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4/22/2019 5:32:20 PM
Posted: 4/28/2015 10:53:36 PM EDT
[Last Edit: 4/29/2015 12:05:33 AM EDT by ceesthadees]
Hey guys. I am a long time member but do not post much. I am basically a lurker.

I am a recent 300 BO owner, with a lot of experience in shooting and reloading for pistols, and to a lesser extent, but no novice, with semis (M1A, AR-15).

For the life of me, I cannot figure out why my reloads are making and depositing this copper ring at the beginning of the throat. I cannot duplicate the problem with commercial rounds.



After a couple of the rings get deposited, I will get a FTF.

Load Specs
Bullet: SMK 125gr OTM #2121
Brass: LC '07'ish converted brass (purchased, re-sized with Dillon carbide die), neck thickness is okay, as far as my caliper can determine
Powder: IMR 4227 18.7gr Crimp: Very light (1/4 turn) with Dillon crimp die
Case Length: 1.36
COAL: 2.22

Notes: Rifle headspace is pretty tight. Pretty much anything over the minimum with my Wilson gauge will FTF, or will be difficult to remove manually after being chambered with a full bolt release.

(continued on next post)
Link Posted: 4/28/2015 10:59:05 PM EDT
[Last Edit: 4/28/2015 11:49:13 PM EDT by ceesthadees]
Sorry about the pictures. I need some more posts!

Headspace check on reloads

Length check on reloads


Pressure check on reloads


Headspace check on commercial


Length check on commercial


COAL of commercial ammo is 2.24+

Barrel is an AeroPrecision 300BO 16" pistol.

I have talked the Aero and, of course, they have never seen anything like this before. I have seen some other threads on the interwebtooby, but not a lot about the resolution.




Link Posted: 4/28/2015 11:06:34 PM EDT
[Last Edit: 4/28/2015 11:07:44 PM EDT by dryflash3]
Link Posted: 4/28/2015 11:09:03 PM EDT
Are you chamfering the cases? I suspect that copper ring is scraped off during seating.
Link Posted: 4/28/2015 11:12:48 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By wingsnthings:
Are you chamfering the cases? I suspect that copper ring is scraped off during seating.
View Quote
Yes, the cases are chamfered before seating. I have made probably a couple of dozen test rounds and then pulled the bullets. I have yet to see a damaged bullet.
Link Posted: 4/28/2015 11:15:24 PM EDT
Link Posted: 4/28/2015 11:15:54 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By dryflash3:
Are you forming your own cases from 223?

Are you deburring the inside of the case before seating the bullet?


eta, post up your pics, I will approve them. I don't do copy paste to see pics.
View Quote
Thanks for posting pics.

The brass was commercial, so the mouths were pretty good to start. I have chamfered the mouth inside anyway when I first saw this problem.
Link Posted: 4/28/2015 11:32:31 PM EDT
Link Posted: 4/28/2015 11:51:39 PM EDT
[Last Edit: 4/28/2015 11:56:16 PM EDT by ceesthadees]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By dryflash3:
I approved pics in second post, but don't see them.

Pic in first post is fine.


Can you pick that ring off after you seat the bullets?


Did you debur the outside of the case?
View Quote
I think the photobucket library is fixed.

The ring does not exist before firing, so there is no ring to remove after seating the bullet.

Yes sir, I did debur the outside.


Link Posted: 4/28/2015 11:58:51 PM EDT
[Last Edit: 4/29/2015 12:01:26 AM EDT by RamblinWreck]
I suspect your cases are a smidge too long, or chamber neck is a smidge out of spec. Thats what I would look at first. You don't show case length...

ETA: maybe too hard a crimp is ripping off, Are you roll crimping? Need to taper crimp if you are.
Link Posted: 4/29/2015 12:05:02 AM EDT
[Last Edit: 4/29/2015 12:06:40 AM EDT by ceesthadees]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By RamblinWreck:
I suspect your cases are a smidge too long, or chamber neck is a smidge out of spec. Thats what I would look at first. You don't show case length...

ETA: maybe too hard a crimp is ripping off, Are you roll crimping? Need to taper crimp if you are.
View Quote
Thanks for the heads up on case length (1.36). I fixed first post.

I am putting a 1/4 turn taper crimp with the Dillon taper crimp die.
Link Posted: 4/29/2015 12:18:24 AM EDT
can ya pull a couple and see if there is a ring present? sometimes its almost "tucked" into the chamfer.
Link Posted: 4/29/2015 2:45:15 AM EDT
I don't know what causes those rings but I have seen them before on .308 Remington 700 s with 168 FGM. They did not seem to cause any function or accuracy problems.
Link Posted: 4/29/2015 6:24:27 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By mb3:
I don't know what causes those rings but I have seen them before on .308 Remington 700 s with 168 FGM. They did not seem to cause any function or accuracy problems.
View Quote

Happened when my rebarreled Mauser was breaking in also.
Link Posted: 4/29/2015 10:12:48 AM EDT
[Last Edit: 4/29/2015 10:22:58 AM EDT by ceesthadees]
I just loaded and pulled 10 rounds. The bullets look okay and there was no residual brass or copper left in the puller.




