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9/22/2017 12:11:25 AM
Posted: 8/25/2010 6:23:43 PM EDT
I put together a White Oak 18" upper back when the 6.8 was just barely catching on. It's the original chamber specs and 1x10 twist so it's pretty old school. I messed with it for awhile but never could get anything close to what Remington claimed with the cartridge. I seem to recall that the original published velocities were close to 2,800 fps with the 115gr BTHP bullet.

Fast forward a couple of years and now everybody is building these with a Spec II chamber and a 1x11 twist. I talked to John Holliger at White Oak and he says he can easily ream my chamber to Spec II and doesn't see any real reason to ditch my old 1x10 barrel.

So, my question is twofold. Does the Spec II chamber really change the ballistics of the cartridge or am I really only going to see some modest gains in velocity? And can I realize these gains with factory ammo? I know SSA claims to have improved the cartridge's performance but I'm somewhat skeptical.

What say those of you with time on both chambers?


TIA!
Link Posted: 8/25/2010 7:11:24 PM EDT
[Last Edit: 8/25/2010 7:13:52 PM EDT by AR-Performance]
Link Posted: 8/25/2010 7:25:24 PM EDT
[Last Edit: 8/25/2010 7:30:28 PM EDT by bobweaver]
If you want to shoot SSA tactical loads then I would do it. As for the 1/10 twist, my RRA 1/10 out shoots my two buddy's 1/11's so I don't feel it is necessary. That said, my ARP Viking upper built by H, the man that posted above me, out shoots my RRA. If you have any questions he is the one to ask. H, the Viking has performed flawlessly and will be taking its first hog this weekend
Link Posted: 8/25/2010 7:48:12 PM EDT
As I understand it the spec II chamber creates less pressure when firing the same ammo. If this is true then reaming out to a spec II chamber might be considered a safety feature when it comes to shooting some of the hotter loads sold by SSA.

There is a thread around somewhere called the state of the 6.8 that outlined the changes of the spec II chamber.
Link Posted: 8/25/2010 7:58:40 PM EDT
Link Posted: 8/25/2010 9:11:58 PM EDT
Originally Posted By mort:
As I understand it the spec II chamber creates less pressure when firing the same ammo. If this is true then reaming out to a spec II chamber might be considered a safety feature when it comes to shooting some of the hotter loads sold by SSA.

There is a thread around somewhere called the state of the 6.8 that outlined the changes of the spec II chamber.


This. The chamber was modified to correct an error on the original blueprints and to reduce pressure, allowing handloaders to extract a few more fps. Some manufacturers also went with the slower twists (1:11 or 12) and fewer grooves.

All factory loads except for (maybe) the hotter SSA Tac loads are OK.

Others, like LWRC figured out how to address the pressure issues and keep the more versatile 1:10 twist and 6-groove rifling. Others like LMT retained the Spec I chamber and can still shoot SSA Tac.

You can ream the chamber to SPEC II but there is anecdotal and "logical" evidence to suggest that reaming a chromelined chamber/barrel may not turn out satisfactorily.

Link Posted: 8/26/2010 6:52:52 AM EDT
Just rebarrel your upper. Done.
Link Posted: 8/26/2010 7:04:44 AM EDT
Improvement is always worth it.

While I have three 6.8 SPC guns, I don't shoot them enough due to ammo cost.

Yeah, I know.....reload your own.
Link Posted: 8/26/2010 7:28:48 AM EDT
Link Posted: 8/26/2010 7:37:47 AM EDT
Originally Posted By AR-Performance:
Just reaming the chamber will not add velocity with the same loads.
SSA's commercial 110 prohunters hit 2550-2600 depending on the rifling(land:groove ratio) Hornadys 110gr HPBT will hit the same as SSA's commercial loads(2550-2600).
SSA's Tac loads are not as fast as the old "Combat" loads were, the new "TAC" loads may be 50fps faster than the commercial loads or 2600-2650.
Where the better specs come into play is if you reload and want better performance, better trajectory and better terminal performance at longer ranges.
In a good spec 16" barrel you could get 2800fps with the same weight bullets by reloading with stiffer charges of powder but it takes more than just reaming a 10 twist barrel.



2800 fps with a 110gr bullet is pretty impressive and is what Remington touted the 6.8 as being able to do back in the old days. What does that do, wear wise, to a rifle that was designed to shoot a .22" bullet? Surely you must be using heavy buffers, etc.

