UBR on an AR-10

[firefighter238]

Looking for a cheaper solution to mounting the Magpul UBR to a DPMS compatible AR 10 lower. The biggest recommendation I can find online is to sped $125 on a Slash Heavy Buffer. Seems WAY to high for me. Suggestions?

[thvigil11]

I had an old 9mm buffer that I used. Its one of the steel heavy 9mm buffers, I had to cut it down about .5", i don't recall the exact amount. Redrilled the pinholes for the rubber piece. Then I used two tungsten buffers out of an old H2. The total weight came up to be 5.3oz. For me it was cheap because everything was in the spare parts bin. If you bought everything I think you'd still be about half of what a slashes would cost you.

[ray1970]

Doesn't the UBR use a standard carbine buffer/spring setup?

I know I've seen AR-10s with standard collapsible stocks.

Can't you just use whatever they put in those?

[thvigil11]

Doesn't the UBR use a standard carbine buffer/spring setup?

I know I've seen AR-10s with standard collapsible stocks.

Can't you just use whatever they put in those?

Longer bolt (ar10) inside a standard buffer tube requires a shorter buffer. Other option with normal stocks is to use an ar10 carbine tube, but a UBR is only available with an ar15 length tube.

[Delfuego]

You could try a H3 buffer and an adjustable gas block. Tubbs CS springs have always done me well in the past too.

[thvigil11]

You could try a H3 buffer and an adjustable gas block. Tubbs CS springs have always done me well in the past too.

A normal ar15 carbine buffer is too long to use with 308 bolt and a UBR tube. He needs a short 308 buffer. The DPMS 308 ones are short, but light weight. The Slash one is also short, but is equal to an h3 in weight. He was looking for a cheaper solution to cashing out for the Slash buffer.

[Delfuego]

A normal ar15 carbine buffer is too long to use with 308 bolt and a UBR tube.Roger that.

I didn't realize the UBR had a shorter tube. The DPMS CAR-10 buffer and an adjustable gas block would work, but he's still gonna spend $125-$150 on either. AR308 are way over gassed to begin with, no cheap solution eh?

[firefighter238]

Thanks for all the input! I'm going to try to machine down a standard carbine buffer and see how that works. If that doesn't work I have a 9mm buffer that I'll try to cut down. Either way I'll post details.

[Skully]

I had a standard AR15 issue UBR on my DPMS pattern 308 and it worked just fine for me.

No special anything, other than buffer and buffer spring for a 308 carbine, which incidentally came with my 308 lower when I bought it. :)


Use a little Google Foo and you will see a lot of examples.

Maybe the Armalite AR10 uses something special?



Doesn't the UBR use a standard carbine buffer/spring setup?

I know I've seen AR-10s with standard collapsible stocks.

Can't you just use whatever they put in those?


Longer bolt (ar10) inside a standard buffer tube requires a shorter buffer. Other option with normal stocks is to use an ar10 carbine tube, but a UBR is only available with an ar15 length tube.


You are correct Ray, you win the prize! :)

Not sure what the rest of you guys are all talking about or smoking???? [Coffee]



So in review, you CAN use your UBR, your just need the 308 CARBINE buffer and buffer spring.




What I had, a CMMG MK3 308 carbine lower. (http://www.cmmginc.com/product_p/38ca3e8.htm)

http://cdn3.volusion.com/ealcn.upcaf/v/vspfiles/photos/38CA3E8-2.jpg?1339146414

(http://www.cmmginc.com/product_p/38ca953.htm)

[Skully]

Here Firefighter saved you the trouble of searching.


Rainier arms buffer spring (http://www.rainierarms.com/?page=shop/detail&product_id=2639) $8.95


https://www.rainierarms.com//img/shop/product/07b95cc618db15a568986d3d3dd910f0.jpg


DPMS .308 Carbine Length Buffer Spring
DPMS 308 carbine buffer spring which can be used in conjunction with the DPMS 308 carbine buffer in standard sized AR15 buffer tubes. This combination allows you to use the AR15 buffer tube which is slightly shorter than the AR10 buffer tubes.




308 Carbine Buffer (https://www.rainierarms.com/?page=shop/detail&product_id=2638) $34.95

https://www.rainierarms.com//img/shop/product/6e2ce09d66d2e2d59e8cac4aa0490b52.jpg


DPMS .308 carbine buffer
DPMS 308 carbine buffer which can be used in conjunction with the DPMS 308 carbine buffer spring in [B]standard sized AR15 buffer tubes. This combination allows you to use the AR15 buffer tube which is slightly shorter than the AR10 buffer tubes.

[Skully]

Dammit! Now I want my 308 carbine again. [gohome]


Remember this RAY?

You were shooting my 308 in its first configuration? The not so soft to the shoulder TROY stock before my UBR. :)






http://www.youtube.com/watch?v=jOOReOvJwWM&list=UUER8_mAocMOnscppVHF8ICw& feature=player_detailpage

[ray1970]

Yep. I didn't like the Troy stock. Still don't.

