Hello, I just bought an PSA AR10 in 308 Win. Took it out to sight it in with the same loads that I use in my M1A Supermatch which I think is a middle of the road load of 41grs of IMR 4895 with a Sierra 168gr bullet. I found that there are ejector marks on the bottom of the cases which indicate that they are high pressure. Should I use a different powder or just reduce my load. I haven't had time to do any more reloading but I thought I would ask people here on the forum what loads do they use for their AR10. Any help or suggestions would be appreciated. Thanks.
- Thread starter chama
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Ejector marks on brass fired from an AR-10 isn’t a reliable way to determine if its high pressure round or not. For some reason most AR—10s begin unlocking somewhat prematurely compared to AR-15s and other semi auto. Carrier weights, heavier buffers, adjustable gas blocks and the combination thereof help with this. I would get an adjustable gas block first and start experimenting and if it doesn’t solve your problems then I would get an H3 buffer if you don’t have one. You must make sure you have an A5/Vltor length buffer tube. I run the Armalite/Vltor length buffer tube, Tubbs flat wire spring and a fully adjustable gas block on my AR-10s. I no longer get ejector wipes unless I am getting into maximum charge territor.
ETA 41 grains under a 168 bullet should be well under pressure. Your rifle is unlocking early. I ran into this when I first started reloading in ‘06 using 4895, commer cases and SMKS. Once I added the items I listed above I was able to go 42.0 grains under a 178 hpbt in a M80 case without issue. I dropped down to 41.8 just in case on those really hot days.
ETA 41 grains under a 168 bullet should be well under pressure. Your rifle is unlocking early. I ran into this when I first started reloading in ‘06 using 4895, commer cases and SMKS. Once I added the items I listed above I was able to go 42.0 grains under a 178 hpbt in a M80 case without issue. I dropped down to 41.8 just in case on those really hot days.
Barrel length? Gas system -- rifle or mid-length? Collapsible stock? PSA's are famous for inadequate recoil systems, short gas tubes, etc etc.
If collapsible stock, the interior depth of the buffer tube should be about 7", the buffer should be about 2.5" long. The buffer will be too light at about 3.8 oz. You will need a heavier buffer at about 5.3-5.6 oz and a Sprinco "orange" spring. I used the Kaw Valley 5.6 oz buffer coupled with the Sprinco orange spring to fix mine. This 7" internal depth tube is probably what's on your PSA. The buffer/spring combination that comes standard on these guns is basically inadequate for use with the .308.
Another alternative would be the aforementioned A5/Vltor/Armalite buffer tube length with an internal depth of 7-5/8", which requires a buffer length of 3.25". The buffer will, again, need to be somewhere close to 5.5 oz. weight. Easiest way to do this length buffer tube would be to just get the Armalite kit: https://www.armalite.com/SACItem.as...Category=ac614400-ff09-4cdf-9d35-419a654e7201
That kit will insure you have ALL the proper recoil system parts designed to work together for a .308 AR.
You cannot mix buffer lengths or springs between the 2 designs.
The other common problem with the PSA "mid-length" PA10 is the gas tube length. Lock the bolt carrier to the rear and remove the magazine. Look up into the mag well at the gas tube. It should terminate widway of the cutout for the cam pin or even a little longer. If it does not reach at least the midpoint of that cutout then it is too short. The remedy is an "Armalite AR10 carbine length" gas tube. PSA uses an AR15 mid-length gas tube which would be fine if the gas port is properly placed on the barrel. Many times the port is more forward on the .308 barrels, and the gas tube winds up being too short.
The AR15 mid-length gas tube is about 11-3/4" long.
The Armalite AR10 carbine length gas tube is 12-1/16" long
Since your problem seems to be "overgassed" or "improper timing" then the buffer weight combined with the proper spring will most likely be the culprit.
