
Sounds like loose headspace.
Link Posted: 8/11/2017 8:29:52 PM EST
Brass selection is key when using load data. All military surplus foreign and domestic 7.62x51mm brass is too heavy to use standard published loads. Common case weights for this type of brass is 180 grains +/- empty and unprimed.

Many published starting loads are maximum powder charges when loaded in military surplus cases.

The NRA published several articles in the 1980's and compiled them in a book titled: "Semi-Auto Rifles - Data & Comment". While this book has been out-of-print for twenty years now, it is still available online from used book stores. It is the single best load data source I have ever reference when using Lake City 7.62x51mm brass. Close to 1000 rounds were pressure test fired through a Universal Receiver and accuracy, charge weights and pressures were meticulously recorded for our referencing pleasure. The work was done by none other than ballisticians William C. Davis Jr. and assisted by E.C. Harris. Wm. C. Davis Jr. was the USA representative to NATO for ammunition compatibility and personally responsible for developing the load data for M80 ball and other US Military 7.62x51mm ammo.

Maximum loads are at least 2.0 full grains lower when using G.I. brass, sometimes more. More people have trouble with this nowadays it seems IMO for several reasons:

1. 7.62mm brass is no longer sold directly to CMP (formerly DCM) affiliated gun clubs by the United States Army. This practice ended over twenty years ago and because there isn't a steady stream of it, people are mostly on their own when developing loads.

2. 7.62mm rifles have all but disappeared from NRA tournaments. What used to be THE gun to shoot and when everyone shared load data has gone the way of the dinosaur. Without a large support and mentoring society, the widely known facts regarding the use of this brass and the reduced charge weights required evaporates from conversation.

I posted the articles in an old thread at this site which is still available. I will try to locate it and bump it to the top for the OP.
Link Posted: 8/11/2017 8:33:33 PM EST
I'm sorry, but Photobucket has seen fit to disable my posted pictures. The thread is now useless without the download.
Link Posted: 8/12/2017 12:26:33 AM EST
[Last Edit: 8/12/2017 2:24:11 AM EST by dyeager535]
I actually have a copy of that article kicking around somewhere.

For load development I had actually segregated my brass (all LC 12 that I'm shooting now) into weight ranges, and what I got from that outside of a few outliers has a variation of only 1% in case weight. But what I shoot has even less case weight variation since I was segregating by weight and didn't know how the weight range would turn out on the batch I was doing. That probably isn't the greatest way to determine the case capacity, but it has to be close given the same external dimensions.

My understanding regarding brass volume though, is that it's somewhat of a linear relationship...less case capacity requires less powder to achieve the same pressure and velocity, and more case capacity requires more powder to achieve the same velocity. Off the top of my head commercial brass is somewhere on the order of 12% lighter, and that would be a significant change. But overall, that would seem to indicate similar velocity with more or less case capacity should be possible.

Looking at some of my load data, 42.7grs of Varget with the 168SMK yields a velocity of 2410FPS and case head separations, and the 190 ABLR's at 41.6grs of Varget are going 2291FPS and showing signs of impending failure. I'd consider all this brass scrap, as the extractor has deformed the case head, and another extractor pull on the same spot would very likely rip through.

Realistically it looks like where the loads are starting to show real pressure problems is within 10% or less of published maximum with civilian brass, which is pretty close to the percent weight difference in civ vs. mil brass weight.

I'm really not interested in pushing the bullets fast just for the sake of doing so. I need a few loads that can push the bullets fast so they will still expand for hunting with as much range as is possible, and there speed is a more significant factor than accuracy is, as long as the tradeoff is not very large. If need be, I could use civ brass for those, and consider the brass disposable. I just happened to notice that when determining maximum, the pressure signs seemed to come on fairly strong earlier than I expected, and it made me curious, since reduction in pressure is covered quite clearly, then I noticed that the manufacturers with some bullets were running significantly shorter loadings. For instance the Barnes 130 TTSX, which are a full .1" shorter OAL than what I have been loading.

Interesting note on the Barnes, I can get pretty close to book max before pressure signs get bad, but the velocity variation just below maximum is pretty terrible (+/-150FPS), where at the book max I saw a 20FPS difference.

I plan to make sure the various loads at 2.83" aren't closer to the lands than I expect they are, and I'll shorten them a bit at a time and see if that changes where I start to see pressure signs. I've got a couple of other powders to try as well. If nothing else, it's interesting to see all the interrelated factors.
Link Posted: 8/12/2017 12:57:16 AM EST
How much are you bumping the shoulder?
Link Posted: 8/12/2017 2:17:42 AM EST
These have all been resized/trimmed/swaged by a commercial company.

Other than putting a slight chamfer on the case mouth, I don't do any prep work on them.

I have some "virgin" (demil) brass that I could compare with, but I noticed a few grains of powder remain in most of them, apparently glued in with the bullet sealant, so I figured they wouldn't be good ones to use for trying to find max loads, even if it's a minuscule amount of extra powder.
Link Posted: 8/13/2017 3:52:49 PM EST
While velocity may seem needed, your 16" barrel loses at least 200 fps compared to identical loads fired from a 24". Nothing can be done to change that. Consider using lighter bullets.

