Short Barrel 308 Carbine Gas

[DRAM40A1]

For those of you with experience with SBR 308, I'm wondering what buffer and springs I should start with with a 12.5" Craddock Precision barrel? I'm going to run a brace on it and file for SBR stamp. I assume it will need to be heavy but which weight specifically? I have a XH Slash buffer that works in an extended carbine length tube but I'm assuming the arm brace tubes are standard carbine length? Oh and I have a nickel boron Aero carrier and JP enhanced 308 bolt, if that helps...

 

[DRAM40A1]

I ordered an SBA3 today and it ships with a mil spec carbine extension so I guess that opens up all kinds of possibilities.

 

[Craigm63]

do you have or have you already ordered the barrel?

 

[DRAM40A1]

I bought the barrel here on the Hide. A 12.5 Craddock Precision Bartlein 1-10...

 

[Landon4]

Why are filing for an sbr stamp if your running a pistol brace, I’ve been thinking about doing a short barreled .308 myself as I have a built lower just needing an upper

 

[DRAM40A1]

Why are filing for an sbr stamp if your running a pistol brace, I’ve been thinking about doing a short barreled .308 myself as I have a built lower just needing an upper

Because for $99 I can put a brace on it and shoot it now, while I wait on the approval and I’d much rather run it with a Gen 2 UBR after it becomes an SBR.

 

[ShooterwithNoName]

Probably running the brace in the meantime while the stamp comes through would be my guess.

I'm building a similar short barreled 308, but I'm using a 14.5" BA barrel with a pinned FH. Should have a nice balance to it. I wanted it for use as a carbine in 308, and something to beat around on without tearing up my nice, long barreled upper.

Interested in how yours shoots, that's a nice barrel albeit on the shorter side. Other than the velocity drop it should still shoot fairly accurately. How are you going to manage the muzzle flash? I'm on the fence trying to decide what to do on my 14.5".

Edit...
Forgot to mention, I'm running a KAK Heavy Carbine buffer. I've only run it on a 16" barrel but it does the job.

 

[Landon4]

Because for $99 I can put a brace on it and shoot it now, while I wait on the approval and I’d much rather run it with a Gen 2 UBR after it becomes an SBR.

I gotcha, yeah a bigger stock is more comfortable than the braces, good luck with the build man I’m curious to see it, I was planning on running a 14.5 barrel on mine once I finish up my ar-9 build I’ll probably jump on this one

 

[DRAM40A1]

I saw KAK has flash cans. If I can tame the gas, I may use my TBA Ultra 9 on it. I’m sure most of the time I’ll just shoot it with a brake and let it be obnoxious! LOL

 

[Landon4]

I had a flash can on 9mm ar I would like to run my 14.5 barrelled .308 suppressed

 

[DRAM40A1]

That’s my plan..

 

[Landon4]

Sweet Hell yeah man

 

[Raffica762]

I have 14.5" 308 and by far my favorite hunting set up.. world great with a can the carbine gas is nice not much blow back

 

[DRAM40A1]

I mocked up the handguard a couple days ago. Tracking says the barrel will be here Saturday so it won’t be long.

 

[bfoosh006]

I may have misunderstood... does your 12.5 barrel have a carbine length gas system ?

Or a carbine length buffer system ?

 

[DRAM40A1]

I may have misunderstood... does your 12.5 barrel have a carbine length gas system ?

Or a carbine length buffer system ?

I may have misunderstood... does your 12.5 barrel have a carbine length gas system ?

Or a carbine length buffer system ?

Both, I now have the brace and it shipped with a mil spec carbine lenght buffer tube. I will likely order a XH 308 carbine buffer from Slash, or if it's legal, switch to a 7 3/4 buffer tube and run the 8.5 ounce XH carbine buffer and rifle spring from Slash. I already have it on hand.

