I’m not a reloader yet so haven’t paid much attention to my spent casings but have noticed lately that there is a slight bulge toward the rim. Unfortunately I don’t have a good picture of mine yet but found a picture online to illustrate what I’m concerned about.
Looking at range brass from other ARs, most of it has less bulge than mine but my brass is not as bad as the picture below. (Sorry, I’m trying to find a camera with a good enough macro lens to add a picture of my brass.)
I understand that some bulge is normal and some brass exhibits it more than other brands. Right now I’ve noticed this with PMC .223 55gr FMJ but need to try other brands and 5.56 as well.
Besides an improper chamber I understand the timing of the bolt release can cause this - extraction can start before gas pressure drops enough - and a heavier bolt carrier, buffer or spring can improve the timing.
I have an ArmaLite midlength upper with a BCM M4 Gen 2 Stock Kit and H-buffer.
Quentin,
Some cartridge cases bulge worse than others depending on quality.For instance,S&B brass is very light/thin walled and bulge badly.Ive seen this with the S&B .223 Rem and 7.92x57js brass,in that the stretch/bulge in the webb is enough to cause concerns when resized.Same could be said of some of the Federal .223 Rem brass and nickel plated brass cartridge cases Ive had.I have no experience with the PMC.
Remember on the AR the cartridge case head up into the webb is exposed within the bolt and then the radiused area of the breech into the chamber.So there will be some bulge evident in the cartridge cases depending on the dimensions of the bolt face,chamber/headspace,quality of the brass and the pressure of the ammo.
I’d try some higher quality ammo and see if there is any difference.
If your real concerned contact Tim at Armalite and run it past him.If there are any concerns he pass you on to the gunsmith they will issue a RMA#.
ETA
Here is some good info to have on hand as well regarding headspace. http://www.ar15barrels.com/data/headspace.pdf
Also,in the drawing you can get an idea of what Im talking about in regards to the bolt and breech in regards to the exposed cartridge case head/webb having little to no support from the chamber.
Thanks for the excellent information, Blankwaffe! And again thanks for help you’ve given in the past, very informed and helpful.
I wish I had saved more brass over the last year and will from now on - now that I’m learning it’s an excellent barometer of proper function.
I believe the rifle is safe and it’s functioned perfectly since I put the complete upper on a lower I assembled last Oct. so it looks like the next step is to try better ammo. PMC seems to be all right but there are much better choices. I will get pictures and contact Tim. Since the upper showed obvious signs of test firing I would hope ArmaLite inspects the brass as part of that test before letting something unsafe go out. Of course you never know.
Quentin,
Your welcome my friend…just hope I helped more than hurt.
Maybe someone here that is more experienced than myself can relate a bit more information to the subject.
As far as your rifle and the spent cases,hard to say without seeing what you have in hand.But Im willing to bet the rifle is fine and is more than likely traced to the ammo causing your concerns.
I have a Armalite middy just like yours.Im running a H buffer with LMT M16 BCG(Colt extractor spring/insert and no o-ring) and BCM USGI action spring.Spent cases eject to 3:00-4:00 o’clock depending on ammo.Weaker ammo runs a bit later than that(specifically Wolf).
Where is your rifle tossing the PMC brass?
Thanks again Blankwaffe and you certainly helped, not hurt!
The PMC cases eject at 3:00 and so far all brands eject to 3:00-4:00 o’clock. So it sounds like our uppers are performing similarly which is good since they’re configured about the same. The main differences are that you have an M16 carrier and mine is ArmaLite’s slightly lighter AR-15 version - and I still have the extractor O-ring (I know, I know! :stop: but I’d better not change things too much right now). I hope to get out this weekend and try better rounds including some 55gr 5.56. Will update…
Interesting! I was testing several loads in a controlled study where I had two uppers… the T&E middy from BCM, and my Wylde chambered WOA middy upper.
The WOA had bad bulging similar to what you pictured when I fired several loads through it… (the hotter the load, the worse the bulge) The SAME load fired in the BCM upper had no bulge issues at all.
That’s what I’m wondering about my “so called” Wylde chamber. It looks like Glock 40 cal brass.
The beauty is I can Identify the specific chamber because I was shooting hand measured powder charges out of both. I can even tell what part of the chamber is bulging by the extractor imprint on the case rim.
Yall did catch the line in Quentin’s post that said that the cartridge case picture above is not one from his weapon,but rather one he referenced.
I say wait until he has tried some different ammo and has more details(actual pics) before going to ground.
You might want consider not setting the shoulder back so far. If you can get access to a case mic, measure your fired round and then size it to -.001 to -.002 undersized. Then you will not get the bulge and the head separation that is coming. Make sure and check those cases for stretching with a paper clip, end bend 90 deg.
My primers also are slightly flattened. I’m having computer problems right now but hope to get some good pictures of my PMC brass posted. I have a Daniel Defense M16 style BCG ordered and will test better ammo with both BCGs then and post pictures. Doubt that will help but at least I’ve needed a spare BCG so why not see what happens.
One down and dirty test I have done is press a bulged spent casing back into the ArmaLite chamber and it went in fairly easy and popped back out with a slight tap of a cleaning rod from the muzzle. I then tried it in a Bushmaster chamber and it wouldn’t seat fully with thumb pressure and took a pretty good rap with the cleaning rod to dislodge it. So no doubt that particular Bushmaster chamber is tighter than mine.
This was happening with factory ammo (Q3131a1) in my Wylde chamber. The exact same ammo (same 20 round box) did not do this in the BCM chamber.
Q3131a1 is not super hot ammo. It’s about 100 fps slower than full blown M193.
The problem is less pronounced in my hand loads, but you could still see it.
Very sorry to take so long getting pictures of the bulging I was trying to describe in this thread. The first picture in the thread was an example I found online, it was not fired from my rifle. I was unable to get a good enough macro shot of my brass until now. The following pictures of spent cases are from my rifle. I hope they illustrate what I’m concerned about. The rifle fires fine and I’m hoping this is just a slightly loose chamber.
As quoted below this is an ArmaLite midlength upper however for this test I replaced the BCG with a Daniel Defense M16 BCG. No change in the appearance of the brass. A BCM H buffer and spring were used.
Side view - From left to right:
Winchester 55gr 5.56, PMC 55gr .223, G.F.L. Fiocchi .223, G.F.L. Fiocchi .223, Federal 55gr .223, steelcase .223
Primers - From left to right: (PMC a little flattened)
Winchester 55gr 5.56, PMC 55gr .223, G.F.L. Fiocchi .223, G.F.L. Fiocchi .223
Primers - From left to right:
G.F.L. Fiocchi .223, Federal 55gr .223, steelcase .223
