Ejector Marks on Factory Loads

[6ShotsOr5?]

i have two AR10 platform rifles in two different cartridges that I noticed are making ejector marks on the cases. The only common factor I can see is the barrels were made by the same company. The ejector marks are occurring using factory loads, and several different brands and bullet weights are doing it. I have read a few threads saying ejector marks are a sign of excess pressure, but that doesn’t seem likely to be the issue for factory loads. Also I have done a lot of chrono work and my factory ammo is always within 50 fps or so of what they say on the box, usually slower because my barrels are shorter than their test barrels, so I know the rifles aren’t shooting at higher than normal velocity. I’m wondering if it could be related to the new case shoulders being a little short for the chambers so the case heads are getting slammed back against the bolt face with a little momentum when they ignite. I’m very interested to hear what others think.

Also, any thoughts on whether cases with ejector marks can be safely reused?

 

[243winxb]

The ejector marks are occurring using factory loads,

I have seen ejector marks with factory ammo in bolt actions. Really depends on how much they are raised.

Should reload ok, unless primer pockets are loose. When the bolt turns, is it shaving brass?

Low pressure starting on the right. Till primer fell out of pocket on the left.

 

[6ShotsOr5?]

I don’t know if it’s shaving brass, because I’m not sure what that looks like. If it’s a shiny spot that looks like something wiped across it, yeah I noticed some of those too, so you’re saying that is probably the ejector scraping the case head when the bolt locks up (or when it’s unlocking)?

The main thing I noticed is more of a crescent shaped mark and usually just one side, in other words it’s an ejector mark but not a full circle most of the time.

 

[243winxb]

Shaves when unlocking.

The main thing I noticed is more of a crescent shaped mark and usually just one side, in other words it’s an ejector mark but not a full circle most of the time.

I dont think theres a high pressure problem.

The hole may have sharp edges.

 

[BoydAllen]

Two things: Are your chambers bone dry, and do you have enough rounds on the barrels that they could have hard carbon in their throats? Beyond these, I would try to figure out if the throats are shorter than they should be.

 

[6ShotsOr5?]

Thank you @243winxb.

@BoydAllen, one barrel has 664 rounds and the other has 1269 rounds. I just went through a few thousand cases to grab all the ones I might want to reload, so I don’t know if they have always had these marks or it showed up more recently. I use a dry swab after cleaning the chamber, some light lubricant on the bolt lugs when I clean the bolt. The cases with the marks are cheap brass I wouldn’t want to load anyway, but both are rifles that I may reload for in the future, and I would want to fix this issue if I could before I start running any “keeper” brass. I can’t remember if I have the headspace gauges for those but if I do I will check that. Thank you.

 

[Rsadams]

A picture would help , the AR platform is hard on brass... Some powders are hard on the AR also... I would need to see it , but there's probably no problem just a slightly raised ejector hole or a sharp spot or gunk under the ejector... All are common...

 

[Delfuego]

You are over-gassed. Large frame AR's are way over gassed. You need to tune it with an adjustable gas block, heavier carrier JP Silent Capture Springs or some combination of the 3.

My 260 AR did that until I installed weights with Tubb's CWS. Unfortunately he doesn't sell them anymore.

 

[MikeMcCasland]

I'm guessing this isn't a .308 AR10? It's extremely common in 6.5 bore large-frame ARs.

You need an adjustable gas block; better yet, your next barrel you should get something with a +2/Extended-Lenght gas system.

You might also want to look into an HP type bolt too. Cratering/Flattening is also extremely common.

Lastly, if it is a 6.5 bore, most factory ammo is built for bolt guns, using slower than ideal powders for your platform. I always got better results in my AR10s with powders that were closer to the burn rate of varget.

 

[6ShotsOr5?]

Wow, a lot of great comments.

@Rsadams : pictures attached. I think you nailed it, YES, ARs are hard on brass. One brand of brass in the 6.5 photos is taking a bit more of a beating than the others, so it’s probably just softer.

@Delfuego : glad you mentioned being overgassed. I am waiting on some suppressors and I recently installed adjustable gas blocks on both these rifles and dialed back the gas so the bolt just barely locks open on an empty mag, per instructions. I didn’t check that brass because I hadn’t been looking at this issue yet. I’m going to shoot some more and see how much difference the reduced gas made, and I will follow up. What is (was) the Tubbs CWS?

@MikeMcCasland : one is an LR308 with 1269 rds on the whole Rifle and barrel, the other is a 6.5-cartridgethatshallnotbenamed with 664 rds on the barrel / rifle. The 308 has been a challenge but is running great now. The 6.5 always cycled and shot well. 18” barrel with rifle-length gas system the 308, 22” barrel with rifle gas system on the 6.5. They both have JP HP bolts in them, but oddly I couldn’t get the LR308 to run well with a high-priced fancy bolt carrier (not from JP). It just likes the cheapest DPMS bolt carrier. I think it’s because the other carrier was too heavy with the rest of the setup.

 

[243winxb]

Hormady factory ammo? I dont like the looks of primer or ejector mark. High pressure.

Or the hammer spring is wear and the ejector hole had sharp edges.

But i only have experence with M16/Mini14/AR180. So a guess on my part.