If collapsible stock, the interior depth of the buffer tube should be about 7", the buffer should be about 2.5" long. The buffer will be too light at about 3.8 oz. You will need a heavier buffer at about 5.3-5.6 oz and a Sprinco "orange" spring. I used the Kaw Valley 5.6 oz buffer coupled with the Sprinco orange spring to fix mine. This 7" internal depth tube is probably what's on your PSA. The buffer/spring combination that comes standard on these guns is basically inadequate for use with the .308.
Another alternative would be the aforementioned A5/Vltor/Armalite buffer tube length with an internal depth of 7-5/8", which requires a buffer length of 3.25". The buffer will, again, need to be somewhere close to 5.5 oz. weight. Easiest way to do this length buffer tube would be to just get the Armalite kit: https://www.armalite.com/SACItem.as...Category=ac614400-ff09-4cdf-9d35-419a654e7201
That kit will insure you have ALL the proper recoil system parts designed to work together for a .308 AR.
You cannot mix buffer lengths or springs between the 2 designs.
The other common problem with the PSA "mid-length" PA10 is the gas tube length. Lock the bolt carrier to the rear and remove the magazine. Look up into the mag well at the gas tube. It should terminate widway of the cutout for the cam pin or even a little longer. If it does not reach at least the midpoint of that cutout then it is too short. The remedy is an "Armalite AR10 carbine length" gas tube. PSA uses an AR15 mid-length gas tube which would be fine if the gas port is properly placed on the barrel. Many times the port is more forward on the .308 barrels, and the gas tube winds up being too short.
The AR15 mid-length gas tube is about 11-3/4" long.
The Armalite AR10 carbine length gas tube is 12-1/16" long
Since your problem seems to be "overgassed" or "improper timing" then the buffer weight combined with the proper spring will most likely be the culprit.
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I appreciate the info.
43.5 of Varget over 185 Juggs was fine in a bolt rifle 24” barrel.
It crushed the brass with violent ejection forward in my 18” Proof AR10. 5.6oz buffer, SA agb bled almost wide open, rifle extension and Tubbs flat spring.
Just 1/2 grain lower is money. 2520 fps.
I get 2650 from the bolt gun 24”
FWIW, my 10 shot group load validation results compared to 3-shot of FGGM 168 @100YDS using mixed LC brass, CCI 200 primers, Hornady 155 OTM @2.785" COAL, 42.4gn 8208XBR, 2633 avg FPS, 10 SD, 27 ES out of a BA Hanson 16". Brass was not annealed and unknown times of firings, shots taken using a hasty rest (ammo can w/rag cloth). Now that I have an annealer I presume I'll be able to improve on that load.
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I probably realize a 10 group and 3 group shouldn’t be compared but more importantly, definitely limit every variable you can, especially the rest.
FWIT, anecdotally, I don’t anneal. You will have to decide for yourself. Brass life, etc.
FWIT, anecdotally, I don’t anneal. You will have to decide for yourself. Brass life, etc.
..so far I've seen an actual improvement in shoulder bump consistency, reduced springback, consistent neck tension/bullet seating once I began annealing, which have contributed to improvements so far as regards chrono readings. Holes on target has improved, but definitely not "single-hole", I'm just not that good, LOL
FWIW... the PA10 and the Aero M5's ( and DPMS ) use identical gas tube lengths, buffer weights, and the same AR15 length carbine buffer tube length. Those parts are DPMS Pattern.
Armalite uses a different parts. Those different parts are Armalite Pattern.
IMHO, it can be a Ford v. Chevy thing.
Both work, just different ways of achieving the results.
So the AR15 gas tube length ( DPMS Pattern ) does work, as well as the DPMS pattern AR15 carbine buffer tube length and 2.5" buffer.... But ... like all the Large Frame AR's I have seen... a little finessing can go a long way, much like your SuperMatch over a more basic M1A.