Your powder charges of 42.7 grains of Varget is probably too hot by .7 to 1.0 grain. 42.0 grains of VihtaVuori N150 is an absolute maximum in my rifles. N150 is slower than Varget. I have settled on 41.5 grains of N150 as a working load using 168 SMK's in Late City brass.

I would try 40.0, 40.5, 41.0 and 41.5 grains of Varget with the 168's looking for accuracy period. You are only going to safely reach 2350 to 2400 fps before pressure is over the top.
Link Posted: 8/13/2017 6:08:31 PM EST
I've considered switching to 168's, but I've got to run the numbers on those to see if they would get me any further out than running the 190's in the safe (but exceedingly slow) range, since I already have a handful of them. My suspicion is that what the lighter bullets gain from velocity, they will lose over distance compared to the better BC 190's. I could be wrong, but I fully realize there is no free lunch. I've considered running the 190's and loading the rifle individually, but kind of defeats the purpose of a semi-auto. I did check, and 2.9" OAL with the ABLR's is not an issue.

Was just hoping that the ~200FPS loss from barrel length wasn't the sole factor and I might be able to gain some velocity while shaving pressure by refining technique and components. Since I already have some of the 190's loaded up that are on the hot end, I may try working up a single shot load with the longer OAL, just to see what the relationship is between case capacity, pressure, and velocity. I'm not expecting magic, and that the velocity stays the same but pressure goes down, but it will be interesting to quantify.

41.5grs with 168's is right on the cusp of pressure limits it appears from my previous load data, 41.4" was still indicating as "safe", but as you mentioned, it's going to be in the mid 2300's at best.
Link Posted: 8/13/2017 9:00:34 PM EST
Originally Posted By dyeager535:
Started noticing that many of the "minimums" are resulted in primers that are beyond flattened.
View Quote

I think this is the issue. Primers often push themselves back out of the pocket, and usually the pressure of the gas pushes the case back against the bolt face, re-seating the primers. Your minimum loads might not be hot enough to reseat the primers, which flattens them...

Going only by "reading primers" is a poor way to monitor load pressure. How do these rounds perform? How's the accuracy? How is the recoil?
Link Posted: 8/14/2017 12:17:14 AM EST
I re-clarified my "minimum" statement, my issues are more "mid" range.

I shoot subs as well, and the primers back out of those. I can't imagine a primer flattening like this with that sort of pressure.

Ripping the rims off is probably another pretty good indicator of pressure I think, along with case head separations, both of which I've had.
Link Posted: 8/14/2017 12:32:45 AM EST
Ripping rims off and some of the other issues you mentioned are also signs of an over gassed system. Basically trying to extract the casing while pressure is still holding it tightly against the chamber wall.

Motor
Link Posted: 8/14/2017 1:03:14 AM EST
I could go back and try to adjust the gas down a bit, but if I can get any more adjustment out of it, it's going to be one click. It's turned way down already. Pain to deal with adjusting gas when you fire two rounds then change to another load, over and over again. Which is one reason why I was hoping to get two loads figured out, so I could set the gas and forget it.

Ripped rims, case head separations, and flattened primers, together, to me indicate pressure is the issue, too much gas is going to be a symptom of that IMO.
Link Posted: 8/14/2017 2:21:27 AM EST
I wouldn't include case head separation in there. The only reason you should have head separation is worn out brass. Shooting hot loads "should" have only a minor impact on brass ware.

Unless you are over gassed and the casings are expanding more than they should because the bolt is opening too soon.

Don't get wrong. I think you're approach is correct. You'll get it sorted out.

Motor
Link Posted: 8/14/2017 7:52:14 AM EST
Link Posted: 8/14/2017 12:25:32 PM EST
[Last Edit: 8/14/2017 3:05:27 PM EST by dyeager535]
Thanks for that link! Interesting stuff, I love numbers, have to take time to digest it all. Significant change in pressure as length increases, unfortunately I can't go any further than 2.83".

FWIW, the brass is once fired. Obviously machine gun brass, but not showing any signs of separation when initially loaded. As loads get hotter, you can see the ring where separation will occur get brighter and brighter, for lack of a better way to describe it. The section that will separate is clearly obvious. Not mine, but this is pretty much the same:

Link Posted: 8/14/2017 1:29:36 PM EST
I just pulled some cases out of my scrap bin. The black marks are where the sizing die stops sizing. The red marks are where the case is separating on the inside found with the 'paper clip' test, actually a dental pick, and marked on the outside. When I look at your picture, all I'm seeing is where the sizer stopped.

Link Posted: 8/14/2017 1:36:38 PM EST
Still sounds like loose headspace, and over gassed.
Link Posted: 8/14/2017 1:50:55 PM EST
I just happened to have these 308 sectioned cases over on the bench. They may give you a better idea of how far up the separation occurs.

I don't know if where it separates could be in different spots on a 308 or not - but I'd say it could given my red marks on the cases above. But I do know when I was having issues with 556 cases, the separation was much closer to the shoulder vs the head. I've always heard it starts where the case walls thin down from the web.
Link Posted: 8/14/2017 2:02:00 PM EST
Originally Posted By dyeager535:
Gas gun, 16"bbl, , bullets anywhere from 130-190grs (edit, 125-190)

Normally have loaded 2.83" OAL for all. Mil brass, full length resized.

I always start with minimum loads, assuming load data is given.