Along the same lines; doesn't the cartridge lose some of its versatility with the change to a slower twist barrel? Staying within the confines of the magazine, I seem to recall that I could get a 130gr softpoint bullet to cruise along at 2050-2100 fps from my SAAMI chambered 18" barrel. This isn't a rocket by any means but it would seem to be a good choice depending on your intended quarry. Will the 11.25" or whatever twist stabilize a heavier projectile? If I stick with what I’ve got (1x10 four groove barrel) I’m only gaining 25-50 fps? I don’t see that small increase as being worth the expensive of shipping, reaming, return shipping and the like and it still leaves me with the ability to shoot a wider variety of bullets.

I guess what I'm asking is, at the end of the day, aren't we still burning 28 grains of powder? I know some people want to think that you can turn an AR into a .270 Winchester but I just don't see that being a realistic expectation based on case size, available powder and the laws of physics.

Link Posted: 8/26/2010 8:34:09 AM EDT
[Last Edit: 8/26/2010 8:37:47 AM EDT by AR-Performance]
Link Posted: 8/26/2010 5:08:01 PM EDT
Originally Posted By AR-Performance:
In the end it is what you want to get out of your rig, some are perfectly happy with shooting factory ammo, some of us like to shoot through hogs...long ways.
BTW SSA's commercial loads burn 30.5gr in the 110gr loads.


I'd imagine the 30.5gr of whatever powder SSA is using is pretty much all that case will allow. Increasing freebore and changing barrel twists might give some advantage but the case capacity is, ultimately, the deciding factor on what can be achieved. Weatherby certainly made a whole line of guns and cartridges based on freebore and pushing chamber pressures to the limit. But does the .340 Weatherby really offer any true advantage over the .338 Winchester Magnum? I know it kicks a hell of a lot more, that's for sure!

In perusing the latest data from Hodgdon and Alliant, I see that they're listing 100-110gr bullet loads that are pushing 2,700 and 2,800 fps. Of course these loads are probably developed using a 20" test barrel. Anyway, I haven't loaded anything in 6.8 in probably five years and it looks like maybe I just need to try some of the current loading data and give the cartridge another chance.

Rebarreling is not an option, as I feel I've already spent more on my upper than it will ever be worth. Dropping another $300+ to get an additional 50fps just isn't worth it at this point.



Link Posted: 8/26/2010 5:28:03 PM EDT
Originally Posted By Melvin_Johnson:
Originally Posted By AR-Performance:
In the end it is what you want to get out of your rig, some are perfectly happy with shooting factory ammo, some of us like to shoot through hogs...long ways.
BTW SSA's commercial loads burn 30.5gr in the 110gr loads.


I'd imagine the 30.5gr of whatever powder SSA is using is pretty much all that case will allow. Increasing freebore and changing barrel twists might give some advantage but the case capacity is, ultimately, the deciding factor on what can be achieved. Weatherby certainly made a whole line of guns and cartridges based on freebore and pushing chamber pressures to the limit. But does the .340 Weatherby really offer any true advantage over the .338 Winchester Magnum? I know it kicks a hell of a lot more, that's for sure!

In perusing the latest data from Hodgdon and Alliant, I see that they're listing 100-110gr bullet loads that are pushing 2,700 and 2,800 fps. Of course these loads are probably developed using a 20" test barrel. Anyway, I haven't loaded anything in 6.8 in probably five years and it looks like maybe I just need to try some of the current loading data and give the cartridge another chance.

Rebarreling is not an option, as I feel I've already spent more on my upper than it will ever be worth. Dropping another $300+ to get an additional 50fps just isn't worth it at this point.



It is worse than that. The Hodgdon data were shot in a 24-inch barrel. The Hornaday and Sierra reloading manuals, which show data for 16-inch barrels, show velocities for 110-115gr bullets at about 2500-2600 fps.

320pf
Link Posted: 8/26/2010 5:31:32 PM EDT
[Last Edit: 8/26/2010 5:31:49 PM EDT by Melvin_Johnson]


It is worse than that. The Hodgdon data were shot in a 24-inch barrel. The Hornaday and Sierra reloading manuals, which show data for 16-inch barrels, show velocities for 110-115gr bullets at about 2500-2600 fps.

320pf


So a 320 power factor is still not obtainable?
Link Posted: 8/26/2010 5:55:34 PM EDT
Originally Posted By Melvin_Johnson:


It is worse than that. The Hodgdon data were shot in a 24-inch barrel. The Hornaday and Sierra reloading manuals, which show data for 16-inch barrels, show velocities for 110-115gr bullets at about 2500-2600 fps.

320pf


So a 320 power factor is still not obtainable?


You can get close with 130 gr bullets in a 20 inch barrel. Step up to a 24-inch and you probably could just make it.