Link Posted: 4/29/2015 10:36:34 AM EDT
[Last Edit: 4/29/2015 10:37:12 AM EDT by ceesthadees]
Is it possible that the barrel is not cut correct and for whatever reason the SMK's indicate the problem while different profile bullets do not? I need to track down some commercial ammo with SMK 125 OTMs.
Link Posted: 4/29/2015 1:58:30 PM EDT
Link Posted: 4/29/2015 3:16:48 PM EDT
[Last Edit: 4/29/2015 3:25:51 PM EDT by RamblinWreck]
There are several easy ways to check bullet max oal for an individual barrel. I take a sized case and cut a slit down the neck with a thin moto cut-off wheel so the bullet is held tight but still slips with a little pressure. That way you can "soft seat" it and measure the OAL at the lands.
1.Remove extractor and ejector from bolt, make sure chamber/barrel is clean. This is done with upper off the lower on the bench. Unloaded.
2.Insert the bullet you are measuring just into the case, long, and put a little Imperial sizing wax or other slippery agent on it. Put in chamber and push carrier until bolt closes to seat the bullet at the lands.
3.Retract carrier, and carefully, gently push out the test round with a cleaning rod from the muzzle.
4. Measure OAL with calipers, or with comparator tool for that caliber, and record it.

Do this with 5-10 random bullets out of the box of bullets you are measuring to get an average. The length will be your "hard-at-the-lands" COL for that bullet, or max OAL, for this barrel. I usually set the seater die about 0.025 shorter than that because pressures go up fast when the bullet is jammed into the lands, and you definitely don't want ammo that long in a gas gun, no. For VLDs in bolt guns you sometimes want the bullet at the lands, or even in a little, but for semi NEVER.

Sometimes this max measured OAL is longer than mag length and you have to seat shorter anyway.Or, like in High Power, we single load at 600 yards anyway, so we don't care if we seat a Sierra 80 long.

HTH
Link Posted: 4/29/2015 8:41:23 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By dryflash3:
Just reread your first post, you are using 2.22 as your OAL.

I believe that is too long.

OAL should be set by measuring bullet ogive at .250 and centering that point at the front mag bump.

Sorry but every time I post that pic it gets stolen so I don't post that any more. See AAC's website for more info.

Don't have my notes in front of me, but thinking the OAL should be in the 1.90 range.

I also trim my cases to 1.360 as I like even numbers. Your trim length is fine.

Your pics are showing up fine.
View Quote
SAAMI http://www.saami.org/pubresources/cc_drawings/Rifle/300%20AAC%20Blackout.pdf says 2.260 is max. Additionally I have successfully test shot longer commercial loads. The Sierra load (the infamous floating around the web pdf manual, uses something like 2.21 COAL.

Please tell me I did not make a mistake on something as mundane as the length.

Plus, what do you mean that you picture gets stolen? Used without your permission or acknowledgement?


Link Posted: 4/29/2015 8:45:04 PM EDT
[Last Edit: 4/29/2015 8:45:51 PM EDT by ceesthadees]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By RamblinWreck:
There are several easy ways to check bullet max oal for an individual barrel. I take a sized case and cut a slit down the neck with a thin moto cut-off wheel so the bullet is held tight but still slips with a little pressure. That way you can "soft seat" it and measure the OAL at the lands.
...
Sometimes this max measured OAL is longer than mag length and you have to seat shorter anyway.Or, like in High Power, we single load at 600 yards anyway, so we don't care if we seat a Sierra 80 long.

HTH
View Quote
Thanks for that technique description. Let's just say my technique was not near as elegant as yours and leave it at that.

For my gun, (I think all 300's ??) you have to exceed max length for the mag and go below the minimum bullet seating depth to reach the lands.
Link Posted: 4/29/2015 8:54:47 PM EDT
[Last Edit: 4/29/2015 8:55:55 PM EDT by ceesthadees]
I think I may be on to something....

Take a look at this load's powder compression. The powder level is at approximately the top of the black line.



This is certainly more compression than the rule of thumb 10%. I have backed off from 18.7 to 18.2 of 4227 and shot 6 rounds with no ring. Kind of hoping this is not the issue because I have three pounds of 4227. I only have about 1/2 pound of the very elusive H110 (unless I pull a bunch of .44 mags). I will shoot some more of this new load and hope I do not see any more copper rings.

Perhaps, now I am just making stuff up, the longer contact with the flame/heat was causing the bottom of the bullet to fail??
Link Posted: 4/29/2015 11:15:46 PM EDT
[Last Edit: 4/30/2015 10:40:14 AM EDT by dryflash3]
Link Posted: 4/30/2015 7:25:59 AM EDT
Gotcha on the length. On the other two semis I load, I use the "long as possible" method to pretty good success. That is why I came to the experts here for answers!

Unfortunately I am leaving town for work for a few weeks and will not be able to try the new length but will update as soon as I have some results.
Link Posted: 4/30/2015 10:45:15 AM EDT
Link Posted: 4/30/2015 12:09:23 PM EDT
[Last Edit: 4/30/2015 12:59:50 PM EDT by ceesthadees]
Huh, I am thinking I should have known that before starting to reload for the 300. Thanks a ton, df.


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