Low Mass Bolt & Carrier in the AR10

[Ishallbie O'Cullkillin]

I shot a friends POF .308 carbine the other day and it seemed a lot nicer shooting than my Armalite AR10 carbine.I use a PRI QCB brake on it, and a Tubb carrier weight system with it, but the POF was able to get faster follow up shots. I would like to explore modifications that will reduce the recoil impulse of the carbine. Should I try A lighter bolt & carrier? Adjustable gas block? A lighter buffer or spring? A .308 BABC perhaps? Any input is helpful.

 

[toygunner]

Re: Low Mass Bolt & Carrier in the AR10

I would remove the carrier weight. The added mass cycling increases felt recoil. You could put an adjustable gas block on the rifle and cut it back a bit. I had a LMOS JP bolt/carrier in my DPMS 308, I didnt like it.

 

[Sebben]

Re: Low Mass Bolt & Carrier in the AR10

Another factor could be just the weight of the rifle. The heaver the rifle the less felt recoil there is. What's the weight of the AR 10 compared to the POF.

 

[redirt78]

Re: Low Mass Bolt & Carrier in the AR10

What setup was in your buddies POF? That will help to know. Was it the stock 308 carbine buffer/spring from POF?

 

[Ishallbie O'Cullkillin]

Re: Low Mass Bolt & Carrier in the AR10

With the carrier weight and rifle length FF handguard & other accessories they both weighed in at about 9 1/2 lbs. POF carbine is all stock parts. I'ts my belief that both 5R and polygonal twist rifling reduce pressure, and therefore, reduce recoil, how ever slight it may be. There's also the roller cam pin, not sure how that would help. The POF reminded me a lot of My FAL para carbine, but more accurate.

 

[squirrel_slayer]

Re: Low Mass Bolt & Carrier in the AR10

might be the difference of your gun being DI and his being piston driven? running a lighter buffer and carrier in a di gun could be a bad way to go. it will cause excellerated wear and tear on the gun. a gas block couldn't hurt things though. that way you could dial the gas down till it just locks the bolt. also if you handload maybe trying a lighter bullet with a faster powder can help. My practice load is a 110gr bullet over imr 4227(when doing off hand dynamic shooting)

 

[WARDOG]

Re: Low Mass Bolt & Carrier in the AR10

I lurk over at ARFCOM, and there are a lot of shooters that have gone to a reduced mass BC, futz'ed with the gas system, cut buffer springs, changed buffer weights, and it seems <span style="font-style: italic">all</span> found their rifles were less reliable than stock.
Gun manufacturers do their homework and cycle millions of rounds during testing before sending a product to market. They try to get 100% reliability using the widest range of mass marketed cartridge loadings.
Sure you can tweak the entire system to operate almost perfect for a given bullet weight, suppressor, full length buffer tube, gas port etc. But if you try and shoot inexpensive ammunition contrary to the premium ammo you usually shoot, expect problems.
You can build a supercharged engine, 12:1 compression with huge cam made to run on $6 per gallon 110 octane fuel, it'll run a 11 second 1/4 sure!. But if you put 87 octane pump gas from the local quikeemart, it aint going to run quite right.

 

[FromMyColdDeadHand]

Re: Low Mass Bolt & Carrier in the AR10

I've played around with AR15s and my LMT MWS trying to tame recoil. By tame, I mean the ability to stay on the scope and get back on target faster.

I'd say, in my testing, qualitatively, that the brake makes the biggest difference. I like the JPs and I have a BABC on my LMT. I've shot Surefire brakes on OBRs and that worked well also.

The second thing I find that makes the most differnce is gas regulation. I have an Jp upper with an adjustable gas block and LMOS carrier/spring/buffer system and that is just smooooth once you get it dialed in. I got the gun a little dirty getting a round zero and then ran some 55gr 223 ammo and got it to run well with that. It has run couple thousand rounds of 223 75gr ammo and some 556 loads with out a hiccup. Add in the brake and its like cheating.

On the LMT, I don't have an adjustable gas block, and I think LMT gasses their guns generously to make sure they run in combat conditions. The 16in barrels are carbine gassed and their 18+ barrels are rifle gassed. I prefer my 18SS barrel with the rifle gas. I swapped out the SOPMOD for the PRS and its rifle buffer/spring system. I still didn't get the performance out of it I wanted, so I went with Heavy Buffers SS heavy buffer. That really helped to tame down the recoil. Probably 300-400 rounds with that set up and no issues. With the BABC brake I now can watch my splash on targets, not problem and the gun is just more manageble- and more importantly to me- repeatable from shot to shot. I can 'ride' the MWS now, before it was just bucking me around with each shot.

So Brake, gas valve, operating system tweaking seem to be the best way) and also least intrusive with the brake, way to tame a gas gun. IMO.

FWIW, I thought most people say that piston guns are usually a bit harsher than DI guns- as a general rule.

 

[Ishallbie O'Cullkillin]

Re: Low Mass Bolt & Carrier in the AR10

I installed a PRI adjustable gas block and a P.O.F. roller cam pin yesterday and tested the AR10A4CAR today with a 168gr SMK, 44gr Varget load. I was able to adjust the gas down to one turn out from bottom with the H3 Buffer, and still cycle. I removed the buffer and replaced it with an AR15 3oz buffer and got it down to half a turn. Bottomed out, the case ejected, but would not pick up the next round. I had no idea that these rifles are so overgassed. It's still not like shooting .556, but I am really impressed with how tame the gun is now. I have a Spikes Tactical .308 Dyna Comp on the way. I wonder, how much better can it get? After the Dyna Comp, I'm going to compare to a friend's SCAR17, if I can get him to bring it out of the safe.

 

[redirt78]

Re: Low Mass Bolt & Carrier in the AR10

That's good information. I have a JP adjustable block on my 5.56 and I need to tweak it a little bit.

 

[Ishallbie O'Cullkillin]

Re: Low Mass Bolt & Carrier in the AR10

I tested the Spike's Dyna-Comp on my AR10a4 carbine yesterday, and can't really say that it's an improvement over the PRI QC brake as far as recoil reduction or sight picture retention off hand. I did realize that the three oz. buffer isn't going to cut it, and will switch back to the 5.3 oz buffer. 44gr of varget & 168smk's ran fine, but 43.8gr of H4895 & 168 AMAX would double feed. From my angle, the single biggest improvement so far has been the PRI adjustable gas block.