New BRA piercing primers - help diagnosing cause?

[dnellans]

After lots of reading on here I decided to spin up a BRA based on @Alex Wheeler #1 JGS. It is my first time with an Ackley and I'm only "a few" barrels into doing my own versus the 10's of thousands you guys have all probably done over the years so looking for some advice on if I've gone horribly offtrack somewhere or its just a load issue...

Since it was my first time messing with an Ackley of any type I wasn't super confident about spacing off a 6br guage. So I had manson make me a go guage and le wilson make me a case gauge just to be able to double check everything.

Here are some of the details (and please ask for more if needed):

Spaced it off the Manson go gauge and cut a little deeper than intended (still a rookie) but its not absurdly deep. Measured using depth mic+go as well as shims behind go on borden action. Measures to .003 and will very hard close on .003 shim but no way on .004.

No turn reamer but skim turned necks (on unfired BR brass) are .2670 loaded and .2715 after fire form - so I don't think there is a neck clearance issue.

This is where I get a little concerned with the measurments...

Unfired BR brass will hard close on .011 worth of shim which says there is a fair bit of space in there, versus a tight fit at the neck shoulder junction. However, this isn't outside my experience on how short unfired factory fresh brass can be, so I decided to load the brand new BR cases with a .010 jam into the lands and go for it.

Looking around a bit it looks like folks talk about as much as 29.5gr of H4895 behind 105's as their fire forming load. I decided to be more conservative and started at 28.5 just in case. 10 rounds in was seeing ejector marks on the brass which I was surprised about and then it pierced a primer. Sheesh I thought - thats unexpected. Pulled bullets and loaded up 30 more at 27.5gr and 28.0 grain. Just in case, double checked firing pin protrusion (.058) which is normal AFAIK.

Went back out and fired the 28 grains with no issues but still ejector shine (running 2825 over a chrono) and then the 27.5's and whack, pierced another primer and ruined my trigger in the process, grumble grumble.

Its hard to believe that running 2 grains under what others use for fire forming and 3 grains under a "common" load in the BRA formed should be piercing primers. This is a brand new lot of H4895 so no experience if its hot or not, just what you see above. Primers are CCI 450's that I'm using in a 6 creed without issue, so I'm hesitant to blame the primers as being soft.

Looking for suggestions on if this is really just a load issue and I need to run even less like 26 grains for forming? But I can't imagine running anywhere close to 30.5 (just a commonly used amount) if the unformed cases are showing pressure this soon. Could the headspace or something about the chamber be off/problematic?

Any advice appreciated!

 

[Alex Wheeler]

.011" headspace is way too much. Throw those cases away. Jamming .010" will not hold them back. Set that barrel back .013-.014" to get a snug fit. I have had ejector marks at 28.5 grains fireforming, I use 28 grains. So much of this depends on the bore volume and powder lot as well as bullet. Fire form with a load that does not give pressure signs, you will need to find the right load for your setup. Piercing primers is not necessarily a pressure sign. Without knowing what action, pin diameter and spring I dont know what to recommend.

 

[Highpower-FClass]

What bullet are you using and what is the COAL when jammed 10 into the lands?

 

[dnellans]

Thanks for the replies guys. I've taken a few more questions offline to Alex before responding here.

Bullet is 105 RDF leftovers I've got, I'll have to check COAL - I was more interested in the jam than the COAL for obvious reasons.

 

[dogdude]

I just fireformed 85 rnds with 28.5 H4895 and BR-4's in a Brux @ 2850, Sierra 107's..no problems.

 

[Thud]

What Alex say's.

 

[carlsbad]

post a picture of your primers.

 

[CaptainMal]

Fireform like you do Dashers. With that much headspace you would need a tight jam over .030" or a false shoulder in the neck. The size properly for that chamber or toss the mess and set that barrel back so it headspace properly at the base of the neck.

Guessing Alex filled you in on the headspace goof-up.

 

[dnellans]

Yup - sounds like (without actually saying names) that a piece of equipment I used to headspace was off by about .008 long rather than the typical .004 short and without a 6br guage to double check against I didn't think to shim the cases to check until actually shooting them... I'll be dropping a thread and rechambering rather than trying to noodle around and make this work.

