AR10 Ejector Swipes Journey

[RldrNewby]

I’ve been getting persistent ejector swipes on two different big bore ARs (different calibers) I’ve been troubleshooting for awhile, & figured I would share my results.

Rifle 1: DPMS Gen2 24” Bull 7.62x51 with Rifle Length Gas, Heavy Full Mass Propriety BCG, AR10 Rifle Buffer/Tube, Standard AR10 Rifle Spring, & JP AGB .936 Journal.
Status: FINALLY RESOLVED!!!
Original Issues: Primer Flow with a raised crater/crown on primers, and Ejector Swipes, even with factory ammo. Ejector Gouges with a raised sharp burr occasionally when shot suppressed.
Trouble shooting done:
-Tried tuning AGB where it would barely lock back on an empty mag. No help.
-Installed AR Stoner AR308 Rifle 9.4oz Heavy Buffer. No help.
-Installed Tubbs Flat Wire AR308 Rifle Spring. No help.
-Got Headspace Guages. Closed on 308 No Go, but would not close on 308 Field Guage 1.640 (Min Chamber for 7.62 NATO is 1.6355 to 1.6445, so chamber is within spec).
-Reached out to Adam’s Arms & was able to get a small diameter firing pin/bolt assembly that was compatible with my DPMS Gen2 Bolt Carrier. Took measurements & re-checked headspace, & bolt was GTG. Test fired, & the small diameter firing pin/bolt completely fixed the primer cratering! Still got ejector swipes even with new bolt.
-Verified the ejector edge was beveled with a slightly rounded radius.
-Abandoned the idea of shooting the rifle suppressed as I don’t have a flow thru low back pressure can. Still got persistent ejector swipes, but no more gouges or burrs.
-Took the AR Stoner Heavy Buffer apart, took out the spacers, ground down an additional tungsten weight I had from an older carbine H3 buffer to fit, then reassembled the heavy buffer. It may’ve been subjective, but the marks seemed better, but still there.
-Did a load development starting low & working up, 3-4 thou shoulder bump, Hornady Brass 1x fired, GM210M Primers, 168gELDM, COL 2.800, & Norma 202 Powder. Amazing groups around 2550fps, but still had slight ejector marks at that pressure, which got worse as the loads got hotter.
-Ordered some PPU 7.62 NATO Brass, did a full workup on the brass, and repeated the same load development. Unbelievably great group for this rifle again with same workup using different brass & at 40.4gr N202 2554fps, I had 4 rounds go through the same ragged hole, with the 5th pulled slightly to the left 3/4”. The case heads on the PPU brass looked like they had been shot out of a bolt action rifle! Flawless, even at the highest load I tested, which was 41gr at 2591fps. I shot 8 rounds at each charge weight, 5 without Magnetospeed V3 Chrono attached to see unadulterated group distribution, & 3 rounds with the Chrono attached to gather MV. There wasn’t a single hint of an ejector swipe, imprint, or glint on ANY of the brass, & there were still no primer issues! Success!

Now on to the problem child…

Rifle 2: Aero M5E1 AR10 6.5 Creedmor build. Aero Full Mass Nitride 308 BCG and small firing pin Bolt, Proof Research 22” Carbon Wrapped CAMGAS Barrel with Rifle Length +2 Gas System. AR10 Rifle Length Buffer/Tube, AR Stoner 9.4oz AR10 Rifle Heavy Buffer, Tubbs AR10 Rifle Flat Wire Spring, & Superlative Arms AGB with Bleed-Off Option, 0.875 gas Journal.
Status: Ongoing, still unresolved.
Issue: Same as Rifle 1, except I never had Primer Flow issues with this bolt, just persistent Ejector Swipes, even with factory Ammo.
Trouble shooting performed: Tried everything I tried on Rifle 1 on Rifle 2, except that I didn’t need a new bolt on this one, & I haven’t had time to try adding another weight to this buffer. Bolt does not Close on No Go Guage. I did try three different types of brass, Hornady factory ammo, Lapua, and Nosler. Lapua seemed to fair slightly better than the others, but who wants to chew up Lapua Brass in a gasser? If I could get it to look like the PPU 7.62 NATO Brass, life would be great. I have tried adjusting the gas block from both the choked off end till locking on an empty mag, to going from fully turned out on the bleed off mode turning in till locking back on an empty mag, but still get ejector swipes. Load development was done using 1x fired Nosler Brass, GM210M, 3-4thou bump, 140g ELDM at 2.800 COL, & H4350, and I had ejector swipes at each charge weight from 2621fps to 2715fps. The swipes were not very noticeable until I got to 40.9 at 2664fps, and were getting significant at 41.2gr 2685fps and turned to burrs on a couple cases at 41.5gr 2715fps.
Prognosis: I’m hopeful adding a little more weight to the buffer will delay unlocking of the bolt just enough to be able to load to 2664fps, & hoping if I use Lapua Brass in a new Load Development to do so, maybe it will be a little tougher than factory Hornady American Gunner 140gBTHPs, & Nosler Brass. I’ve completely given up on shooting this rifle suppressed without a flow through suppressor as well.