And to be honest, the lack of a milspec guideline for Large Frame AR's can make for some confusing parts issues. ( Armalite pattern v. DPMS pattern, and some odd balls thrown into the mix ( Bushmaster, etc )
I would consider a Quality Adj. GB ... as mentioned, your PA10 is most likely suffering from an "over-gassed" scenario. The gas port size on almost every .308 / 6.5CM barrel I have measured has been ( IMHO ) oversized.... PSA / DC Machine barrels included.... Criterions, Faxons, Ballistic Advantage, etc.
( Only my Krieger barrels have a more reasonable gas port size. )
And while a oversized gas port helps assure function under adverse / poor conditions... that same large gas port can be abusive on the brass, the various parts, and needlessly on you . Unlocking the Bolt while chamber pressures are still high.
And the volume of gas produced from firing a 308 sized cartridge is "double" that of a 5.56 ... so again, finessing is worth the time.
If the Adj. GB doesn't help limit the "brass abuse" then I would consider adding a 5.3oz 2.5" buffer ( KAK sells them ) and I have also had very good all around results with a Tubbs .308 Flatwire recoil spring. ( Or buy all the parts together )
FWIW, all my PA10's ( various barrel lengths , gas system lengths, buffer tube lengths , and barrel manufacturers , and even a Armalite patterns ) use SLR Adj. GB's ..opened about 6 of the available 15 clicks , heavy buffer weights and Tubbs 308 Flatwire recoil springs.
All of them ( PSA uppers and lowers ) function perfectly after adding all those parts, and while they all functioned without those added parts, I also could see the cyclic speed was abusing brass, etc... and after the added parts, they are very soft shooting and IMHO , a bargain Large Frame AR setup.
And with some other assm. "tricks" ( lack of a better word ) have proven to be far more accurate then I am. ( That 10th shoot of the group ! Lol )
My fired brass is much less "abused" from the heavier setups and limited gas flow.... all those parts together lowered the cyclic speed and bolt unlocking to a more moderate pace... allowing the brass to extract at a lower chamber pressure.
Oops. before I forget, make sure your ejector doesn't have on burrs or sharp edges on its face and the edges. Polish as needed
In case I missed it , what kind of groups were you getting with your reloads ?
Armalite uses a different parts. Those different parts are Armalite Pattern.
IMHO, it can be a Ford v. Chevy thing.
Both work, just different ways of achieving the results.
So the AR15 gas tube length ( DPMS Pattern ) does work, as well as the DPMS pattern AR15 carbine buffer tube length and 2.5" buffer.... But ... like all the Large Frame AR's I have seen... a little finessing can go a long way, much like your SuperMatch over a more basic M1A.
And to be honest, the lack of a milspec guideline for Large Frame AR's can make for some confusing parts issues. ( Armalite pattern v. DPMS pattern, and some odd balls thrown into the mix ( Bushmaster, etc )
I would consider a Quality Adj. GB ... as mentioned, your PA10 is most likely suffering from an "over-gassed" scenario. The gas port size on almost every .308 / 6.5CM barrel I have measured has been ( IMHO ) oversized.... PSA / DC Machine barrels included.... Criterions, Faxons, Ballistic Advantage, etc.
( Only my Krieger barrels have a more reasonable gas port size. )
And while a oversized gas port helps assure function under adverse / poor conditions... that same large gas port can be abusive on the brass, the various parts, and needlessly on you . Unlocking the Bolt while chamber pressures are still high.
And the volume of gas produced from firing a 308 sized cartridge is "double" that of a 5.56 ... so again, finessing is worth the time.
If the Adj. GB doesn't help limit the "brass abuse" then I would consider adding a 5.3oz 2.5" buffer ( KAK sells them ) and I have also had very good all around results with a Tubbs .308 Flatwire recoil spring. ( Or buy all the parts together )
FWIW, all my PA10's ( various barrel lengths , gas system lengths, buffer tube lengths , and barrel manufacturers , and even a Armalite patterns ) use SLR Adj. GB's ..opened about 6 of the available 15 clicks , heavy buffer weights and Tubbs 308 Flatwire recoil springs.
