loads for AR-10 carbine

[bowyer19]

Anyone here loading for a.308 AR 10 carbine with carbine length gas system?165 gr SST worked well with IMR 4064 but I wanted to use the Sierra 155 gr Palma Match to get the velocity up in the 16" barrel. I tried CFE 223 but it seemed over gassed well below max and accuracy is inconsistent. IMR4064 is giving better accuracy but still a bit over gassed . Any suggestions besides an adjustable gas block?Maybe a powder slightly faster than the IMR 4064?

 

[LocoGringo]

What brand rifle is it? If DPMS, they are known for being overgassed. I understand you will not likely want to hear my answer, but get an adjustable gas block. It's what I use on mine.

I shoot an 18.5" barrel and use H4895 coupled with 175 gr SMK and 178 Hornady Amax. Obviously not blazing fast, but I'm getting 2560 FPS with those bullets.

 

[BigBore45]

here is a link to my load work ups with 155 gr SMK's

http://www.thehighroad.org/showthread.php?t=770828

Benchmark was a great combo for me. you can get load data from hodgdons website

 

[grubbylabs]

I am loading a 150 grain soft point with surplus H-335.

 

[bowyer19]

Yes the rifle is a DPMS,one of the new G2 carbines. 2560 seems blazing fast out of an 18.5" bbl using 175gr bullets. I may break down and get an adjustable gas block but probably not until I can also find the right size free float forearm.

 

[LocoGringo]

I'm using a stainless Criterion barrel from Fulton Armory. It's not a factory DPMS barrel. My handloads are warm, but not pushing limits. The adjustable gas block helps with tuning with a suppressor...a lot.

Tried Varget? It seems to be a favorite for .308. I use it in my bolt gun with the same bullets and get over 2700 FPS from a 24" Rock Creek barrel.

Been curious about the G2 DPMS. Would love to outfit one for Heavy Metal 3-gun.

 

[bowyer19]

I haven't tried Varget. I know it is one of my friends favorites. I will give some a try if I can find some.

 

[bogon48]

In the 2014 Hodgdon Annual Reloading Manual, there's an article on reloading for the AR-10. It's by Lane Pearce. The article starts on page 42. He tested a variety of popular powders and bullets.

One very accurate load was 43.5 gr of IMR 4064 behind a Sierra 168 gr HPBT in Lapua brass. Primer was a Federal 210M. He claimed .78" 100 yd accuracy.

Note that this manual is published as a yearly magazine. The 2015 version was released in Dec. I think, but I bought a 2014 copy at my LGS a couple weeks ago.

 

[grubbylabs]

Aside from the 150 grain soft point, I am having good luck with Hornady 168's over Varget and 180 grain sierra's over RL-15.

Mine is a GII Recon.

 

[redclay]

I shoot a DPMS LR308B and it loves 168 amax over 42 grains IMR 4895. Most accurate load I have ever found in any rifle. But my rifle does not like 150 grain projectiles have not found a load with any powder that groups less than 1-1/2 inch at a hundred yards.

 

[carbine85]

I'm reloading for a DPMS G2 Hunter. My best loads are with 168 gr SMK or equal and 41 gr of IMR4064. Any charge above that tends to damage the case and no improvement with accuracy. I do think it's over gassed but I haven't done anything yet to proof that to myself.
Varget and IMR4895 worked well but 4064 is better.
H335 wasn't very good.
I haven't used the chrony yet but plan to the next time out.
I also changed to magnum primers. The softer primers didn't hold up well to the heavier charges and my firing pin suffered from that. It took 5 weeks to get a replacement from DPMS

 

[PPS43]

What do you mean by "overgassed"? Case swipe (shiny crescent on bottom of the case where brass flows into ejector hole and is then swiped as the bolt rotates open)?

Keep in mind that some published .308 loads are tailored for bolt actions and might be simply too strong for AR-10. For example, Nosler range for 150 grain bullet is 44 to 48 grain of 4064, while Sierra is 39.1 to 45.5. I start seeing case swipe at 44, and even with factory Hornady American Whitetail ammo (which is very consistent).

 

[carbine85]

I think it's over gassed because the rifle cycles reliably on very weak loads and with loads on the high side it flattens primers, ruptures primers and the dual ejectors destroy the case and a lot of brass is left behind on the bolt face.

 

[PPS43]

Reliable cycling with weak loads is normal. There's quite a bit of margin in the design to ensure it cycles when dirty, in the cold, etc. Even with adjustable gas block you normally open it up until the bolt locks back, then add a click or two.

Now flattened and especially ruptured primers sound to me like pressure signs, not over gassing.

 

[BBDartCA]

Try BLc2 with mag primers. It's a match grade 308 powder that's fast burning and very clean. Ive had great luck with it in tanker 308 / 30-06 carbines. Like some other ball powders it can produces a lot of muzzle flash from a carbine.

 

[bowyer19]

My diagnosis of over gassing is from the ejection angle of the brass. With the CFE 223 the ejection angle is 1:30-2:00;with IMR 4064 it is about 2:30-3:00. With this rifle I am getting cratered primers with all loads ,factory and reloads, even with loads that show low pressure,i.e.primers not flattened at all. The last loads I fired were Federal 149gr ball ammo . The brass looks the same and it ejects slightly ahead of 3:00.

Does an adjustable gas block have any affect on accuracy?

 

[PPS43]

Ejection angle is tricky because it is affected by many factors. For example, I had stovepipes with factory ammo that I initially attributed to overgassing. Turns out that bolt carrier went back too far, bringing bolt front way past ejection port. Fixed by inserting two quarters under recoil spring.

Adjustable gas block does not affect accuracy.

 

[bowyer19]

i have been seeing a scratch mark on the outside of the brass about 3/8" from the base . That just may be the brass hitting the back of the ejection port? By under the spring do you mean at the back of the spring?

 

[bowyer19]

In other words, you pulled the buffer and spring and installed them behind the spring?

I did not wait for a reply because when I checked my rifle the marks on the outside of the case almost exactly matched the rear of the ejection port. The front of the bolt was behind the ejection port opening . It appeared the brass was being held against the bolt until it slammed it into the rear of the ejection port ;which then caused it to be flung way forward.

With 2 quarters at the back of the buffer spring: it put the bolt face even with the rear of the ejection port.The CFE223 load that had been going 1:30-2:00 was now going to 3:00 and some 147 ball to 4:00. Function was flawless and the bolt still locked back on the last shot. Further , there was no brass on the back of the ejection port or the shell deflector. Also, there were no extractor or ejector marks on the shell casings. Now I may have to revisit the CFE223 load development.

I guess this could be called "4 bit" gunsmithing.

Thanks PPS43 (and others)for the help I got here.