 

[DRAM40A1]

I've read, yea, we know how that goes, that 13.5 is the max allowable length of pull on an AR Pistol...With the 7" carbine extention its about 13.25" Obviously with the 7 3/4" extension it's about 13 3/4. I just don't run afoul of any NFA rules and regulations. I guess I just need to file for SBR and put a stock on it and be done with it!

 

[bfoosh006]

Do you happen to know the gas port size ?

And have you considered a Adj. GB or such ?

 

[BLDTYLRY]

I'm running a 12.5" AR308 SBR and my one recommendation to you is use an adjustable gas block. SLR or Superlative Arms are my go to.

 

[DRAM40A1]

I will have the barrel Saturday according to the tracking number. I do have a Superlative Arms Adjustable gas block. I’ll try and measure the gas port.

 

[bfoosh006]

I'm running a 12.5" AR308 SBR and my one recommendation to you is use an adjustable gas block. SLR or Superlative Arms are my go to.

I used to say the same manufacturers, and they both make very good products ( I have about a dozen SLR's, none suppressed ) ... but have seen quite a few blown out vent flaps from both of those brands when used a lot with suppressors.

I now wonder if the GB with screw in ( and tuneable for port size ) might not be a better system... granted not as easily adjusted by any means... but no bent vent parts either.

I would "think" it would be even more important using a short carbine GS in a .308 / 6.5CM

This is what I mean...
http://www.blackrivertactical.com/concrete5/customtune-gas-port/

 

[bfoosh006]

I can't seem to be able to find the photos of what I am talking about...

But the point is, you are going to have some serious pressures from the carbine GS and it being suppressed going through the Adj. GB "vent" systems if your gas port is "large" at all.

Anyway to measure the GP size ,it is still an important thing to do just so you can decide on a direction Adj. GB wise. ( IMHO )

 

[DRAM40A1]

I can't seem to be able to find the photos of what I am talking about...

But the point is, you are going to have some serious pressures from the carbine GS and it being suppressed going through the Adj. GB "vent" systems if your gas port is "large" at all.

Anyway to measure the GP size ,it is still an important thing to do just so you can decide on a direction Adj. GB wise. ( IMHO )

BTW, the majority of the time, it will be fired unsuppressed with handloads with lighter bullets and faster powder. I’m hoping that helps with function.

 

[Raffica762]

I run 110gr to 130gr with R7 in my 14.5 308 oh man killed many of deer

 

[bfoosh006]

I run 110gr to 130gr with R7 in my 14.5 308 oh man killed many of deer

Just Out of curiosity, what Gas length ?

 

[Raffica762]

Carbine gas ..I have found carbine length has less blow back when running a can ..my rifle length gas upper makes me cry all the gas

 

[bfoosh006]

Carbine gas ..I have found carbine length has less blow back when running a can ..my rifle length gas upper makes me cry all the gas

Interesting.. I would have assumed the contrary. Thank you.

 

[Raffica762]

I know right I dont know why I built a 10.5" sbr for my dad and its carbine length i feel no gas in the face at all put the same can on my 18" bbl rifle gas it's like being punched in the face

 

[DRAM40A1]

I can't seem to be able to find the photos of what I am talking about...

But the point is, you are going to have some serious pressures from the carbine GS and it being suppressed going through the Adj. GB "vent" systems if your gas port is "large" at all.

Anyway to measure the GP size ,it is still an important thing to do just so you can decide on a direction Adj. GB wise. ( IMHO )

To the best of my ability I measured .0870. I attempted to install the barrel tonight but obviously the barrel nut is too small to fit completely over the barrel extension. I sent an email to Centurion to see what the remedy will be. Bummer!

 

[DRAM40A1]

This is as far as the barrel nut will thread on to the receiver.

 

[bfoosh006]

This is as far as the barrel nut will thread on to the receiver.

Does the barrel nut screw fully in place without the barrel ?

And will the barrel nut fully slide down just the barrel .. to the collar ?

 

[DRAM40A1]

It slips over the barrel and stops at the barrel extension. Apparently, this is a known issue to Centurion. I sent an email explaining my issue and Corrie has sent a package with a Gen 2 barrel nut and wrench.

