I recently put the first 100 rounds through my new Colt 6920, a mix of 55 grain .223 and 5.56, and some 62 grain 5.56. Ran great, no malfunctions whatsoever, got a sub-2 inch group at 100 yds with the irons. Upon picking up the brass, I noticed on the 5.56 cases I could plainly see what position it was in on the bolt face, looks like the brass “flowed” into the ejector and extractor openings. See pic below:
This was not seen on any of the .223 brass, only the 5.56. I understand it’s a higher pressure round, just wondering if this is a sign of excessive pressure, or am I worrying about nothing?
Primer on left looks OK, can’t tell on the right, might have tried to unlock early. Looks like factory loads. Tracker is right, need to see cases from all angles. Inspect the chamber for all he mentioned, bolt face too, run a Qtip in the chamber, see if it snags, and look in there, should look perfect.
I have seen this with the Winchester USA ammo before. Did you see this with any other brand?
Yeah, I took pics from a few other angles, but that was one of the few that weren’t too blurry. This one may help:
The rifle was cleaned and lubed prior to shooting.
Chamber was dry, as far I could tell.
No primer setback evident on any of them.
The bright spots can be felt, when I run my finger over them. You can see on the pic above a bit of a chunk taken out. More evident on the 62 grains, I notice.
Recoil impulse seemed slightly sharper with the 5.56. Figured this was normal. Of course, this IS my first AR…
The sound wasn’t noticeably different from the .223 loads.
Only the 62 grains (shown) have the NATO markings. The other 5.56s were Federal and Winchester 55gr. Those show less deformation of the brass. (harder to pick up with my crappy camera.)
All of the .223 look normal.
All factory ammo.
Bolt face looks fine, as far as I can tell. Chamber looks clean and smooth.
I take it this ISN’T normal…
I see it on all of the 5.56 I’ve fired, to some extent. Worst on the NATO marked Winchesters, least on the 55 grain Federal. None at all on the .223.
Its fine that is the ejector and extractor marks. Do not worry about it unless you start loosing primers.Then I would Be.
Quib’s tutorial on EVO. http://www.weaponevolution.com/forum/showthread.php?1948-EJECTOR-EDGE-CHAMFERING-FACE-POLISHING
The cases look pretty normal for a carbine. M193 type pressures and carbine gas system, with a stock (?) buffer, will cause a little brass smearing. Not a big deal. If you want it to stop, try a heavier buffer.
Looks totally normal dude.
In general, the best indicator of pressure to use is primer flattening, or primers popping out of their cases and into the receiver.
Reloading manuals do show the primer flattening can be caused by things other than high pressure though… just an FYI, but that’s almost what all amateur reloaders use as an indicator for pressure.
Gentlemen, thanks for the answers and the link. I’ll keep shooting it as is, and keep an eye on it. I’ll probably invest in a go/no go gauge, since I’m building another and one can’t have too many tools.
I’m sure you are fine. Colt makes good stuff. I have seen similar marks on brass using winchester 5.56 (q3131a1) in new uppers that are 5.56. I don’t know for sure but I imagine that as a new upper the tollerances might be toward the tight side of spec (headspace, chamber, chrome, etc) which may add a bit to the pressure…It will probably “break in”.