320pf
Link Posted: 8/27/2010 7:25:28 AM EDT
Link Posted: 8/27/2010 8:08:10 AM EDT
Originally Posted By Forest:
Originally Posted By Melvin_Johnson:


It is worse than that. The Hodgdon data were shot in a 24-inch barrel. The Hornaday and Sierra reloading manuals, which show data for 16-inch barrels, show velocities for 110-115gr bullets at about 2500-2600 fps.

320pf


So a 320 power factor is still not obtainable?


130s in an 18" barrel will net you MPF.


Yes they will...
Link Posted: 8/27/2010 10:30:18 AM EDT
Originally Posted By QuicksilverJPR:
Originally Posted By Forest:
Originally Posted By Melvin_Johnson:


It is worse than that. The Hodgdon data were shot in a 24-inch barrel. The Hornaday and Sierra reloading manuals, which show data for 16-inch barrels, show velocities for 110-115gr bullets at about 2500-2600 fps.

320pf


So a 320 power factor is still not obtainable?


130s in an 18" barrel will net you MPF.


Yes they will...


Actually one of the reasons I initially got interested in the 6.8 was for major power factor. Some of the original loadings showed major being obtainable with a 130gr bullet but I never really could get close. But I also seem to recall that this was back when major was 340 with the rifle.

Anyway, are you guys getting a consistant power factor with room for error?

Link Posted: 8/27/2010 10:54:12 AM EDT
Link Posted: 8/27/2010 10:57:30 AM EDT
Originally Posted By Forest:
Originally Posted By Melvin_Johnson:
Anyway, are you guys getting a consistant power factor with room for error?



Room for error? Yes.

The real issue is how good your barrel is (chamber and rifling).

You need to use small primered brass, and the life is VERY short.

Powder selection is also critical. I can't reliably do it with H322, it's possible with some lots but not others. RL-10X seems the best options, with the Speer 130 SP (I've come close with the Sierra 130gr SP flat base).


I haven't tried any powder other than 10X. I'm not sure of any others (well, ones in standard use with the 6.8) that would work other than maybe H335, but even then...
Link Posted: 8/27/2010 10:57:42 AM EDT
I have three answers to your questions.
1. Yes it's worth it.
2. Go to 68forums and quit wasting time here for up to date info on the 6.8.
3. The decision is ultimately yours. You seem to be , ( intentionally or not, or maybe I'm just picking up on it wrong, so forgive me ), argumentative with Harrison from AR Performance. I would listen closely to what he has to say, and check his posts on 68forums. His word is gold when it comes to performance in the 6.8, and has been responsible for many of the gains that the 6.8 has achieved over the disaster that was the initial spec barrels and chambers.
Link Posted: 8/27/2010 10:59:53 AM EDT
Forest, I've already got four loads on some of my SSA brass, with no signs if degradation whatsoever. I have read of several getting close to ten loads, including H.
Link Posted: 8/27/2010 11:24:11 AM EDT
I shoot some pretty warm loads, and I am getting 8––10 loads out of some lots of brass. The thickness of SSA brass has actually changed a few times as material got almost impossible to get and other forces necessitated a slight change.

I also have some brass going to Rick Lull @ Old Dominion cartridge. He is examining the brass from different lots so that we might get a better idea of overall or average life. We cull out any that have incipient case head separation or cracked necks.

Forest, from my records, it looks like we have not culled any that had less than 5 loads per case. Granted, I do not load the 130's, but I do shoot the 110 Accubonds with compressed charge of 10X. I believe those go at least 4-5 loads as well. If you use the same powder charge with the Barnes 110 TTSX, you get longer life. Why? Because the rings on that bullet reduce bearing surface and chamber pressure. I believe we can also extrapolate this to rifling designs which reduce that bearing contact.

I will update as I go along, but I am here to tell the OP that there is a difference in the loads I can shoot in my ARP 12 twist 3 groove, versus SAAMI, 10 twist guns, period. We are talking about 200 or so FPS. That barrel will take pressure to the point where I cannot actually get enough of most powders into a case to cause serious pressure problems. Not all 6.8 (this happens in many other calibers, too) barrels will do this. Its design is specifically intended to reduce pressure. Oh, and BTW, it also happens to shoot ragged holes at 100 yards.

In my somewhat educated opinion, if you start with SAAMI, 10 twist, 6 groove, you will see pressure signs sooner in the ascent up the charge ladder versus similar loads fired from barrels with longer leade, slower twist, and less restrictive rifling designs.



Link Posted: 8/27/2010 11:30:47 AM EDT
Maybe you're the culprit I was thinking about HTR.
Link Posted: 8/27/2010 11:33:35 AM EDT
Link Posted: 8/27/2010 11:38:14 AM EDT
Link Posted: 8/27/2010 12:07:35 PM EDT
Originally Posted By Forest:
Originally Posted By QuicksilverJPR:
I haven't tried any powder other than 10X. I'm not sure of any others (well, ones in standard use with the 6.8) that would work other than maybe H335, but even then...