Started noticing that many of the "minimums" are resulted in primers that are beyond flattened. Primer cups are creating flakes you can pick at with your fingernail. If you google flattened primer, you'll find some like I'm getting. These are mild compared to what I'm seeing: https://americanhandgunner.com/wp-content/uploads/2016/08/BETTER-2b.jpg Find a pic of a primer where the primer pocket and primer merge, and that's it.

Again, these are near or at minimum loads (more edit...maybe more in the midrange). I don't have my load data handy, but my question is more about the effect of OAL.

From everything I've read (and common sense I suppose) longer OAL generally seen as likely to reduce pressure. But is there a circumstance where increasing OAL (+.03") is likely to result in more pressure?

It may be negligence, but I generally never paid attention to the OAL listed in the books. I loaded less than into the lands, and play around from there. I'm no benchrester obviously. But it's not caused issue before.

The issue I am trying to wrap my head around, is that I'm seeing this with what I'm believing are light loads (scale weights verified) from 130-190gr bullets, so the profile is going to be different. It doesn't seem logical 3+ different bullet weights all have problems at the same 2.83" OAL.

I'm going to re-verify my FPS results vs. charge weight and barrel length, but from cursory looks, something isn't right to be at so much pressure as soon as I am. I'm recalling this is even occurring at ~2200FPS with 190's. Which may be accurate with the barrel difference from 24" test rigs to a 16"?
View Quote


Do these loads do the same thing in other rifles? Your 2.830 COAL may be a bit long...and if you're jamming that bullet into the lands you could be seeing a pressure spike. You may hae a headspace issue with that particular rifle. Get a hornady headspace gauge, case, and a comparator. Check what seating depth (off the ogive not the meplat) you're hitting the lands for each projectile. Make sure your don't have a short chambered rifle.
Link Posted: 8/14/2017 2:04:55 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By TripletDad:
I just happened to have these 308 sectioned cases over on the bench. They may give you a better idea of how far up the separation occurs.
https://www.dropbox.com/s/522a2nls0ususti/IMG_0903.JPG?dl=1
I don't know if where it separates could be in different spots on a 308 or not - but I'd say it could given my red marks on the cases above. But I do know when I was having issues with 556 cases, the separation was much closer to the shoulder vs the head. I've always heard it starts where the case walls thin down from the web.
View Quote
7.62 NATO brass (specifically the TAA and LC I use) will thin out at the web. Doing a little experiment (used a bolt gun) I got 8 loadings beofre I experienced two partial separations. Pulled the bullets and powder and tossed the brass. I go with 6 loadings and then toss the brass now. This is full length sizing and trimming after each firing. The brass is cheap...so 6 is a good number for me. My loads are also fairly warm.
Link Posted: 8/14/2017 2:11:45 PM EST
Both the sectioned cases I posted are LC.

I just didn't want the OP tossing good brass if he thought the ring that I'm seeing on his picture is what he was taking as the brass stretching. I think it's just where the sizer stops.

My standard case prep is to run a dental pick inside each case after all the sizing, trimming, cleaning is done. If I feel a rough spot, I'll draw a red line around it and scrap it after the next firing. If the pick catches, I toss it right then.
Link Posted: 8/14/2017 2:24:28 PM EST
[Last Edit: 8/14/2017 2:25:30 PM EST by cms81586]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By TripletDad:
Both the sectioned cases I posted are LC.

I just didn't want the OP tossing good brass if he thought the ring that I'm seeing on his picture is what he was taking as the brass stretching. I think it's just where the sizer stops.

My standard case prep is to run a dental pick inside each case after all the sizing, trimming, cleaning is done. If I feel a rough spot, I'll draw a red line around it and scrap it after the next firing. If the pick catches, I toss it right then.
View Quote
Gotcha. I can't see the pictures on the computer here at work. That's a good SOP once you hit 4-5 firings...even if it's just to spot check one in 10 cases. I've loaded standard (not LR) LC brass exclusively for the last 10 years. Folks fork out big money for Lapua brass and the like...but with FL sizing, culling for off center primer pocket holes, swaging the crimp, trimming, and then treating it like normal brass, I've had excellent results. I don't turn necks nor do I anneal. Too much time involved and I have to try pretty hard to get any load/powder charge to not shoot at least MOA with my current process. Small dings from MG ejection don't hurt anything and the only change in SOP from sizing normal brass is running the primer pin on the sizing die out a bit further to fully punch out the crimped primer....but you probably know all of this already if you're shooting LC brass too.
Link Posted: 8/14/2017 2:59:52 PM EST
[Last Edit: 8/14/2017 3:19:02 PM EST by jjman15]
Lots of posts here but quickly sifting i'm not seeing what came to my mind. Primer flow, which is normal, by design, under most circumstances with 308 AR dpms bolts. I was in a similar scenario when working up a hot load last year, I was seeing what I thought was overpressure signs on the primer at minimum loads.

The cause is the correlation between the hole in the bolt face and the diameter of the firing pin. On a "standard" dpms bolt when the firing pin is protruded their is a decent gap or ring between the firing pin edge and the ID of the hole that it passes through. The primer "flows" into that gap and leaves you with a crater that you immediately think is overpressure. Some primers do it worse than others depending on how thick the cups are.

