12.5” 308 SBRs and related

[GorillaTactics2089]

So, I’m looking at doing a .308 12.5-13” SBR. Just wondering who all has done this and what parts were used as far as gas tube length, buffers, and what luck y’all are having with what ammo and such. Mine will be suppressed with a HuxWrx flow through. I’ll end up putting hand loads in it. Just getting a feel for y’all’s most reliable setups.

[shepp]

@Rsquared

[shooterrex]

Once upon a time Sig sold a bunch of 12" 308 barrels to CDNN Sports. Several from this forum built pistols/sbr's from these barrels. They had a really weird gas port location. White Oak Armory makes custom length gas tubes. I built 2 pistols. Both run and shoot fine. Not suppressed though. Faxon also makes those length barrels if I remember correctly. 

Armalite 308 carbine buffer tube and spring w/a h3 buffer.

Both pistols run 147-175gr ammo just fine.

Edited Monday at 03:37 PM by shooterrex

[98Z5V]

^^^  I have one of those, and kind of pioneered the gas tube length issue - how to measure, and get what you need.  Those barrels were released with two different gas port locations.

So, I have that 12.5" barreled .308 Win gun, and a 13.5" barreled .308 Win gun.

OP, if you run into issues building one of these, post up here.  Both mine run like a pissed off Banshee...

Edited Tuesday at 02:55 AM by 98Z5V

[GorillaTactics2089]

3 minutes ago, 98Z5V said:

^^^  I have one of those, and kind of pioneered the gas tube length issue - how to measure, and get what you need.  Those barrels were released with two different gas port locations.

So, I have that 12.5" barreled .308 Win gun, and a 13.5" barreled .308 Win gun.

OP, if you run into issues building one of these, post up here.  Both mine run like a pissed off Banshee...

Absolutely brother. You running fixed or adjustable gas blocks? Every 10 I own has superlative arms adjustables.

[98Z5V]

Non-adjustable.  I believe in balancing the gas system to the recoil system.  Get the gun right first, before you introduce suppressors.  After suppressor introduction, if you need to change to an adjustable gas block - that's when you do it.  Not out of the gate.  Make the gun right, first.  

[GorillaTactics2089]

2 minutes ago, 98Z5V said:

Non-adjustable.  I believe in balancing the gas system to the recoil system.  Get the gun right first, before you introduce suppressors.  After suppressor introduction, if you need to change to an adjustable gas block - that's when you do it.  Not out of the gate.  Make the gun right, first.  

I like that. To be fair, I’m planning on running a flow through so it should run quite well on a non adjustable.

[98Z5V]

1 hour ago, GorillaTactics2089 said:

I like that. To be fair, I’m planning on running a flow through so it should run quite well on a non adjustable.

Get the Gas System and Recoil System balanced - and it should do great with a flow-through, and non-adjust block.   Suppressed and unsuppressed. 

Tell me what your barrel config idea is, and I can tell you what the gas port diameter should be. For a 12.5, you should run a Carbine Gas System.  If you decide to run a 13.5, you can get away with a midlength gas system.  I can give you gas port diameters for both configs. 

12.5 and midlength gas is tough to pull off, even in a 5.56 gun.  Trust me.  I have a few of those.  Dwell time becomes the biggest issue.

Edited Tuesday at 03:28 AM by 98Z5V

[MtnMike]

On the topic of 308 SBRs, any thoughts on whether I could just swap this 10" upper out https://www.midwayusa.com/product/1028296351?pid=518598 with the current one on an out of production Windham Weaponry AR 308 with a 16" barrel. 

Love the old WW, it's been incredibly reliable and is quite accurate.  However, it's also a bit redundant now since I obtained a Daniel Defense DDV-V3.  I've already made a few mods to the WW to further lighten it.  Thinking a 10" barrel would make for a solid package for hunting in an area with a lot of undergrowth and generally short sight lines.

[GorillaTactics2089]

10 hours ago, 98Z5V said:

Get the Gas System and Recoil System balanced - and it should do great with a flow-through, and non-adjust block.   Suppressed and unsuppressed. 

Tell me what your barrel config idea is, and I can tell you what the gas port diameter should be. For a 12.5, you should run a Carbine Gas System.  If you decide to run a 13.5, you can get away with a midlength gas system.  I can give you gas port diameters for both configs. 

12.5 and midlength gas is tough to pull off, even in a 5.56 gun.  Trust me.  I have a few of those.  Dwell time becomes the biggest issue.

I’m doing a 12.5” carbine length. My goal is for this to run well suppressed and unsuppressed, be reliable, and not beat the crap out of itself. It’s gonna stay in the experimental state until I feel like it’s proven it’s to be reliable for carry. I run the piss out of all my runs so if it can’t keep up, back to the safe till I can get it right. 😂

[98Z5V]

17 hours ago, GorillaTactics2089 said:

I’m doing a 12.5” carbine length. My goal is for this to run well suppressed and unsuppressed, be reliable, and not beat the crap out of itself. It’s gonna stay in the experimental state until I feel like it’s proven it’s to be reliable for carry. I run the piss out of all my runs so if it can’t keep up, back to the safe till I can get it right. 😂

I can tell you what you need for a recoil system - but I want to hear from you what your planned recoil system is first - and discuss that further, if necessary. Let it rip.  What are you planning for your recoil system, and how did that come to be your conclusion...