I have easy access to H335 and H322 so those were my first attempts.


I have boatloads of 10X, RE7 and H335...

Lots of my guns shoot the same powders, thank goodness!
Link Posted: 8/27/2010 12:13:50 PM EDT
I used to think of H322 tolerating compression pretty well, but I saw the same lot-to -lot variability and I have been disappointed with H322 and the 95 TTSX / 110 Accubond. I have not gotten nearly the accuracy from H335 as I do with 10X.

For now, I'm sticking with 10X for the heavier weight bullets.
Link Posted: 8/27/2010 5:50:20 PM EDT
While we've started to drift off onto the topic of heavy bullets and USPSA major power factor; have any of you guys used anything heavier than 130gr bullets? Are any of the flat based bullets short enough to seat to magazine length?

Of course running a 150gr bullet at only 2200fps is going to give you a trajectory that more of a rainbow than an arc...

Link Posted: 8/27/2010 5:53:33 PM EDT
Originally Posted By pavlovwolf:
I have three answers to your questions.
1. Yes it's worth it.
2. Go to 68forums and quit wasting time here for up to date info on the 6.8.
3. The decision is ultimately yours. You seem to be , ( intentionally or not, or maybe I'm just picking up on it wrong, so forgive me ), argumentative with Harrison from AR Performance. I would listen closely to what he has to say, and check his posts on 68forums. His word is gold when it comes to performance in the 6.8, and has been responsible for many of the gains that the 6.8 has achieved over the disaster that was the initial spec barrels and chambers.


If I've come across as argumentative that wasn't my intent.

I'm just trying to ask a question on a forum that gets alot more traffic from alot more "rounded" folks.
Link Posted: 8/30/2010 10:18:57 AM EDT
Originally Posted By Melvin_Johnson:
While we've started to drift off onto the topic of heavy bullets and USPSA major power factor; have any of you guys used anything heavier than 130gr bullets? Are any of the flat based bullets short enough to seat to magazine length?

Of course running a 150gr bullet at only 2200fps is going to give you a trajectory that more of a rainbow than an arc...



It'll give you the trajectory of a 762x39 pretty much, with a heavier bullet...
Link Posted: 8/30/2010 11:15:15 AM EDT
I've loaded just about every bullet that will fit into the 6.8 X 43 mm case, in cluding the massive 150 Woodleigh weld-core. I still use the 150grain Sierra Game King for subsonics, and, in that use, the extra bullet length is a realtive advantage because it decreases free case volume, but is still short enough to stabilize in a 10 twist barrel.

Otherwise, the 150's are long enough that you end up wih the expected problem. That is, in order to get them to magazine length, you end up with excessive powder compression or reduced case capacity, and most often both. This results in reduced velocity, and increased pressure that just isn't worth the effort.

Time and time again, we see the best performance in the 6.8 from lighter, faster projectiles. This cartridge tends to belie some of the conventional wisdom we grew up wth. Big feral hogs don't seem to understand what MPF is.....
Link Posted: 9/4/2010 3:20:44 AM EDT
Thanks for all the info. I've borrowed a SPCII reamer from a board member and will be using it shortly.


Link Posted: 9/4/2010 11:14:09 PM EDT
That's good to hear MJ. I didn't mean to come across as an a**hole. I think you'll really be happy with what your rifle will be capable of after you ream the chamber.
Link Posted: 9/5/2010 2:55:23 PM EDT
I have a RRA 6.8.
http://www.rockriverarms.com/index.cfm?fuseaction=category.display&category_id=247

It is about 2 years old now. I shoot the SSA Comercial loads with NO problems.
For my purpose the combat loads are just not needed.
With that said, I have shot combat loads. I have not seen a bit of difference.
Link Posted: 9/5/2010 3:16:18 PM EDT
For sure get it reamed. You can then use the 1/10 untill you get another one.
Link Posted: 9/5/2010 4:38:36 PM EDT
With the longer leade in mind, is there going to be any loss of accuracy? Most people agree that the more the bullet has to jump, the less accurate a given load is going to be.
Link Posted: 9/5/2010 5:35:23 PM EDT
YMMV depending on the individual barrel, but sub MOA is common with the SPC2 chamber.
Link Posted: 9/11/2010 1:21:34 AM EDT
i can't wait to finish my upper with the spc2.
Originally Posted By bedlamite:
YMMV depending on the individual barrel, but sub MOA is common with the SPC2 chamber.


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