JP does make a bolt that addresses this if it bothers you, I believe it's called the "high pressure" bolt group and comes with a new pin. The pin and pin hole are tighter tolerances so the primer has no where to flow.

Long story short, you should be OK but the only way to know is with a chronograph and knowing what your max velocity is before you reach max pressure. If you really are seeing "flattened" primers as in completely flat around the edge you may be overpressure. If your using lake city brass generally it has a few grains less case capacity which means less volume which means you'll reach higher pressures quicker. You need to chronograph these.

EDIT: just read your post about the rims getting ripped off, that's an issue. You need to have someone run a quickload for you to find out what your max velocity is for the 16" barrel.
Link Posted: 8/14/2017 3:33:34 PM EST
[Last Edit: 8/14/2017 3:35:02 PM EST by dyeager535]
So that previous picture probably wasn't good as an example. Updated, but here is another one:



I have not sectioned a case, but it is exactly where my separations have occurred, so it is unquestionably what I'm seeing. They, just like the primers, get much more distinct as the loads increase in powder charge. Again, these are all once fired cases that have no visible signs of separation when I load them.

Unfortunately I don't have, nor do I know anyone that has a .308 I could check the loads in. I verified that my loads are nowhere near the lands, but the previous link indicates that even if it were, pressure rise from being against the lands is much less than the pressure lost from increasing OAL. At the closest I'm .070" off the lands. I don't have the comparator and all that, but the bolt easily closed at 2.9" OAL, and my loads are 2.83" OAL, so I stopped lengthening them when I saw it was at least that far off the lands.

Let me see if this link works. This is much closer to what I'm seeing on even my upper-mid level loadings in terms of primer. There is a bit of cratering, the GII does have a fairly good sized firing pin tunnel, but that is not what is leading to the primer material merging with the brass. On some of mine it's actually forcing primer material out of the primer pocket at the edges, which can be picked off with your fingernail.



Here is what the rims start to look like as the loads get hotter:



I apologize for not having a camera good enough to take images that are what I am actually seeing, but the ring on the brass, primer depicted, and extractor damage are definitely what I am experiencing.

Obviously I'm not breaking new ground here as evidenced by all the linked photos of the same things I'm seeing.
Link Posted: 8/14/2017 3:50:18 PM EST
[Last Edit: 8/14/2017 3:54:10 PM EST by jjman15]
Your OAL is restricted by mag length so distance to lands isn't really relevant here.

You really can't go anywhere from here without a chronograph and knowing how fast those loads are going. As mentioned above if your running book measurements in a lake city case it's possible your way over pressure. For example on one of my recent loads, also for a 16" gas gun, I had to go up 2.9 grains on my charge weight when switching from lake city brass to hornady brass in order to get the same velocity.

What is your end state here, what are you trying to achieve? Your only gripe at this point is your seeing overpressure at min loads but that doesn't mean that your not achieving the velocity of the max load in a 16" barrel. Most of those book loads are based on a 24" barrel so you need to cut off at least 2-300 feet per second on your expectations on the 16". The 25 fps per inch that you mentioned earlier is complete BS, their's no way of knowing exactly without doing the testing on your setup.
Link Posted: 8/14/2017 3:53:31 PM EST
Do you have headspace gauges? I'd start there at this point or send your rifle back to DPMS. That's obviously not normal, and if you're sure your loads are GTG...and your rifle does this with factory ammo...then they will fix it.
Link Posted: 8/14/2017 4:14:36 PM EST
[Last Edit: 8/14/2017 4:17:39 PM EST by dyeager535]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By jjman15:
What is your end state here, what are you trying to achieve? Your only gripe at this point is your seeing overpressure at min loads but that doesn't mean that your not achieving the velocity of the max load in a 16" barrel. Most of those book loads are based on a 24" barrel so you need to cut off at least 2-300 feet per second on your expectations on the 16". The 25 fps per inch that you mentioned earlier is complete BS, their's no way of knowing exactly without doing the testing on your setup.
View Quote
I'm trying to get the ABLR's to stay above 1300FPS for as far as possible, and it wouldn't hurt to keep the TTSX's going as fast as possible either, since the expansion threshold is fairly high (1800FPS).

If 2-300FPS less is what my expectation should be, then ~25FPS is nowhere near complete BS (25FPS x 8" = 200FPS). I am fully aware 100FPS is within what all the variables could result in from one gun to the other.

"Looking at some of my load data, 42.7grs of Varget with the 168SMK yields a velocity of 2410FPS and case head separations, and the 190 ABLR's at 41.6grs of Varget are going 2291FPS"

Those FPS, at least for the 190's, are right where you'd be with 2-300FPS loss for 8" less barrel length from Nosler's load data (2572FPS max with Varget out of a 24" barrel) and those are what I consider unsafe loads, so it's probable I'd be significantly slower backing the powder charge down to where I am not seeing pressure signs.

The gun was in for warranty work for some unrelated issues (receiver extension), I would hope that the gun was tested both when produced, and when in for warranty work, but I can't guarantee that. I've not run factory ammo in the gun. No head space gauges.

The problems do go away when charge weight is reduced. I'm not sure that indicates a headspace issue.
Link Posted: 8/14/2017 5:07:10 PM EST
Yes, this is a much clearer picture to me. I thought you were talking about the rings that I have marked with the green arrow in your replacement picture. I believe those are where the sizing die stopped.

