Are you still running through this process or was a solution found?I have exhausted all attempts at trying to solve the soot on shoulder issue. I am getting the soot on Alpha 6BRA brass as well as on my 284 Winchester using Lapua 284W brass. I typically use a .268 neck on my 6mm’s and a .313 on my 7mm’s and never experienced this.
The problem exists on my NO turn chambers and what is odd is that the virgin brass seals just fine. The soot appears after resizing on the second firing.
Most would say:
1-Your running low pressure but not in my case. My 6bra is running 2900-2920 using Varget/h4895 and Sierra 107 or Berger 108’s. My 284w w a 28” barrel is pushing Berger 180’s 2760-2790 using h4350 and h4831sc.
2- You have excessive headspace and are bumping the shoulders too much…. Well I only bump .002-.003 as measured with firing pin removed and to allow the bolt to drop closed freely. I did try sizing .005-.001 but I got some resistance on closure and on opening of the bolt and the soot was still present on the shoulder.
3- You need to anneal more aggressively….. I got my 6bra and 284w brass glowing red at the neck to perform the test and the soot still there.
4- Your die isn’t compatible with your chamber. For the 6bra I used a Harrell’s and a whidden die with the same results. With the 284, the body shoulder junction on virgin brass measures .473”, fired brass is .478” and resized is .476”.
5- You have insufficient neck tension. I used an arbor press with seating pressure gauge. Usually 20-40psi is where I am at with .002 neck tension. I also tried in the 40-60psi range and some of my 284 was registering over 90psi and none of this made a difference.
6- Your chamber neck is over sized. My no turn 6bra is a .274 and my 284 is a .319. My loaded 6bra is .269 and loaded 284 is .314. Virgin brass does not exhibit the soot on the shoulder.
7- I did test some of my brass that was neck turned for a .268 chamber. This brass was .265 loaded and it did seal when I fired it in the .274 no turn chamber. The whole point of the No turn is to not have to neck turn!
As for accuracy at 600 yards both are performing with excellent results in an fclass setting(2.5”-3.4” 15 shot groups and vertical is in the 1”-2.4” range). My chrono numbers with the 284 are nice and low. The 6bra has some higher ES/SD but it’s shooting very good. My .268 6bra had some very tight chrono numbers but it did not shoot any better than my NO turn. For 600 yds I am not too worried about what the chrono is telling me.
Any suggestions or something I might be overlooking?
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Shooting a Proof pre-fit 6.5, Staball 44.1, 140g pills, Lapua LRP, Fed210....hilarious reading your first post it's literally me. Fire forming has been the only time my shoulders weren't messy(no FL resizing done on virgin brass). After 1st full length poof there ya go. Most accurate rifle I've ever owned and at ELR doesn't make a hill of beans. Checked velo and SD/ES at 2500 rounds and same as after barrel sped up at around 200 rounds.
At this point I just look at it as an annoyance, but would be fun to eventually find out the culprit. Have my next Proof back up ready to go on any day when this one says no mas. So interested to see if it's possibly something just with this barrel and my replacement takes care or it. Either way not inclined to burn too many brain cells or time over it given how well it shoots.
Thanks for your input.