Powder residue on cases bad

[Matt_3479]

Wondering what causes large amounts of powder residue on case necks and body. My 6mm creed, using alpha brass, 42gr of h-4350 pushing the 105 hybrids at 3150fps leaves an insane amount residue on the case. Someone mentioned it could be due to over trimmed brass which makes sense. If that’s the case, does that mean I have to wait till the brass stretch’s back, or is it garbage?

 

[Murray Brook]

Any time I have had this happen to a case of mine it was due to too light a load and the chamber wasn't sealed well enough. Also happened to me when I had not enough bullet in the case ( chasing the lands) to properly seal the chamber. I don't believe it is dangerous but could collapse the case. JME

 

[Matt_3479]

Any time I have had this happen to a case of mine it was due to too light a load and the chamber wasn't sealed well enough. Also happened to me when I had not enough bullet in the case ( chasing the lands) to properly seal the chamber. I don't believe it is dangerous but could collapse the case. JME

I’ve heard of this with light loads but 105 hybrids travelling at 3150 doesn’t sound light to me. I chrono’d it today.
The bullet in the case thing I’ve never heard of before! Might look into that a bit, but I believe I’m at the perfect depth (just above shoulder neck junctions

what do you mean on collapse the case?

 

[eric32]

1- It's a headspace issue, your are bumping back way too much.

2- your brass is neck is hardened and won't seal.

BUT I think it's 1# check your base to shoulder measurement of a fired and sized case.

 

[Tommie]

Agreed: Looks like the case isn’t sealing the chamber.
Agreed: Your load certainly doesn’t sound light.

Watching this thread.

 

[Murray Brook]

When the gas pressure gets past the case neck before the chamber is sealed the case can collapse or end up with shoulder dents some what like when too much lube is used in resizing only worse. I had this happen in my 7/08 with the 168 Sierra MK. To keep my OAL at .020 off with a very worn throat I had to load very long resulting in smoked cases and big dents. JME

 

[Matt_3479]

When the gas pressure gets past the case neck before the chamber is sealed the case can collapse or end up with shoulder dents some what like when too much lube is used in resizing only worse. I had this happen in my 7/08 with the 168 Sierra MK. To keep my OAL at .020 off with a very worn throat I had to load very long resulting in smoked cases and big dents. JME

that’s interesting! I’ll keep an eye out but haven’t had this happen yet!!

1- It's a headspace issue, your are bumping back way too much.

2- your brass is neck is hardened and won't seal.

BUT I think it's 1# check your base to shoulder measurement of a fired and sized case.

I just double checked 5 fired cases at 1.5315-1.5325 thou is what I was getting. I check 15 sized cases and got an average of 1.530. The smallest being only 1 case at 1.5285 and the longest being 1.5305.

how would I know if it is neck hardened? Meaning to fix this, I need to anneal more often? That something I’ll look into, but it’s been happening since the second firing on these cases?

that is what I was telling a local f-class shooter at my club today and he mentioned if I had a slightly long chamber and I over trimmed a bit it could cause a bad seal, or so he thought.

 

[mikecr]

That is true about over trimming,, it allows gas backflow around necks -to shoulders (a thin film).
But you have something else going on beyond that.
Something big & bad

 

[eric32]

Who did the chamber on the barrel?

Are the pictures 3 sides of the same piece of brass?

 

[Matt_3479]

Who did the chamber on the barrel?

Are the pictures 3 sides of the same piece of brass?

That is 3 separate pieces of brass but I have 50
More just like it!

an extremely reputable smith in Canada.

 

[Matt_3479]

That is true about over trimming,, it allows gas backflow around necks -to shoulders (a thin film).
But you have something else going on beyond that.
Something big & bad

In that case it generally doesn’t go past the neck/shoulder area so you wouldn’t think my brass is too short causing it to blow back all
Over the cases

 

[eric32]

Do the same soot marks appear on all pieces of brass. Or does each case have a different soot pattern.

Also what neck tension are you running?

 

[Matt_3479]

Do the same soot marks appear on all pieces of brass. Or does each case have a different soot pattern.

Also what neck tension are you running?

I can look again but yes it appeared on all the brass, and if I recall it wasn’t a specific pattern.

.002 thou neck tension in my redding die

 

[eric32]

If all the soot patterns are the same. Set the cases on a table headstamp down and make sure they aren't crooked get like 5 or so and line them up.

This will point to extensive runout in your chamber

 

[Matt_3479]

If all the soot patterns are the same. Set the cases on a table headstamp down and make sure they aren't crooked get like 5 or so and line them up.

This will point to extensive runout in your chamber

when you say crooked, like the actual piece of brass may be slightly leaning towards one side over the other from perfect dead center(plumb line). When you say extensive runout, that’s talking like an oversized chamber?

I’m just trying to get all my ducks in a row on this one as I’ve never experienced soot like this on anything I’ve owned, or loaded for. The rifle shoots well but definitely not my best shooter. The excessive soot bothers me ans makes me wonder
If something I did messed it up (possibly over trimming or not enough annealing) or if something from the smith messed up.

 

[Fred B.]

Looks like brass out of an AR that is not tuned correctly.

 

[Matt_3479]

Looks like brass out of an AR that is not tuned correctly.

thats what I thought when I first saw them. I load for 6-8 rifles currently. And use the same steps on all of them. I’ve never experienced this on anything other then this particular rifle.

 

[eric32]

Yes if the case are leaning to one side or the other relative to the others. This would indicate that the chamber is either oversized or crooked relative to the bore axis.

So if all the cases are straight (they all stand straight up and down whilst on the case head)

Then you can rule out a bad chamber.

To me if this is the frist time you are seeing this sort of results and this is NOT an AR15 with a gassing issue.

Then my train of thought is to have the chamber inspected and tested for runout along the chamber walls.

If you find soot marks are some what repeated along several pieces of brass that would tell what part of the chamber is sealing and what isnt.

My assessment is that the brass is not able to stretch to seal the chamber. Due to the barrel chamber being oversized and not concentric with the bore.

 

[243winxb]

Increase neck tension/Bullet hold. Start pressure is low. Bullet moving to soon. OAL to long, trying to get near rifling. Little bullet shank in contact with the case neck.

A longer the normal free bore/throat can be an issue too.

OR- This.

 

[Matt_3479]

Yes if the case are leaning to one side or the other relative to the others. This would indicate that the chamber is either oversized or crooked relative to the bore axis.

So if all the cases are straight (they all stand straight up and down whilst on the case head)

Then you can rule out a bad chamber.

To me if this is the frist time you are seeing this sort of results and this is NOT an AR15 with a gassing issue.

Then my train of thought is to have the chamber inspected and tested for runout along the chamber walls.

If you find soot marks are some what repeated along several pieces of brass that would tell what part of the chamber is sealing and what isnt.

My assessment is that the brass is not able to stretch to seal the chamber. Due to the barrel chamber being oversized and not concentric with the bore.

hmm okay I will look for this today!! I never thought of that even being possible due to the reputation of these smiths but will definitely go about to look for it. I will also inspect each piece of brass to see if the pattern holds true or are at comeplte random. From what I recall it was just random.

rifle isn’t an ar. Kelbly atlas tac, bartlein bbl, mpa chassis.

im thinking my first thing I’ll do is buy a box of factory ammo. If they also come out soot covered then I know it’s both something I did to my brass during prepping and loading. If they do, I might toss this brass and start fresh with a new batch and be more cautious.