The ring between the red arrow and the end of the punch's shadow is a stretch mark.

If you can measure the water capacity of one of the fired cases and give me the exact load recipe (COAL, bullet manufacturer and part number, powder, charge weight,) I'll be happy to run it through QuickLOAD and give you its pressure prediction and velocity for a 16" barrel. Just remember, it's only a prediction though.
Link Posted: 8/14/2017 6:05:51 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By TripletDad:
Yes, this is a much clearer picture to me. I thought you were talking about the rings that I have marked with the green arrow in your replacement picture. I believe those are where the sizing die stopped.
https://www.dropbox.com/s/pfj2obuegivd10e/casehead02_edited1.jpg?dl=1
The ring between the red arrow and the end of the punch's shadow is a stretch mark.

If you can measure the water capacity of one of the fired cases and give me the exact load recipe (COAL, bullet manufacturer and part number, powder, charge weight,) I'll be happy to run it through QuickLOAD and give you its pressure prediction and velocity for a 16" barrel. Just remember, it's only a prediction though.
View Quote
I'll go a step further trying to help and will load up the same load data if you post it up and see how it looks.
Link Posted: 8/14/2017 7:12:24 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By HighpowerRifleBrony:
Still sounds like loose headspace, and over gassed.
View Quote
I can't help feeling the same. One other scenario is that the brass was fired in a really loose machine gun which stretched it excessively.

Twice sized brass should never look that close to failure (particularly that type of failure, head separation) there is something wrong here and it's not from being a little hot on the load data.

Motor
Link Posted: 8/14/2017 7:19:32 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By dyeager535:

The problems do go away when charge weight is reduced. I'm not sure that indicates a headspace issue.
View Quote
Bingo! Lower your powder charge and look for accuracy instead.
Link Posted: 8/14/2017 11:56:45 PM EST
I'm short on time to measure my SPECIFIC cases unfortunately, but have found various sources online that show same case capacity for LC cases of the same weight I'm using, one year difference (LC12 is what I'm using, data from LC13). Even within the same year the capacity measured varies quite a bit (+/- 5.6grs), but I took the least volume to work with that appears fairly consistently. If I'm going to take a guess (for now at least) on case capacity, it needs to be worst case scenario.

54grs of water capacity for all (same headstamp/cartridge weight within .5 grs), LC12.

FED210 primers
41.6grs Varget
Nosler Accubond Long Range 190gr Part number 58456
2.83" OAL
2291FPS average

FED210 primers
42.7grs Varget
Sierra Match King (open tip) 168gr Stock Code 2200 (qty 100, plain, not moly)
2.83" OAL
2410FPS average

FED210 primers
49.1grs Varget
Barnes 130gr TTSX SKU: 30364
2.83" OAL
2906FPS average

FED210 primers
52grs CFE223
Hornady 125GMX Item number: 30190
2.83" OAL
2862FPS average

All four of those exhibit overpressure signs.
Link Posted: 8/15/2017 12:16:31 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By dyeager535:
I'm short on time to measure my SPECIFIC cases unfortunately, but have found various sources online that show same case capacity for LC cases of the same weight I'm using, one year difference (LC12 is what I'm using, data from LC13). Even within the same year the capacity measured varies quite a bit (+/- 5.6grs), but I took the least volume to work with that appears fairly consistently. If I'm going to take a guess (for now at least) on case capacity, it needs to be worst case scenario.

54grs of water capacity for all (same headstamp/cartridge weight within .5 grs), LC12.

FED210 primers
41.6grs Varget
Nosler Accubond Long Range 190gr Part number 58456
2.83" OAL
2291FPS average

FED210 primers
42.7grs Varget
Sierra Match King (open tip) 168gr Stock Code 2200 (qty 100, plain, not moly)
2.83" OAL
2410FPS average

FED210 primers
49.1grs Varget
Barnes 130gr TTSX SKU: 30364
2.83" OAL
2906FPS average

FED210 primers
52grs CFE223
Hornady 125GMX Item number: 30190
2.83" OAL
2862FPS average

All four of those exhibit overpressure signs.
View Quote
I can tell you just based on the loads you listed that the 168gr OTM load is way under what "should" give pressure signs. I use the same brass, primer, and powder at 44.0gr seated to 2.815 COAL. Have you tried some factory FGMM to see if you get pressure suns with that too? I'd start there. If you do still get pressure signs, send the rifle in. Start eliminating variables. $20 for a box of factory ammo will tell you a lot.
Link Posted: 8/15/2017 12:20:12 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Motor1:


I can't help feeling the same. One other scenario is that the brass was fired in a really loose machine gun which stretched it excessively.

Twice sized brass should never look that close to failure (particularly that type of failure, head separation) there is something wrong here and it's not from being a little hot on the load data.

