# Aero Precision .308 question



## blufire42 (Oct 28, 2015)

Hey guys, I am new to the AR10 builds, so if I purchased this: https://aeroprecisionusa.com/m5e1-complete-18in-308-cmv-em15-anodized-ch-bcg-gamma762.html, when I purchase a lower receiver, what does the buffer length need to be?

The Upper receiver says it has a Rifle length gas block, so do I need a lower receiver with rifle length extension or will a carbine length work fine? I don't really like their rifle length extensions as much as I like the carbine extensions.
https://aeroprecisionusa.com/lower-receivers/complete-lowers/l/m5/rifle.html


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## ChileRelleno (Jul 7, 2012)

You can use a carbine length tube and a DPMS Short LR-308 buffer, but even if the rifle functions with it it will be over gassed and you'll deal with a rougher action and heavier recoil.


I think you'd be better off with an A5 mid-length tube with a standard AR15 H buffer or standard rifle length tube and an AR10 rifle buffer.

***My first choice would be the A5 tube and an H buffer.***

Of course all three options are dependent on many factors/variables and any changes to these may affect function in a particular .308 rifle.
Gas port diameter, gas port location, gas leakage around the gas block and gas tube, type of ammo, projectile weight, projectile dwell time, BCG weight, type of recoil spring/spring strength, buffer type weight/arrangement and buffer tube length.


This is one of those put it together and see what happens moments.
How does it function when fired?

It may hand function just fine, but will it strip the second round, will it lock back on the last round, is eating up brass and so on?

Is the buffer heavy enough? Is it ejecting shells properly? Is it leaking gas?


Okay, it functions well enough overall, now this is where you start looking to fine tune it.
Spring strength, buffer weights, projectile weight, gas leakage and more.
Or maybe an adjustable gas block can solve one or more cycling issues.


LOL... G'luck with your rifle.
Its really not all that hard as it can be made to seem, unless you're gun doesn't want to function normally or you're a perfectionist.


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## blufire42 (Oct 28, 2015)

ChileRelleno said:


> You can use a carbine length tube and a DPMS Short LR-308 buffer tube, but even if the rifle functions with it it will be over gassed and you'll deal with a rougher action and heavier recoil.
> 
> 
> I think you'd be better off with an A5 mid-length tube with a standard AR15 H buffer or standard rifle length tube and an AR10 rifle buffer.
> ...


Thanks for the info. I am a perfectionist, but I'm not knowledgeable enough yet to be a practical perfectionist yet :nerd:


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## Realtor (Oct 1, 2007)

I have an extra H3 Buffer and spring here if you think you want to try it.


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## blufire42 (Oct 28, 2015)

Realtor said:


> I have an extra H3 Buffer and spring here if you think you want to try it.


I appreciate it Realtor, I'm waiting a bit to get some more funds for a lower receiver, but I might take you up on that once I do.


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## Realtor (Oct 1, 2007)

its here and I have an extra "enhanced gas ring" here in the box as well. Interesting build, let us know how it progresses.
Jim


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## CurDog (Nov 14, 2010)

I'd call AP and ask their CS which would be the better choice that'd give the best overall performance.


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