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Is powder residue on should & neck a safety issue?

 
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  #1  
Old 05-15-2011, 11:09 PM
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Join Date: May 2011
Posts: 17
Is powder residue on should & neck a safety issue?

I would love to get some feedback on whether or not I am running into a safety issue (for the gun or the shooter) when I observe a black residue (burnt powder?) on the neck and shoulder of my 7mm Rem Mag cases upon extraction. (pictures attached).

I noticed this on some rounds fired Friday at the range with the latest loads I've been developing with my Dad. I fired 6 rounds total on Friday.
Some show little or no residue. Some show significant residue, down to just above the base of the shoulder.

After the first two shots, the group turned out nice and tight: 0.35" for four shots, at 100yds. So I think the accuracy is good enough for hunting.

But, is this residue on the shoulder a problem that I need to worry about?
Is it dangerous?
(Will it lead to damage to the gun or shooter?)

These latest loads were done with the following recipe:
Nosler brass, full-length resized in RCBS dies. (This was the third or fourth firing.)
68.9 gr of Retumbo powder.
150 gr Barnes TTSX bullet.
CCI 250 LRM primers.
COAL 3.290".

The first rounds fired did not have any mark, but I think that was because there was some leftover lube in the chamber from the previous gun cleaning. This may have either provided prophylactic protection, or may have changed the pressure in the chamber, and the reaction of the brass. I'm not sure, but I do know the cases had lube on them after extraction. (Yes, I should have run a dry patch through the gun before firing. Next time I will.)

Any input would be welcome.
Thanks.
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Is powder residue on should & neck a safety issue?-img_1055.jpg  
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  #2  
Old 05-16-2011, 03:12 AM
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Location: Carrollton, Ohio
Posts: 573
Re: Is powder residue on should & neck a safety issue?

I regularly get the powder residue on my case neck, never heavy like you have there and never passed the neck.

I would guess that you have full length sized the case too short. That would give you a young case life and possibly case head separation in just a few firings. I sure would like to see the whole case.

I neck size only, unless I have insertion/extraction problems.
But if you are set on using the full length sizer, I would set-up the full length die to where it just bumped the shoulder back a smidgen.
When I do use my full length sizer I take one case of the batch I am going to size, and using the flame of a candle I put carbon on the shoulder. Then I set the die as to not touch the shoulder with a full stroke of the press. Then I tighten the die down 1/8 turn, run the case through the press; until I see that the carbon has been touched.
Then I re-size the rest of the cases at that setting.
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Old 05-16-2011, 06:37 AM
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Re: Is powder residue on should & neck a safety issue?

That is a good answer.

You are probably sizing the case back too far. Does this happen when you neck size only?? It appears to be powder blow back, caused by failure to seal the neck/shoulder area properly. If so, you are also creating excess headspace, and that could be dangerous. I keep necks clean by twisting them in a wad of 0000 steel wool.

If neck sizing only does not solve this problem, have the headspace checked by your smith.
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Old 05-16-2011, 07:21 AM
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Re: Is powder residue on should & neck a safety issue?

"Is powder residue on should & neck a safety issue? "

No.
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  #5  
Old 05-16-2011, 02:21 PM
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Join Date: May 2011
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Re: Is powder residue on should & neck a safety issue?

Quote:
Originally Posted by justgoto View Post

I would guess that you have full length sized the case too short. That would give you a young case life and possibly case head separation in just a few firings. I sure would like to see the whole case.

I neck size only, unless I have insertion/extraction problems.
But if you are set on using the full length sizer, I would set-up the full length die to where it just bumped the shoulder back a smidgen.
Thanks for the feedback, Justgoto, Gene and Boomtube. I really appreciate your thoughts.

So, . . . here is some of the rest of the story . . .
I bought three other sets of dies:
Neck only sizing die set from Forster
Neck only sizing die set from Lee
Full length sizing dies from Forster

. . . and was working with my Dad, remotely (he had all the reloading equipment) to try to get the FL dies set up for "minimum shoulder bump", very similar to what you described. I wanted to bump the should .001 or .002 (as opposed to neck-only) since these loads are for hunting. We have a head space measurement tool from RCBS, and were making measurements as the die set up was adjusted similar to your recommendation. We got it set so that it would do the full neck, and just touch the shoulder (based on permanent marker ink being disturbed), but when we tried to go a little further, there was no measurable change in headspace measurement. So we tried to keep cranking down on the die adjustment. After much much more than 1/8 of a turn (1/12, 1/8, 1/4, 1/2, whole turn, etc. . .) there was still no measurable change in head space. (!)

At that point, we were both scratching our heads, so Dad brought me a spare press, along with most of the equipment I would need to do some reloading, and I am going to try to reproduce the same results, or see if I can't figure out how to get the minimum shoulder bump I'm looking for.

In the meantime, Dad did some more reloads with the RCBS FL dies, which produced the latest results. Great groups on the target, but funny powder marks on the brass. (It may be that there were similar powder marks on the brass in previous reloads. I didn't pay that much attention to them, but I am seeing some evidence of it on older brass.)

At this point, I'm tempted to
1. try using my IMR 4831 recipe, which may produce higher pressures,
2. try annealing the brass (though I don't yet have the set up to do it) and use the Retumbo recipe again,
3. try using the neck-only sizing die . . . though this may not fix the issue if the brass has already been work hardened from too many cycles through the FL dies.
I suppose I should try all three.

Has anybody had a similar experience where the measured head space didn't seem to change, even as the dies were adjusted down more and more?
Seems bizarre to me. Maybe the dies are designed to go only so far, to stay within SAAMI specs?

Gene, here is a picture of the whole case, for three pieces.
I'm not sure if the resolution will be fine enough for you to see what you're looking for.
Notice that two of the pieces have powder on the necks, and a little area on the shoulder, while one piece has powder covering almost the whole area of the shoulder.
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Is powder residue on should & neck a safety issue?-img_1069.jpg  
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  #6  
Old 05-16-2011, 09:24 PM
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Join Date: Jul 2010
Location: Bozeman, MT
Posts: 151
Re: Is powder residue on should & neck a safety issue?

I was getting powder residue on a newly rebuilt 7 mag. It turned out my chamber was a little rough. Yours doesn't seem to show the signs of a rough chamber. I bet it is the powder. A faster powder will expand that case faster (before the burning powder comes up the case neck). I think that load actually needs a little more pressure.
Retumbo is a pretty slow powder for the 7 mag. It works well for the heavy bullets. I prefer h-1000 to retumbo and I shoot mostly 160-180s in my 7mags. If I were gonna try some 150s I'd use H-4831, it seems to work pretty well with most weights.
Hodgdon lists a max load of 72.5 gr Retumbo with a 150 partition. I really think you are under pressure with that load, have you tried higher charges of Retumbo? Do you haven't any other powders on hand to try?


As far as bumping the shoulder, I actually had to grind down the bottom of my die to be able to bump my shoulder just .002. I removed enough material that my shell holder wouldn't touch the die when it is set up correctly.
Hope any of this helps.
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  #7  
Old 05-16-2011, 10:19 PM
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Join Date: Oct 2010
Location: UT
Posts: 38
That looks like my ammo

If you are getting good groups, who cares what the case looks like?

Its not a beauty contest
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