All of them ( PSA uppers and lowers ) function perfectly after adding all those parts, and while they all functioned without those added parts, I also could see the cyclic speed was abusing brass, etc... and after the added parts, they are very soft shooting and IMHO , a bargain Large Frame AR setup.
And with some other assm. "tricks" ( lack of a better word ) have proven to be far more accurate then I am. ( That 10th shoot of the group ! Lol )
My fired brass is much less "abused" from the heavier setups and limited gas flow.... all those parts together lowered the cyclic speed and bolt unlocking to a more moderate pace... allowing the brass to extract at a lower chamber pressure.
Oops. before I forget, make sure your ejector doesn't have on burrs or sharp edges on its face and the edges. Polish as needed
In case I missed it , what kind of groups were you getting with your reloads ?
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think the comments above regarding tuning gas are probably on the right on.
I had similar issues with my 308 gas gun at where I ran into pressure issues quickly. I built it myself and went through quite a bit of troubleshooting to get it to shoot. Couldnt go beyond 41gr of 4895, 43gr RL15, 42.6gr Varget or 4064 with 175 class bullets.
my load now is Lake City brass, 210M primers, 42.3gr of Shooter’s World Precision, and 178 ELDs going 2550fps and I don’t get ejector marks any more. i did upgrade my barrel, bcg, gas block, and buffer to Gucci parts as my rifle was more of a precision build but after installing JP bcg and SCS and tuning the SLR gb the brass comes out much cleaner
I had similar issues with my 308 gas gun at where I ran into pressure issues quickly. I built it myself and went through quite a bit of troubleshooting to get it to shoot. Couldnt go beyond 41gr of 4895, 43gr RL15, 42.6gr Varget or 4064 with 175 class bullets.
my load now is Lake City brass, 210M primers, 42.3gr of Shooter’s World Precision, and 178 ELDs going 2550fps and I don’t get ejector marks any more. i did upgrade my barrel, bcg, gas block, and buffer to Gucci parts as my rifle was more of a precision build but after installing JP bcg and SCS and tuning the SLR gb the brass comes out much cleaner
It's a 20-inch Bartlein barrel with a 1:10 twist from Craddock Precision. Thing freakin hammers now.
What type of barrel profile? I currently use 18" criterion hybrid contour. .750" gasblock and the m118lr chamber.
I was not getting quite that velocity last time I checked. You like the results?
@Quietguy88
I have the .936 heavy contour (think it's slightly heavier than the M110 contour) with Paul's match 308 chamber.
I'm pretty happy with it so far. Below is what it shot while doing load development. Haven't shot paper since, but the last time I ran my gas gun at a club match I cleaned a KYL rack at 450 yards which made me feel pretty darn good. Ended up shooting just ok the remainder of the match, but that's on me because I like to go fast
. I've taken it out to 750 yd at matches and it's performed very well. Accuracy is definitely there when I'm shooting prone, I just need to learn to shoot it better positional.
I have the .936 heavy contour (think it's slightly heavier than the M110 contour) with Paul's match 308 chamber.
I'm pretty happy with it so far. Below is what it shot while doing load development. Haven't shot paper since, but the last time I ran my gas gun at a club match I cleaned a KYL rack at 450 yards which made me feel pretty darn good. Ended up shooting just ok the remainder of the match, but that's on me because I like to go fast
. I've taken it out to 750 yd at matches and it's performed very well. Accuracy is definitely there when I'm shooting prone, I just need to learn to shoot it better positional.Attachments
Thanks to all who recommended Tubs flat spring. Afters pending 30 minutes trying to install it i finally got it in at which time the bolt travel wouldn’t allow it to retract far enough for the bolt stop to engage. After calling tech at Brownells and found that Tubs recommends cutting three coils from it. With this done i ended cutting my thumb and breaking the buffer retainer somehow and still couldn’t get the spring in. However it was a great learning experience. Guess i will stick with the spring that came with the gun.