I’m open to any recommendations or thoughts

 

[Hecouldgoalltheway]

I solved this by reloading hornady brass and only being slightly concerned if I can't find it.

I keep a flat file on my reloading bench and I swipe the case heads one stroke when I see it

 

[mewillis]

Read about the springs here, might be a solution for you.

Sprinco USA -- Recoil Solutions

 

[newguy2k3v2]

I used to have ejector swipe issues with an older Lmt 308. Swapping to a dual ejector bolt cured all that

 

[RldrNewby]

I solved this by reloading hornady brass and only being slightly concerned if I can't find it.

I keep a flat file on my reloading bench and I swipe the case heads one stroke when I see it

I like that approach. Heck of a lot less stressful!

 

[msgriff]

Did you mean extractor swipes, or are you talking about ejectors?

ETA cut and paste: "Issue: Same as Rifle 1, except I never had Primer Flow issues with this bolt, just persistent Ejector Swipes, even with factory Ammo."

 

[RldrNewby]

Read about the springs here, might be a solution for you.

Sprinco USA -- Recoil Solutions

Just visited site & tried to read up on it. If I understood it correctly, the green might be an option, but the rest seem to be for Carbine Buffer Tubes/Buffers, so I think I’d have to switch Buffer Tubes to a Carbine Adjustable style & go with Carbine Buffer to try them, right? Currently using an A2 Rifle Buffer Tube & the longer Rifle Style AR Stoner 9.4oz Heavy Buffer.

 

[RldrNewby]

Did you mean extractor swipes, or are you talking about ejectors?

Ejector. On the milder loads, you see the faint circular outline of the the hole the ejector rides in, but when under more pressure like suppressed or hotter loads (some being factory), the brass flows slightly into the ejector hole when the bolt is unlocking & rotating, causing it to shear off the brass that was flowing into the hole making a sideways smear where the ejector was.

When testing suppressed, I saw on a cold bore, the first round looked completely fine, like fired from a bolt gun, but all subsequent shots afterwards would have the swipes, some bad enough to have a sharp burr. Very odd to me. Residual gas in the system have more density than air?

 

[RldrNewby]

I used to have ejector swipe issues with an older Lmt 308. Swapping to a dual ejector bolt cured all that

Will keep that in mind. Oddly enough, the proprietary bolt that came with the DPMS Gen2 did have dual ejectors & the larger diameter firing pin/hole, & I was having swipes with it too, but that was earlier on in my troubleshooting. The PPU 7.62 NATO brass fired from that rifle now rivals brass fired from a bolt rifle.

 

[msgriff]

Personally, I think that your gas system and buffer/spring selection is ideal. If you're confident with your loads, that leaves the bolt ejector design.

 

[RldrNewby]

Personally, I think that your gas system and buffer/spring selection is ideal. If you're confident with your loads, that leaves the bolt ejector design.

The ejector on this Aero Bolt is completely domed over rounded, unlike most I’ve seem, which typically are flat with slightly radiused chamfered edges. I did measure the length of the ejector, took it out & swapped it with a traditional shaped ejector (same OEM spring that came with the bolt), but the results were the same. I will say that test was done during my initial trouble shooting when I was still using the AAC SR-7 suppressor on it tho. I put the original ejector back in it afterwards when I didn’t see any improvements. Can a tight extractor cause ejector smears? Reason I ask, is the OEM bolt config was REALLY tight on the extractor. It arrived with an outer spring, inner spring, and two O-Rings! I was leaving tiny score marks on the rim of the case where the furthest ends of the extractor were snapping over the rim! I took the extractor out, polished the edges, & removed one O-Ring, then reinstalled. The case rims seem much better now, & ejection is at 4 o’clock about 6 ft away when shooting off a bench. Also, I read somewhere that some ppl recommended chamfering the hole the ejector rides in. I could try that, but I’m worried that would give more available area for brass to flow into? I can live with the ejector smears I have now, but I definitely want to do all I can do to mitigate them, & live with them if I can’t. That Proof Barrel is really accurate, & I really wanna make this system work. No charge weights I’ve tested in load developments have been over an inch!