 

[bfoosh006]

Nice... gotta love good CS.

 

[corey4]

I saw KAK has flash cans. If I can tame the gas, I may use my TBA Ultra 9 on it. I’m sure most of the time I’ll just shoot it with a brake and let it be obnoxious! LOL

I put in an email to Zak about using the U9 on a 308 SBR. He said no shorter than 14.5, so that leaves me with having to use my saker.

I'm doing the pistol build as well while I wait for the form one. All the parts should be here in about a week.

Aero m5e1 upper/lower
Toolcraft bolt
BA 12.5 carbine
SLR AGB
SBA3
Saker762

 

[Ripdog28]

If you want to use the XH grab a Vltor A5 buffet tube. They make pistol A5 tunes as well. I’m running a slash XH in a Standard Vltor A5 and love it.

If not, I may have slash’s 308 buffer laying around. I’ll look if you may want it.

 

[Raffica762]

Oh man I'll bet the A5 setup is sweet on 308

 

[DRAM40A1]

If you want to use the XH grab a Vltor A5 buffet tube. They make pistol A5 tunes as well. I’m running a slash XH in a Standard Vltor A5 and love it.

If not, I may have slash’s 308 buffer laying around. I’ll look if you may want it.

I have an XH on a POF 308 in a Gen 2 UBR. Until installing that XH, that thing was nothing but trouble.
Let me know which 308 Carbine buffer you have. I think there are two different weights, correct?

 

[Gunfighter14e2]

Because for $99 I can put a brace on it and shoot it now, .

Only depending how it's listed on the 4473. If it's listed as a rifle, thats a no-no. If listed as receiver or pistol yes. Even if it was listed as a pistol or receiver, filing paper work to reg as an sbr brings issues.

 

[DRAM40A1]

Only depending how it's listed on the 4473. If it's listed as a rifle, thats a no-no. If listed as receiver or pistol yes. Even if it was listed as a pistol or receiver, filing paper work to reg as an sbr brings issues.

It’s on the 4473 as a receiver.

 

[DRAM40A1]

Only depending how it's listed on the 4473. If it's listed as a rifle, thats a no-no. If listed as receiver or pistol yes. Even if it was listed as a pistol or receiver, filing paper work to reg as an sbr brings issues.

What type of issues are you referring to?

 

[Ripdog28]

I have an XH on a POF 308 in a Gen 2 UBR. Until installing that XH, that thing was nothing but trouble.
Let me know which 308 Carbine buffer you have. I think there are two different weights, correct?

just checked and I actually sold the Shash 308 buffer. only have a cheap no name 308 buffer in my box of goodies. sorry bro.

 

[DRAM40A1]

I may have misunderstood... does your 12.5 barrel have a carbine length gas system ?

Or a carbine length buffer system ?

I lied...It has a mid length gas system and functions with a standard gas block, Aero NIB bolt carrier group, and Heavy JP Silent Captured Spring. I built it up this afternoon and test fired it with South African ball. Going to load up some 155 AMAXs with 8208 XBR tomorrow and see how that goes.

 

[bfoosh006]

Mid Length is a big ( much better ) difference.

Looking forward to your results !

 

[DRAM40A1]

I changed the buffer tube to an extended carbine and am now using an XH Carbine and rifle spring from Slash.
It’s still a little overgassed so I will be adding an adjustable gas block. I just wanted to see if I could tune it with burn rate...First I tried 8208 XBR and 155 AMAX, Hornady match brass and CCI 200 primer with somewhat acceptable results but switched to AR Comp and worked up to find the max charge. I started at 42 and worked up to 45 in .5 grain increments. I’m onto something here as all of the test rounds went into about 1.25 inches. 45 grains showed pressure so I’m going to back down and do a ladder this weekend. It’s also compressed with a 155 at 2.80. The cases are very clean and in surprisingly good condition after firing.