11.5 SBR AR15

[Mann427]

I'm looking to buy a 11.5" barrel for my AR15. Ive already looked over all of the paper work that I have to do, I just want to know if there's anything internal I NEED to do to the AR(diff. buffer,BCG,Gas tube, etc.) or if theres anything anyone can recommend. Any help will be greatly appreciated.

[JayBell]

in semiauto, generally no "special" parts are needed that CAN be useful in a Full Auto application.

Just get quality parts, and you wont have an issue.

I myself use a bone stock 11.5" chrome lined heavy barrel by bushmaster, on a Colt flattop upper, with a "pre Armalite name rental" Eagle Arms lower, and a DPMS fire control group, a bushmaster bolt, and a DPMS bolt carrier.

the closest thing i have to a "special" part in my SBR is a viton 0-ring under the extractor, but i use those in all my ARs, so no big deal... it provides firmer extraction.

I haven't made any adjustments to the gas port, or use a special buffer spring, or buffer, or special hammer spring, or anything else. it just works.

FA applications can have bolt bounce, or need carriers ramped, or need a lighter or heavier buffer, or buffer spring, or whatnot.

again, just get a quality barrel assembly, and you should be fine.

[Mann427]

Thanks dude.

[rockkrawler628]

Hey you wouldn't happen to be interested in a 11.5 SBR Upper w/ Gas piston, BIUS and Daniel defense rail would you?

if so check out my classified post in NFA items.

goodluck with your SBR!

[rockkrawler628]

oh but its LEFTY! haha

[ungawa]

Bolt bounce? It has a locking bolt. I wasn't aware of that, thanks.

[JayBell]

the term is "bolt bounce" but the more accurate term should be "carrier bounce"

pops up in shorter barrels where the guns cyclic is too fast, and when the carrier slams home against the barrel extension, it "bounces" back from the extension, unlocking the action enough that the descending hammer closes the bolt, and gives a light firing pin hit.

if yer firing a full auto with a short barrel, and getting a light primer strike, or something that appears to be hammer follow, check for carrier bounce.

as a note, this was the reason for the "H" marked heavy buffers in the m4 carbines

I myself use a 2 piece mechanical buffer by colt in my m16, was designed by colt for steady FA use in the 10.5" commando guns, thre buffer is weighted to give a "dead blow hammer" effect, ensuring the carrier is fully closed when the hammer hits the firing pin.

[ungawa]

the term is "bolt bounce" but the more accurate term should be "carrier bounce"

pops up in shorter barrels where the guns cyclic is too fast, and when the carrier slams home against the barrel extension, it "bounces" back from the extension, unlocking the action enough that the descending hammer closes the bolt, and gives a light firing pin hit.

if yer firing a full auto with a short barrel, and getting a light primer strike, or something that appears to be hammer follow, check for carrier bounce.

as a note, this was the reason for the "H" marked heavy buffers in the m4 carbines

I myself use a 2 piece mechanical buffer by colt in my m16, was designed by colt for steady FA use in the 10.5" commando guns, thre buffer is weighted to give a "dead blow hammer" effect, ensuring the carrier is fully closed when the hammer hits the firing pin.

That's great to know, thanks again. I haven't had any problems with the standard buffer on 11.5".

Why would the carrier bounce and the bolt unlock on FA only? It goes into battery at the same velocity regardless of fire mode. The only thing different in FA is the carrier trips the sear on it's way home. I'm not disputing, just asking. Thanks.

[JayBell]

That's great to know, thanks again. I haven't had any problems with the standard buffer on 11.5".

Why would the carrier bounce and the bolt unlock on FA only? It goes into battery at the same velocity regardless of fire mode. The only thing different in FA is the carrier trips the sear on it's way home. I'm not disputing, just asking. Thanks.

short barrels often have overdrilled gas ports to make up for the lack of dwell time between the gas port and the muzzle.

this "overgassing" results in a faster velocity cycle, resulting in the lighter buffer allowing a faster rebound off the back of the stock tube, thus a faster carrier closing velocity.

so the carrier bounces back off the extension unlocking the bolt just enough to reduce the firing pin hit.

[ungawa]

short barrels often have overdrilled gas ports to make up for the lack of dwell time between the gas port and the muzzle.

this "overgassing" results in a faster velocity cycle, resulting in the lighter buffer allowing a faster rebound off the back of the stock tube, thus a faster carrier closing velocity.

so the carrier bounces back off the extension unlocking the bolt just enough to reduce the firing pin hit.

I caught that with your last post. Maybe I wasn't clear, but I still don't understand why that would make a differnce in FA vs. SA with the same rifle.