 

[msgriff]

The ejector on this Aero Bolt is completely domed over rounded, unlike most I’ve seem, which typically are flat with slightly radiused chamfered edges. I did measure the length of the ejector, took it out & swapped it with a traditional shaped ejector (same OEM spring that came with the bolt), but the results were the same. I will say that test was done during my initial trouble shooting when I was still using the AAC SR-7 suppressor on it tho. I put the original ejector back in it afterwards when I didn’t see any improvements. Can a tight extractor cause ejector smears? Reason I ask, is the OEM bolt config was REALLY tight on the extractor. It arrived with an outer spring, inner spring, and two O-Rings! I was leaving tiny score marks on the rim of the case where the furthest ends of the extractor were snapping over the rim! I took the extractor out, polished the edges, & removed one O-Ring, then reinstalled. The case rims seem much better now, & ejection is at 4 o’clock about 6 ft away when shooting off a bench. Also, I read somewhere that some ppl recommended chamfering the hole the ejector rides in. I could try that, but I’m worried that would give more available area for brass to flow into? I can live with the ejector smears I have now, but I definitely want to do all I can do to mitigate them, & live with them if I can’t. That Proof Barrel is really accurate, & I really wanna make this system work. No charge weights I’ve tested in load developments have been over an inch!

I was referring more to trying a dual ejector design, as posted previously. It sounds like you have been very thorough and methodical, so I hate to suggest anything that may end up just throwing more money at it.

 

[newguy2k3v2]

The two on the left are LMT and the right is an Armalite. I had constant swipes with the single ejector Lmt. I believe it is because the ejector has such a large diameter and it ends up under so much of the case. Swapped to the double ejector and they’re gone with all but the hottest of loads. Even some that I ran too hot and popped primers on only give a slightly shiny smear, no edges or burrs. I believe the smaller diameter and more outboard position helps greatly. They’re mostly under the rim. The Armalite bolt is the middle ground and I have never had any real gripes with that design. If I had smears, it was too hot anyway.

All of these run the .068” or whatever the original(small) firing pin diameter is. I’ve never had cratering issues.

 

[RldrNewby]

The two on the left are LMT and the right is an Armalite. I had constant swipes with the single ejector Lmt. I believe it is because the ejector has such a large diameter and it ends up under so much of the case. Swapped to the double ejector and they’re gone with all but the hottest of loads. Even some that I ran too hot and popped primers on only give a slightly shiny smear, no edges or burrs. I believe the smaller diameter and more outboard position helps greatly. They’re mostly under the rim. The Armalite bolt is the middle ground and I have never had any real gripes with that design. If I had smears, it was too hot anyway.

All of these run the .068” or whatever the original(small) firing pin diameter is. I’ve never had cratering issues.View attachment 8132744

The bolt with the dual ejectors in that pic is a really interesting design. I kind-of like it. Almost looks like each ejector is partially rebated into an area of the bolt where the case doesn’t even make contact, which would reduce the surface are of the case that gets exposed to forces great enough to allow brass flow. My DPMS Gen2 7.62x51 OEM proprietary bolt has dual ejectors, but they are much nearer to each other, & not recessed into the bolt face, & just as prone to swipes as the single ejector types.

 

[RldrNewby]

Update:
Issue seems to be fixed now on the Aero 6.5CM build. Ordered a Palmetto State Armory 6.5CM Small Pin BCG with Dual Ejectors partially rebated into the portion of the bolt face that doesn’t contact the case head. Was able to run a quick test using Lapua Brass un-suppressed, which was previously in the worst shape of all brass un-suppressed. In all fairness, the Lapua load was slightly hotter than the Nosler load, by about 25-30fps. I also shot a few Nosler Brass, with the suppressor on, which previously gave me burrs on occasion. The new BCG made a world of difference for the better on both brass makes. All the preliminary measurements I had taken of the new bolt were the same, to within a couple thou, as the Aero OEM BCG, so I don’t believe the smears & glinting were a headspace issue. Thinking maybe it was more of a difference in the bolt face & ejector design? Who knows. Workin fine now, & I’m happy with it.

The pic below is how the PSA’s Dual Ejector design is layed out.

 

[otnot]

Just out of curiosity, was the new BCG heavier than the old one?

 

[RldrNewby]

Just out of curiosity, was the new BCG heavier than the old one?

I didn’t weight them, but holding each BCG in separate hands at the same time, they felt virtually identical. I know that’s not scientific; but unfortunately, I don’t have scales that will measure anything accurately over 16oz. All I have for anything over a pound are bathroom scales, & that wouldn’t be accurate enough for the job. They’re definitely both Full Mass. The specs on the original Aero M5 308/7.62 Bolt says it weighs 18.24oz, but I couldn’t find a weight spec for the PSA 6.5CM with the dual ejectors. Will mess around with it later today & see if I strip the bolts down & try to weigh them on my A&DFX120 as individual components, maybe I can get you some actual weight numbers for comparison.
Edit:
Just tried to weigh the BCGs as stripped individual components, but the carriers weighed too much, & errored out my A&D scale. Reassembled them, then put them on my digital bathroom scales, & for what it’s worth, each BCG weighed 1.2lbs or 19.2oz.