I appreciate all the input guys, exactly what I was looking for

 

[Stan Taylor]

Yes I agree with most of what people have said including Alex you didn't do a true bra by going too deep but if you would have used a 205 Federal and stuck the bullet 10 thousands in the lands you probably wouldn't have even made this post.

 

[mikeeg02]

Something else people forget when giving load data........... neck tension.

I've shot a lot of, and suggested 29-29.6 grains h4895 with lapua brass. But I also don't use any neck tension. (And forget that others do) You can quickly push yourself over safe forming load by using a lot of neck tension. A friend of mine who used my reamer uses a lot of neck tension. He blew the primers out. I know where his barrel came from so I know it was a crush fit.

If you start getting ejector swipes, or are blowing primers STOP. Pull the bullets. Find out what your problem is.

If you are confident in your headspace gauge readings, you may have a short lot of brass. I have had one lot myself that fell a little short. Jamming the bullet will help, providing you are using a lot of neck tension(which it sounds like you might be). It will have to overcome the pressure from your ejector spring.

All in all, I'd pull the bullets, and back off on the powder. Based on the fact the virgin cases are a little short, it could be causing the the primer blowouts. But the ejector swipes are suggesting you should probably back off some.

Hope that helps.

 

[Jeffrey Tooker]

Fireform like you do Dashers. With that much headspace you would need a tight jam over .030" or a false shoulder in the neck. The size properly for that chamber or toss the mess and set that barrel back so it headspace properly at the base of the neck.

Guessing Alex filled you in on the headspace goof-up.

Per Alex in an earlier thread on FF 6 BRA. The neck shoulder junction on 6 BRA is .004" shorter than the neck shoulder junction on 6 BR. A properly head spaced barrel will hold the cartridge properly to FF for 6 BRA. I am FFing 6 BRA brass tomorrow. It should work as I fired a primer only, no bullet piece of 6 BR brass in my 6 BRA. It fired properly.

Jeffrey

 

[Coolcarl]

I fireformed 480 dasher cases using the false shoulder method with Federal 205m primers. Never had a primer issue and only 2 out of 480 blew a hole in the shoulder. All the measurement stuff is still a bit above my knowledge, but .011 headspace sounds too high. I've had issues with CCI 450's being maybe too hard or possibly my firing pin spring being a little old and light. Just thoughts, Goid luck!

 

[DJSBRS]

I hydro-form .003 short on a 6BR go gauge. They fit Alex Wheeler's chamber just right.


DJ
DJ's Brass Service
djsbrass.com
205-461-4680

 

[dnellans]

Thanks for the replies everyone. I've come to the conclusion that thinking that I was being a smart guy and just having a dedicated go made for the BRA is the source of my issues. Lets just say that if I'm .003-.004 short on the BR go, it is -not- equiv to what my dedicated BRA gauge is. I'll be doing a little machining accordingly....

 

[NorCalMikie]

First thought on ANY new case/round? Pierced primers? (forget the firing pin bushing thing )
Cases too short, (headsapce) When firing pin hits primer, case moves forward in chamber, round fires and primer tries to back out and gets pushed back into pocket and gets pierced. Just as easy as that. Once brass if fire formed, that problem is gone.

 

[DJSBRS]

It is very easy to get confused on the the specs for the 6 BR vs 6BRA. Simply put as I ascertain the reamer prints from JGS, the case wall on the 6 BR 30º is moved forward by .048 and the the neck shoulder junction is shortened by .004 and thus moving the shoulder angle back to 40º to form the 6 BRA 40º . The actual head space is .004 shorter on the 6-BRA 40º than the 6-BR 30º.

DJ
DJ's Brass Service
djsbrass.com
205-461-4680

 

[dnellans]

Getting a fair number of responses and PM's on this. Thanks everyone for the help, I do believe I've got it diagnosed at this point.

Here is what Manson has to say on the topic just as another reference point (which agrees with consensus on chambering .004 short of the parent case go): https://mansonreamers.files.wordpress.com/2015/06/ackley_gaging1.pdf