AR 10 build question

[C_R_Slacker]

I'm in the middle of my first AR 10 build and have a question about low mass vs standard mass carriers. It's a 16" 308 with intermediate gas length, rifle receiver extension and buffer, and an adjustable gas block. I plan on shooting suppressed most of the time. With that set up, should I stick to a standard weight carrier, or do you think a low mass would be ok?

Also, for long range (600-800 yards) out of a 16" barrel, would you recommend 155, 168, or 175 grain bullets?

 

[AZgeek]

No expert but here's my take. With that length gas system, I would go with the heaviest BCG I could find to increase dwell time. I just completed a 308 build where I went with the JP FMOS BGC and an SA adjustable gas block. Working flawlessly so far with about 300 rounds down the tube. For those distances, I would go with a 175/178 grain bullet.

 

[sinister]

If you're in the middle of the build and you're going to be shooting suppressed most of the time I'd go straight to rifle-length gas.

800 to 875 is tough to get with a 168 out of a 22 and 24-inch rifle, let alone with a 16 -- you'll also have to work your timing a bit since you'll have to tune a shorter gas tube length with the suppressor keeping pressure up longer (as the bullet clears the suppressor's length).

 

[AZgeek]

I went out of my way to find a rifle length gas system and I'm not shooting suppressed. Good advice! sinister.

 

[C_R_Slacker]

Ok, so what I'm gathering is with intermediate gas length as opposed to rifle, the full mass is going to be better suppressed because it will help delay the unlocking of the bolt? I've already bought the barrel, so it's a done deal. The bolt and gas block were all that I was lacking.

As far as long range, this isn't meant to be a true long range, precision rig, but if I can get pretty consistent hits at 600 on steel I will be happy. I'll probably go with a 1-6 or 1-8 so it won't have that much scope anyway.

But out of a short barrel 308, I didn't know if lighter, faster or heavier, slower would be the ticket.

 

[AZgeek]

"Ok, so what I'm gathering is with intermediate gas length as opposed to rifle, the full mass is going to be better suppressed because it will help delay the unlocking of the bolt?"

In theory yes. Hopefully someone else can chime in and confirm. There may also be a consideration for the type of recoil/buffer system you select in the mix. I decided not to get crazy here. Tubbs AR10 flat spring ($29) with an TacFire AR10 A2 style buffer ($11). Works just fine. Some nice 1-8x options out there. Not cheap but some within reason.

 

[C_R_Slacker]

I went flat wire spring with rifle extension and buffer. Surely with an adjustable gas block I'll be able to make it work. For what it's worth, I emailed JP and whoever responded said he would use a low mass in my situation, so who knows.

 

[AZgeek]

I think the FMOS was meant to keep things "mil spec" (using that term loosely) and/or simply add more weight for those who did not want to invest in an adjustable gas system. But your right, who knows!

 

[Bigjake83]

I'm in the middle of my first AR 10 build and have a question about low mass vs standard mass carriers. It's a 16" 308 with intermediate gas length, rifle receiver extension and buffer, and an adjustable gas block. I plan on shooting suppressed most of the time. With that set up, should I stick to a standard weight carrier, or do you think a low mass would be ok?

Also, for long range (600-800 yards) out of a 16" barrel, would you recommend 155, 168, or 175 grain bullets?

The BCG has very little if any effect on your Dwell time, only thing a Full Mass BCG will do is make your rifle more reliable when running Dirty, due to the increase in reciprocating mass. Also keep in mind it will amplify your recoil impulses. If Dwell time needs to be Tuned call Slash's Heavy Buffers and they will be happy to guide you in your endeavors.

As stated above I would also recommend a Full Mass BCG, simply because of how nasty the carbon blowback is when running a Can. If you want a JP Low Mass system you can do that as well just make sure you have the complete system, LOMAS BCG, AGB, JP SCS with tungsten weights and stiffer spring. If you're still on the fence call and talk to Dave at JP, he is the head engineer there.

For Ammo i would stick with 168's and 175's, because they just plain work! And the new Hornady 155gr palma ammo is good, but worthless in a 16" barrel.

 

[C_R_Slacker]

Awesome, thanks for the info.