Marks on Brass...w/Factory Loads?

[Phil3]

I was shooting some Blackhills FMJ 55 grain ammo (Winchester brass) in my AR15 and noticed that upon inspection of the brass, their are shiny marks from the ejector plunger and the straightline from the extractor. I had come to understand such marks may be indicative of excessive pressure. But on factory ammo? My own handloads, which I am just starting with low loads, show no such signs. The factory brass shows no flattened primers, brass stretching, or any other problem. Is some marking of brass normal in an AR-15?

Phil

[high_revs]

take a picture phil and post. i use blackhills also when i'm feeling a little spendy (the heavier gr). i don't see such markings on any of my ar15 brass.

[afrancke]

I've had similar marks (and similar confusion) with respect to extractor swipes on factory-loaded ammo. After much googling about, I found various theories including insufficient lock time after firing but before extraction, which called for a heavier buffer, less gas or similar to change the timing of extraction. I haven't yet tried tuning anything, however.

Agree with high_revs: need pics to say anything conclusive. Also, include on barrel length and buffer type.

[Phil3]

OK, here are a few pics. Barrel is 22" long, with gas port in standard place. Barrel is Krieger. JP Rifles standard gas block (not adjustable). Buffer and spring are standard Rock River Arms issue. Black lines on brass are from a Sharpie so I can recover my brass when ejected. No signs of brass stretching of primer flattening. Black lines on case end appear to be where extractor edge was against case. - Phil


Middle row, two on far right. See shiny marks.


Middle row, far right again. See impression of extractor edge that is in face of bolt.


Bottom row, far left hand cartridge. Looks like ejector smear at 8 o'clock and extractor edge at 2 o'clock.

[Ferrum]

I occasionally have this issue in my AR's, usually in .308, not .223. Trouble shooting mine, it turned out to be excessive pressure. To the point it was blowing out some primers.

If you aren't reloading, I'd by a couple boxes of different manufactures .223 and see which works the best without causing issues.

Somewhere here I posted pictures of mine having the same problem...

[damndave]

Those look like extractor marks from hot loads. I would be careful if planning on reloading those brass again.

[Phil3]

How can these be "hot loads" if standard Blackhills 55 grain FMJ ammo?

Phil

[ExtremeX]

I found various theories including insufficient lock time after firing but before extraction, which called for a heavier buffer, less gas or similar to change the timing of extraction. I haven't yet tried tuning anything, however.

I was thinking this too... maybe play with buffer weights or get an adjustable gas block and see if it helps the problem.

[ExtremeX]

How can these be "hot loads" if standard Blackhills 55 grain FMJ ammo?

Phil

[milw50717]

The OP mentioned Winchester brass, but the headstamp looks to be WCC NATO, so it is also Western Cartridge Company 5.56 remanufactured and not factory new.

http://en.wikipedia.org/wiki/Headstamp

[Phil3]

The ammo is Black Hills ammo. It is "red box", in 223 Remington. 55 grain Full Meta Jacket. The tops of the cases are discolored so I presume the brass is not new?

I should mention a few other things that may be relevant, but did not think about at the time.

- I never really noticed the typical "boing" from the recoil buffer spring I usually hear, regardless of whether it was the factory ammo or my lightly loaded hand loads. Maybe I am used to the boing or perhaps there really was a change and that is symptomatic of a related problem.

- Virtually none of my hand loads showed the kinds of marks the Blackhills ammo showed. My hottest handloads were 22.8g Vhitavouri N133 and 23.0g of Hodgdon H322. The Blackhills was not particularly accurate.

- I fired the Blackhills ammo first while at the range, with no cycling problems, but short stroking began to happen with more rounds fired of my hand loaded ammo, getting worse as the day wore on, despite using increasingly hotter loads. I think the bolt may have been too dry, but not sure.

Phil

[Phil3]

The OP mentioned Winchester brass, but the headstamp looks to be WCC NATO, so it is also Western Cartridge Company 5.56 remanufactured and not factory new.

http://en.wikipedia.org/wiki/Headstamp

My bad. I thought for some reason was "WCC". If these are 5.56 cases, could that explain the higher pressure? Even if the box is marked 223 Remington?

Phil

[Phil3]

I was thinking this too... maybe play with buffer weights or get an adjustable gas block and see if it helps the problem.

I guess I am a little puzzled as to why this is necessary. The rifle is standard in every way that would matter in lock time, gas pressure, etc. It uses a Young Manufacturing chrome bolt and carrier, 22" long Krieger barrel with a rifle length gas system, Krieger barrel extension, standard gas block, standard Brownell's gas tube, and run of the mill Rock River Arms buffer and spring. The barrel according to Krieger is chambered in 223 Remington and not for 5.56. I only use 223 Remington.

Phil

[the86d]

I picked up some brass from a guy who was shooing 5.56 NATO at the range and he mentioned that his brand screwed up brass and that I wouldn't want his, and he was right. The necks had split-nicks in it and the same stuff had similar... I want to say claw marks that looked like what you have pictured, the head wouldn't fit in my case gauge after sizing, and while sizing I had a few stick in the shell-plate. Nick/claw mark in each case head made the beginnings of a rim. I cannot remember what he said the brand of his rifle was...

[Phil3]

Hmmm...., this is interesting and might explain some things.

http://www.savageshooters.com/showth...ition-(Red-Box)

Phil