Motor
View Quote
That's essentially a myth. Every piece of brass I've reloaded in the past decade was shot through either a M60 or M240 (LC 89 or 12) and even had run marks from the links. It resizes fine. Even after a half dozen loadings they do not exhibit thinning at the web like in the pictures above. He needs to try factory ammo and rule that out.
Link Posted: 8/15/2017 12:22:14 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By borderpatrol:


Bingo! Lower your powder charge and look for accuracy instead.
View Quote
Those velocities are unacceptable for .308 though. He's getting AK velocities out of standard weight .308 projectiles...which already need as much help as they can get due to their low BC for longer ranges.
Link Posted: 8/15/2017 7:28:49 AM EST
You have two extremely over pressure loads according to the predictions from QuickLOAD if I have the numbers entered correctly. And they're very compressed at 109% and 116% powder capacity. Are you sure you have that right?







Link Posted: 8/15/2017 9:51:40 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By TripletDad:
You have two extremely over pressure loads according to the predictions from QuickLOAD if I have the numbers entered correctly. And they're very compressed at 109% and 116% powder capacity. Are you sure you have that right?

https://www.dropbox.com/s/iltxwdb1rcd647m/dyeager1.PNG?dl=1

https://www.dropbox.com/s/35mziqry99fh3m1/dyeager2.PNG?dl=1

https://www.dropbox.com/s/9a62yiq1xpofdlp/dyeager3.PNG?dl=1

https://www.dropbox.com/s/yur17s3q0u1ig4m/dyeager4.PNG?dl=1
View Quote
I promise you that a 168bthp over 42 gr of varget is not compressed. Something is wonky with the numbers...his or yours.
Link Posted: 8/15/2017 11:00:52 AM EST
[Last Edit: 8/15/2017 11:03:08 AM EST by popnfresh]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By cms81586:
I promise you that a 168bthp over 42 gr of varget is not compressed. Something is wonky with the numbers...his or yours.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By cms81586:
Originally Posted By TripletDad:
You have two extremely over pressure loads according to the predictions from QuickLOAD if I have the numbers entered correctly. And they're very compressed at 109% and 116% powder capacity. Are you sure you have that right?

https://www.dropbox.com/s/iltxwdb1rcd647m/dyeager1.PNG?dl=1

https://www.dropbox.com/s/35mziqry99fh3m1/dyeager2.PNG?dl=1

https://www.dropbox.com/s/9a62yiq1xpofdlp/dyeager3.PNG?dl=1

https://www.dropbox.com/s/yur17s3q0u1ig4m/dyeager4.PNG?dl=1
I promise you that a 168bthp over 42 gr of varget is not compressed. Something is wonky with the numbers...his or yours.
QL shouldn't be trusted for load density with Varget IME. Ive seen many common Varget loads listed that QL shows over 100%.
Link Posted: 8/15/2017 11:07:42 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By popnfresh:
QL shouldn't be trusted for load density with Varget IME. Ive seen many common Varget loads listed that QL shows over 100%.
View Quote
Yep. His loads are well under the Max minus 1gr (SOP for loading 7.62 brass vs .308 because reduced case capacity). He has a rifle issue unless his scale is off or he's doing something wonky with sizing his cases, which it doesn't sound like.
Link Posted: 8/15/2017 12:06:08 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By cms81586:


Yep. His loads are well under the Max minus 1gr (SOP for loading 7.62 brass vs .308 because reduced case capacity). He has a rifle issue unless his scale is off or he's doing something wonky with sizing his cases, which it doesn't sound like.
View Quote
His loads are at and probably over maximum for use in Lake City brass. 42.7 grains of Varget in a Lake City case with 168's seated to magazine length is case full +.

2400 fps from a 16" .308 shooting 168's is close to 2650 fps from a 24". This is 50 fps faster than maximum when using Lake City brass, in other words close to 1.0 whole grain over the top.

Maximum loads fired from a pressure test barrel using Lake City brass, 168 grain SMK's and Winchester or Federal 210M (match) primers are as follows:

41.5 grains of IMR-4064
40.5 grains of IMR-4895
40.0 grains of H4895
43.0 grains of WW-748
39.0 grans of IMR-3031

All of these loads hit maximum velocity between 2580 fps up to 2625 fps from a 24" bolt action barrel. Lake City brass limits velocity potential by almost 100 fps when compared to Winchester or Lapua brand .308 brass.

Varget and IMR-4064 have nearly identical burn rates. I would be very cautious increasing Varget charges over the 41.5 grains shown as maximum when loading IMR-4064. This load data is the end result of close to 1000 rounds being fired from several different test barrels using a Universal Receiver pressure gun. US government ballistician Wm. C. Davis Jr. conducted the tests. The OP is too hot IMO. His brass rims, primers and velocity all concur with my take on it.

My personal experience has found that some of the loads I listed above are too hot in some of my firearms. I have settled on 40.7 grains of IMR-4064 as being a maximum generic load in Lake City brass when using 168SMK's. I have thousands of rounds fired using that combination and it has been safe, reliable and accurate in every rifle I own. YMMV.
Link Posted: 8/15/2017 1:28:57 PM EST
I did verify the charge throw weight with another scale, not to mention calibrating both scales beforehand.

All loads are compressed to one degree or another, but the 130 load is obviously the most compressed due to the length of the solid bullet vs. lead core.

I think one of the things that is throwing me is that Hodgdon shows a maximum Varget charge with the SMK of 46grs. If you take the one grain rule of thumb, my load is nowhere near that. If you use 10%, it's closer, but still above what I can safely shoot.

Barnes data I can get much closer to their max (49.2grs Varget). Obviously different bullet/construction. But that load is ridiculously compressed...almost to the case mouth.