[thvigil11]

I assumed our friend already knew about the regular 308 carbine buffer. I though he was looking for a heavy buffer solution. Then most you can squeeze out of a normal 308 carbine buffer is about 2.5oz. The slash buffer he mentioned is 5.4oz and helps with extraction and bolt speed issues. So I assumed he was looking for an alternative, heavy buffer for a 308 carbine. In my experience, its either make your own or buy slashes if you want a 308 buffer that's above 5 oz. Sorry for the confusion.

[Skully]

I assumed our friend already knew about the regular 308 carbine buffer. I though he was looking for a heavy buffer solution. Then most you can squeeze out of a normal 308 carbine buffer is about 2.5oz. The slash buffer he mentioned is 5.4oz and helps with extraction and bolt speed issues. So I assumed he was looking for an alternative, heavy buffer for a 308 carbine. In my experience, its either make your own or buy slashes if you want a 308 buffer that's above 5 oz. Sorry for the confusion.

When I first read Dustin's post what I got what his problem was, he wanted to put the UBR on his 308 lower and thought he had to do something super special to do it, nothing special about that.

Mine was a factory CMMG 16" upper and a factory CMMG lower other than the cosmetic accessories I switched out I never had a problem or fail with the stock 308 3.8 oz buffer.

We all know though that each custom rifle will always come with quirks and challenges once you get them done so who knows.

It is all good [Beer]

[thvigil11]

When I first read Dustin's post what I got what his problem was, he wanted to put the UBR on his 308 lower and thought he had to do something super special to do it, nothing special about that.

Mine was a factory CMMG 16" upper and a factory CMMG lower other than the cosmetic accessories I switched out I never had a problem or fail with the stock 308 3.8 oz buffer.

We all know though that each custom rifle will always come with quirks and challenges once you get them done so who knows.

It is all good [Beer]

Yeah no worries here, just the realization that we were talking on different levels. The heavy buffer fix is not so important on the midlengths, especially since CMMG pays attention to other things like proper port sizing and such. Its the carbine length systems in 308 that tend to run way overgassed and meet with extraction problems.

"We all know though that each custom rifle will always come with quirks and challenges once you get them done so who knows."

True words right there. Some times its fun to play with a challenge, other times you end up pulling all your hair out.

[Beer]

[ringhilt]

If you want to use the Magpul UBR stock on your AR10, go to www.762sass.com. They sell the special short and heavy buffer you need to use to work with the UBR stock. The standard carbine buffer is still a bit too long. The UBR stock uses a special shorty buffer tube. They also sell a slightly shorter buffer spring to go with it. Or just cut the standard spring down a turn or two.
The buffer should be about $50ish. The spring is about $10ish.

http://www.762sass.com/product.php?p=552&cid=7&session=04e7c848b95ac34e2fa2902c66f62569

[CO-Exprs]

Couple of points to consider. Buffers are pretty basic little parts. It's pretty easy to drive out the role pin, pop off the rubber bumper and fill it full of lead shot. I go a different direction though. As a Heavy Metal multigun competitor, I need recoil as low as possible for those fast courses. For that I need the best brake available (legal for my division) and the rifle needs to be set up tits. Heavy buffers are fine for helping slow down the carrier and deal with the over gassing, but a far better way to go is to switch to adjustable gas and low mass internals. The PRI and the Seekins adjustable gas blocks can be had for around $60 and both are excellent products. You will spend a little more to add the gas block, but it will really help with smoothing out the muzzle jump.

My personal set up is an 18" barrel with mid length gas, adjustable gas block, low mass BCG, JP captured buffer spring system, UBR stock and my own custom brake. My rifle runs very reliable and the muzzle just sort of dances around in the center of the target at 20yds. I can shoot 600yd targets and then jump up and hose paper targets at a dead run, like it was an 223. In 308 it is far better to dial the gas to where it should be, then to compensate for over gas with heavier parts. A PRI gas block, DPMS 308 buffer and spring will set you back $100 total. You can pull one of the weights out of the buffer to get the same reciprocating mass as a low mass bolt carrier. In the end you will have a much better shooting rifle and the UBR stock you wanted.

[firefighter238]

Again, it's good to see such good advice coming out from our members, its the best part about this site! My piece of advice, IGNORE all the other online forums who say to use the Slash Heavy Buffer, I didn't need to use it as well as others here and I'd NEVER recommend anyone pay $125 for just a buffer!

[CO-Exprs]

This is what I mean about tuning your AR10 to run properly. This is my JP 308 rifle with the gas dialed, my own brake design and full power 155gr ammo. Notice that even with low mass internals and the gas dialed in just right, the reciprocating mass still rocks the rifle a little. The lower the mass and operating pressure, the less the rifle will move. 308 is different from 223 in that you can't just drop on a nice brake and make it feel like an airsoft. A good brake will do a lot, but the whole platform needs to be tuned to give best results.



https://www.youtube.com/watch?v=EtT2mRj8FC0