Is powder residue on should & neck a safety issue?

[SakoShooterSD]

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.

 

[justgoto]

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.

 

[Gene]

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.

 

[boomtube]

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

No.

 

[SakoShooterSD]

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.

 

[str8shoot]

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.

 

[Nalgi]

That looks like my ammo

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

Its not a beauty contest

 

[Jinx-)]

do you remove oil from the chamber and bolt face before shooting your rifle?

 

[justgoto]

a picture of the whole case, for three pieces

I just wanted to see if the cases had signs of case head separation, since the shoulders looked so worked.

This is what I was looking for, (something I don't see on your cases.)

The dark band in the light area is the point where the separation is taking place on this 30-06 case. I used a bent paper clip to feel the inside of the case to confirm the condition.

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?

I have never used those measuring devices; but I do think the adjustments made had shortened the case to below your chamber's specs.

 

[Mikecr]

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?

This can be an issue(among many) with FL sizing, depending on your cartridge design, chamber, die match, and load. As the die works down the case body and sizes the lower body(more than anywhere else), it's squishing brass upward(toward least resistance), back into the shoulders & neck, defeating any bump. You might also notice the brass growning in OAL, donuts forming, and frequent need for trimming.
IMO, this is a point where you've gone too far for THAT die & YOUR chamber formed brass.
You shouldn't have to work brass hard for a standard bump.

 

[SakoShooterSD]

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.

Str8shoot, I think you may be correct!
Of course, the powder is just part of the question in this "multi-variate" problem.

Yes, i think 68.9 gr is below the max recommended charge for Retumbo (though it is not listed specifically for 150 gr bullets in my Barnes manual), . . . but seems to produce very good velocities, very consistently at 2964 fps (+/- 9). As such, it is a very efficient load, but . . . may be part of the reason I'm seeing the powder fouling on the shoulder and neck . . . especially if these cases have been overworked by 3 cycles of FL resizing with .008" of shoulder movement. I like the Retumbo because it seems to have a bigger sweet spot, in terms of consistent performance in the face of changing temperature.

I have tried higher charges of Retumbo, up to 70.5 gr with 150 gr bullets (and up to 73 gr with 140 gr bullets) . . . but I do not know whether the same shoulder fouling occurred. I will have to look at that again.

I also have IMR 4831 powder on hand, which has also been very good in this gun, and seems to produce higher pressures. So, I think I will try that again for comparison, though the recoil seems to go up while the velocity goes down. (Not as efficient a load.)

I have not tried the H1000. I was planning on trying some VIT N560, but everybody seems to be out of it at the moment. I think it would produce higher pressures, too.

If I can get this powder fouling to go away, I'd be happy to stick with the Retumbo,
so I'll try getting these dies set up to produce just 0.001" of shoulder bump, and I may try annealing some cases, too. I hope this "problem" will go away by getting my dies set up, and reducing the work hardening on the cases.

Naigi, I don't really care what the cases look like . . . so long as they look like they are still in one piece (as opposed to a short piece sitting on the shooting bench, and a longer piece wedged in my chamber). My original question still stands: Is powder residue on the shoulder & neck a safety issue?

I don't have a good feel for when one is getting close to case head separation, though I know a guy who lost a good gun (35-338 wildcat) to it. I don't want that to happen on my 7mm Rem Mag, which I just sunk over $3k into rebuilding.

Jinx . . . I do now! ;-)

Justgoto, thanks for the picture! Know I know a little more about what to look for.

Mikecr, thanks for the note. I think you're right, the brass was getting worked beyond what was necessary for minimum bump, though I need to go back and try to sort out which head space measurements came from which die adjustments. (I may need to just start over, and so am trying to get a press set up here at my house so I can try adjusting the die and making more measurements. I may need to go get more brass and start over, too . . . though everyone seems to be out of Nosler brass for 7mm Rem Mag. I would like to try to stick with the same brand of brass, just to eliminate one more variable, though I suppose I could try another.)

Thanks for all the input, guys!

 

[Reloader222]

I would also say that it is insufficient pressure or that the shoulders had been bumpted back too much. Look at the setup of your dies. Don't push the shoulder back more than 0.001-0.002".

Secondly, if you have a rifle with a long free bore and you seat the bullets too far out, it mean that the pressure is too low in the case to push forward the shoulders. By seating the bullet deaper it would take longer for the bullet to leave the case and thus pushing the shoulder forward before the bullet leave the case. If the bullet is seated too far out, the pressure is not enough to push the shoulders forward and therefor the gasses escape and burn up to the shoulder.

The grouping suggest that there is nothing else faulty with the load.

 

[SakoShooterSD]

I would also say that it is insufficient pressure or that the shoulders had been bumpted back too much. Look at the setup of your dies. Don't push the shoulder back more than 0.001-0.002".

Secondly, if you have a rifle with a long free bore and you seat the bullets too far out, it mean that the pressure is too low in the case to push forward the shoulders. By seating the bullet deaper it would take longer for the bullet to leave the case and thus pushing the shoulder forward before the bullet leave the case. If the bullet is seated too far out, the pressure is not enough to push the shoulders forward and therefor the gasses escape and burn up to the shoulder.

The grouping suggest that there is nothing else faulty with the load.

Reloader222, thanks.
I had not thought about the bullet seating depth, but it makes good sense. I have these bullets seated for maximum recommended COAL of about 3.290", which seemed to produce slightly better groups than 0.015 and 0.030" shorter COAL. I don't yet know how far off the lands that puts these TTSX bullets, but I'm working on measuring that now . . .

My bullet seating depth measurement tool (part of the the RCBS "precision mic" kit) tells me that my chamber measures 0.020". When I use the same setup to measure one of these loaded cartridges, I get 0.008", . . . so, looking at the difference between those two measurements, I would say these cartridges have the bullet seated 0.012" off the lands. I would like to keep it around 0.010 or under if I can. (I'm a bit superstitious about guns that shoot better when the bullet has to "jump the gap". That makes little sense to me . . . though I am a neophyte at this game.)

When I put a micrometer on a bullet, it measures approximately 1.43" long (including the plastic tip), . . . and I measure about 0.82" protruding beyond the neck of the case for these loads . . . so there is about 0.6" of bullet length seated. (Base of the bullet actually sitting almost 1/4" below the shoulder). That seems like it would be sufficient, but . . . who knows?

 

[CRNA]

I have recently been hand loading for my 7mmRM. I always get powder burns/residue on the necks, but never on the shoulder like yours. I have been using H1000 exclusively. My load is 70.5g of powder pushing 168g SMKs. I use Winchester brass and Fed 215s. I am just learning specifics of reloading, but form what I have learned, it sounds like the gas is escaping around the neck (which I think is normal). The problem is the gas shouldn't make it down to the shoulder because the shoulder should expand and seal off those gases inside the chamber at the time of detonation. That may not be a whole lot of help only to say that my 7mag doesn't get the gas all the way down the shoulder. Good luck.