Please understand I'm not interested in pushing all of these to the max. I'm strictly trying to ensure what I'm experiencing is what I should be experiencing.
Link Posted: 8/15/2017 2:21:57 PM EST
[Last Edit: 8/15/2017 2:39:37 PM EST by cms81586]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By borderpatrol:


His loads are at and probably over maximum for use in Lake City brass. 42.7 grains of Varget in a Lake City case with 168's seated to magazine length is case full +.

2400 fps from a 16" .308 shooting 168's is close to 2650 fps from a 24". This is 50 fps faster than maximum when using Lake City brass, in other words close to 1.0 whole grain over the top.

Maximum loads fired from a pressure test barrel using Lake City brass, 168 grain SMK's and Winchester or Federal 210M (match) primers are as follows:

41.5 grains of IMR-4064
40.5 grains of IMR-4895
40.0 grains of H4895
43.0 grains of WW-748
39.0 grans of IMR-3031

All of these loads hit maximum velocity between 2580 fps up to 2625 fps from a 24" bolt action barrel. Lake City brass limits velocity potential by almost 100 fps when compared to Winchester or Lapua brand .308 brass.

Varget and IMR-4064 have nearly identical burn rates. I would be very cautious increasing Varget charges over the 41.5 grains shown as maximum when loading IMR-4064. This load data is the end result of close to 1000 rounds being fired from several different test barrels using a Universal Receiver pressure gun. US government ballistician Wm. C. Davis Jr. conducted the tests. The OP is too hot IMO. His brass rims, primers and velocity all concur with my take on it.

My personal experience has found that some of the loads I listed above are too hot in some of my firearms. I have settled on 40.7 grains of IMR-4064 as being a maximum generic load in Lake City brass when using 168SMK's. I have thousands of rounds fired using that combination and it has been safe, reliable and accurate in every rifle I own. YMMV.
View Quote
Not trying to argue, but aint no way. Out of a 16" SR-25 EMC I get 2510fps avg from a 178gr Hornady BTHP and 43.2gr of Varget. The load is compressed but not to the extent powder extends into the neck of the case. Charged with a funnel and drop tube. That's with a significantly heavier bullet and a half a grain more powder. From a 24" barrel 2650fps is nowhere near the max pressure velocity for 168's. I'm pushing 175's faster than that into the 2700fps range from a slightly longer barrel (26"...so maybe 40fps faster than a 24" barrel) with minimal pressure signs (slightly flattened primer...no heavy bolt lift) and great accuracy. Yes...every rifle is different (that's why we do a ladder test), and so is every reloading manual, but most all manuals list the max charge for a 168gr bullet at over 45gr for Varget...

OP needs to shoot some factory FGMM and see what his brass looks like. He's never fired factory ammo through the rifle, and cannot jump straight to a load data issue if he's not sure the rifle doesn't have a problem. He's seeing too many brass issues all at once...and no way he should be getting case separations on the second firing of LC brass (with the first being the original firing). Unless this was used up brass that was sold to him as once fired, he may something serious going on with his rifle and that needs to be validated with an ammunition of known quality.

Attachment Attached File
Link Posted: 8/15/2017 3:06:08 PM EST
What has been lost in this discussion is the fact that published load data is developed using Winchester, Federal or some other brand of commercial brass. You cannot reference it when using Lake City brass, it doesn't work.

The OP is using a semi-auto rifle which further reduces the amount of powder that can be safely loaded. These two factors in combination create the problems he's experiencing. Case rims getting ripped from case head is too much gas too soon in the cycling process. Flattened primers and firing pin extrusion marks can be caused by oversized firing pin holes, high pressure or both.

The data I posted as maximum charge weights for 168 grain bullets loaded in Lake City brass are the actual findings of one of the most famous ballisticians of the 20th Century. He was a scientist and was concerned only with the facts, not wishful thinking.

If you are getting higher velocities using these components from a 24" barrel you're doing so with higher pressures as well. 60 fps represents approximately 1.0 grains of powder in .308. This rule of thumb (60 fps per grain) only holds true with safe loads. Once you go over things get unpredictable.

I have used Mr. Davis's load data for close to 30 years without problems earning my NRA Master card in 1989 shooting a M1-A. His loads work and won't cause problems. People are free to experiment all they want, but the work has already been done on the safety parameters. My goal is to get people to use them.
Link Posted: 8/15/2017 3:26:23 PM EST
Originally Posted By cms81586:
I promise you that a 168bthp over 42 gr of varget is not compressed. Something is wonky with the numbers...his or yours.
View Quote
42.0gr of Varget shows a load density of 99.6% with that case volume, powder and bullet. I agree, these numbers are not exact. I'm not saying compressed is bad, but at 110% and over, you have serious crunchies going on. Seating those might even be deforming the bullet.

There's no way I'd let these two loads near my rifles, they're pretty much proof loads and no wonder they're showing issues. If I had any left, I'll pull them and salvage the components.
    41.6grs Varget, Nosler Accubond Long Range 190gr Part number 58456, 2.83" OAL, 2291FPS average, 2391 fps predicted
    49.1grs Varget, Barnes 130gr TTSX SKU: 30364, 2.83" OAL, 2906FPS average, 2910 fps predicted



The other two loads aren't anything worse than what I do run as far as predicted pressures.
    42.7grs Varget, Sierra Match King (open tip) 168gr Stock Code 2200 (qty 100, plain, not moly), 2.83" OAL, 2410FPS average, 2388 predicted
    52grs CFE223, Hornady 125GMX Item number: 30190, 2.83" OAL, 2862FPS average, 2977 predicted.