I would reload the brass , if primer pockets are ok.

I noted Sierra 223 loads were lighter for the auto loader , when compared to the bolt data. http://www.accurateshooter.com/cartridge-guides/223rem/

 

[Rsadams]

Exactly , some powders are not good for an automatic , loading hot loads for a bolt gun will be beating on a AR platform gun... Remember sometimes you have to change powders to keep pressure down.... Trying to match a factory load with hand loads speed wise can be tricky , you may have to heat it up to get the FPS with one powder which shows pressure signs , switch powder and they go away.... And yes my experience is with 5.56 M4s you want them ejecting at about the 4-4:30 area... If it's throwing them forwards you're over gassed , most are , which can be cured with heavier buffer and springs...

 

[shoot4fun]

To me, at least, the Copper Creek stamped brass looks the worst. I suspect Copper Creek is loading a bit hotter and you 6.5 gasser doesn't get along with it at all. I would give them a call and see what they have to say. Of course, all this is supposing that the brass in your pic was all factory loaded and not your reloads.

 

[Rsadams]

I would try another brand of brass or factory ammo besides Hornady , there brass is known to be soft...

 

[MikeMcCasland]

Wow, a lot of great comments.

@MikeMcCasland : one is an LR308 with 1269 rds on the whole Rifle and barrel, the other is a 6.5-cartridgethatshallnotbenamed with 664 rds on the barrel / rifle. The 308 has been a challenge but is running great now. The 6.5 always cycled and shot well. 18” barrel with rifle-length gas system the 308, 22” barrel with rifle gas system on the 6.5. They both have JP HP bolts in them, but oddly I couldn’t get the LR308 to run well with a high-priced fancy bolt carrier (not from JP). It just likes the cheapest DPMS bolt carrier. I think it’s because the other carrier was too heavy with the rest of the setup.

Wow that is interesting; I wouldn't have guessed the .308 would be giving you any problems.

I will say I had all sorts of problems like you described in my first 20" .260 AR10 Lilja barrel. Despite having an adjustable gas block, I'd get ejector marks on literally everything; didn't matter if I slowed a 123gr down to 2400FPS, and only had the block one click further open from constant jamming. It would also warp the case head; to the point of actually making it so you had to really force it into a shell holder to reload it. This is using new blue box Lapua brass too.

I didn't mess with buffers beyond the standard AR10 rifle buffer personally; I just swapped to a Proof Research +2/ELGS 22" barrel, and the difference in brass was literally night and day. In addition to the gas port being drilled 2" further out, it was also ~.020 smaller (IIRC). Now days, that AR10 spits out brass that will rival bolt gun brass. I can get it to put ejector marks if I run slower powders like H4831SC, even in lower charge weights though.

Odd question, but have you broken any bolt catches?

 

[Jimmy James]

I have a bone stock PSA AR10 in 308 that is definitely over gassed. Leaves raised ejector marks on FGMM ammo/brass. Hell on brass all the way around but is very accurate. If I run 150 gr FMJ bullets at about 2400 to 2500 fps and crimp, gun works well and is still accurate. Still pops a primer every now and then and jams the trigger. Now I know why military ammo has crimped primers. If I had to do it all over again, I wouldn't.

 

[Delfuego]

What is (was) the Tubbs CWS?

https://www.midwayusa.com/product/1004741684/tubb-ar-15-cws-bolt-carrier-weight-system

The Carrier Weight System was a weight kit that went into the hole in the back of your your bolt carrier. It included a tungsten weight that slowed locktime and slowed the carrier speed. It made all the difference in my large frame AR. I didn't have or need an adjustable gas block. Ejector swipes were gone and ejections became very mellow and predicable.

 

[Delfuego]

Another thing. The gas ports on damn near every brand of AR barrels is different. There is no real standard. Combinations of gas port diameters, gas system lengths, carrier weights, gas tubes, gas blocks, buffer weights/springs and calibers can make troubleshooting issues on large frame AR's a royal pain in the butt.

 

[snert]

FWIW I have about 4000 308 Federal GM factory all fired in 700 bolt guns, 1x and all have that mark. I attribute it to soft as butter brass. I loaded it and ran it in an M1a, left it lay afterward. Out of a 700, I reload it 1x again then pitch it.

 

[6ShotsOr5?]

Wow that is interesting; I wouldn't have guessed the .308 would be giving you any problems.

I will say I had all sorts of problems like you described in my first 20" .260 AR10 Lilja barrel. Despite having an adjustable gas block, I'd get ejector marks on literally everything; didn't matter if I slowed a 123gr down to 2400FPS, and only had the block one click further open from constant jamming. It would also warp the case head; to the point of actually making it so you had to really force it into a shell holder to reload it. This is using new blue box Lapua brass too.

I didn't mess with buffers beyond the standard AR10 rifle buffer personally; I just swapped to a Proof Research +2/ELGS 22" barrel, and the difference in brass was literally night and day. In addition to the gas port being drilled 2" further out, it was also ~.020 smaller (IIRC). Now days, that AR10 spits out brass that will rival bolt gun brass. I can get it to put ejector marks if I run slower powders like H4831SC, even in lower charge weights though.

Odd question, but have you broken any bolt catches?

No, but it’s not an odd question.