What I can't figure out is why 2 predictions for Varget are fairly close, but one of the high pressure loads is 100fps slow. The CFE223 load is slow too.

My LC-11 LR brass that I've been using in my rifle has an average case capacity of 55.0 grains after firing. The TTSX-BT load with the 54.0gr capacity I was given, that shows 69761psi. With a 55.0gr brass/chamber it goes down to 66283psi which is still over max. Book max on a .308 Winchester is 62000 psi. When I change from 308 to 7.62 NATO, the case capacity goes down to 52.00 grains of water according to QL and the max pressure goes up to 80917psi with a predicted velocity of 3006fps.

Not having an AR-10, I don't know if they're chambered in .308 or 7.62, but I won't go higher than a predicted value of 55000psi which will work fine for both. 70K and 80K psi is going to wear out or cause the gun to self disassemble IMO.
Link Posted: 8/15/2017 4:23:02 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By TripletDad:

42.0gr of Varget shows a load density of 99.6% with that case volume, powder and bullet. I agree, these numbers are not exact. I'm not saying compressed is bad, but at 110% and over, you have serious crunchies going on. Seating those might even be deforming the bullet.

There's no way I'd let these two loads near my rifles, they're pretty much proof loads and no wonder they're showing issues. If I had any left, I'll pull them and salvage the components.
    41.6grs Varget, Nosler Accubond Long Range 190gr Part number 58456, 2.83" OAL, 2291FPS average, 2391 fps predicted49.1grs Varget, Barnes 130gr TTSX SKU: 30364, 2.83" OAL, 2906FPS average, 2910 fps predicted



The other two loads aren't anything worse than what I do run as far as predicted pressures.
    42.7grs Varget, Sierra Match King (open tip) 168gr Stock Code 2200 (qty 100, plain, not moly), 2.83" OAL, 2410FPS average, 2388 predicted52grs CFE223, Hornady 125GMX Item number: 30190, 2.83" OAL, 2862FPS average, 2977 predicted.


What I can't figure out is why 2 predictions for Varget are fairly close, but one of the high pressure loads is 100fps slow. The CFE223 load is slow too.

My LC-11 LR brass that I've been using in my rifle has an average case capacity of 55.0 grains after firing. The TTSX-BT load with the 54.0gr capacity I was given, that shows 69761psi. With a 55.0gr brass/chamber it goes down to 66283psi which is still over max. Book max on a .308 Winchester is 62000 psi. When I change from 308 to 7.62 NATO, the case capacity goes down to 52.00 grains of water according to QL and the max pressure goes up to 80917psi with a predicted velocity of 3006fps.

Not having an AR-10, I don't know if they're chambered in .308 or 7.62, but I won't go higher than a predicted value of 55000psi which will work fine for both. 70K and 80K psi is going to wear out or cause the gun to self disassemble IMO.
View Quote
.

I'm using the 168 gr load as a reference since it's the only one if the projectiles he listed which I have significant experience with. It's certainly within the realm of being a moderate/reasonable powder charge.

I'll still reiterate though...OP needs to shoot some factory ammo to rule out rifle issues.
Link Posted: 8/15/2017 4:32:36 PM EST
[Last Edit: 8/15/2017 4:36:10 PM EST by cms81586]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By borderpatrol:
What has been lost in this discussion is the fact that published load data is developed using Winchester, Federal or some other brand of commercial brass. You cannot reference it when using Lake City brass, it doesn't work.

The OP is using a semi-auto rifle which further reduces the amount of powder that can be safely loaded. These two factors in combination create the problems he's experiencing. Case rims getting ripped from case head is too much gas too soon in the cycling process. Flattened primers and firing pin extrusion marks can be caused by oversized firing pin holes, high pressure or both.

The data I posted as maximum charge weights for 168 grain bullets loaded in Lake City brass are the actual findings of one of the most famous ballisticians of the 20th Century. He was a scientist and was concerned only with the facts, not wishful thinking.

If you are getting higher velocities using these components from a 24" barrel you're doing so with higher pressures as well. 60 fps represents approximately 1.0 grains of powder in .308. This rule of thumb (60 fps per grain) only holds true with safe loads. Once you go over things get unpredictable.

I have used Mr. Davis's load data for close to 30 years without problems earning my NRA Master card in 1989 shooting a M1-A. His loads work and won't cause problems. People are free to experiment all they want, but the work has already been done on the safety parameters. My goal is to get people to use them.
View Quote
Loads tailored to M1A's are notoriously slow due to the design of the rifle and op rod concerns. An AR-10 can handle much faster velocities. Everyone is convinced this is a powder charge issue....all I'm saying is I'm not convinced until the OP shoots some factory ammo and checks his brass and velocities. A box of FGMM 168gr will yield faster velocities than he is getting with his 168gr handload (which is showing pressure signs). The numbers aren't adding up... he needs a baseline.
Arrow Left Previous Page
Page / 2
Top Top