SBR Build

[STIGUY]

Contemplating an SBR with either an 10 or 12" barrel. Would be loping off an existing stainless barrel. For reliability and functioning, I will be using one of those after market piston kits and was wondering other than looks, does barrel length matter with these kits. Before, someone comments, I know.....the paperwork and $200 stamp.

I just would like one PDW.....even though nit select fire....like all the cool kids?

[flip4179]

I've got a 12.5" SBR on the back burner right now. I went with 12.5 because there is a little more accuracy and better ballistics than with the 10". YMMV. When I mean ballistics, I mean the ability of the bullet to frag under 100 yards. I will be running a can on mine also with a Noveske switch block. As far as piston goes, it should run just fine chopped down.

[G-ManBart]

I don't have a whole bunch of experience with the shorter barrels (my duty rifle has a 14.5" barrel on it and runs like a top), but several buddies have 9" versions, and they say that they can be a little finnicky. For example, one buddy can't get his to run with standard mags, but with PMags it's 100%...strange as that may sound. R,

[Beretta Lover]

I have a 11.5. Colt commando upper with a welded on long flash hider to make it legal. I think anytime you decrease barrel lenght below 14.5 dwell time can be a potential issue. My gun runs well with brass cased ammo and has some failures to extract with steel cased ammo. Im going to run a crane o ring and spring under my extractor too see if it helps. I have seen some SF types running 7 and 10 inch guns fwiw

[caspian guy]

I have a 7.5" upper I just shot for the first time today (on a pistol lower). I built it with an Adams Arms piston kit and a flaming pig muzzle device. It ran the first 80ish rounds of Hornady Training ammo (steel cased version of their tap ammo) with no drama... Tried it with the gas block set to the wide open position, and in the supressed position (reduces the gas some) both worked. Not a long term test I know but I was impressed with how well it worked in a barrel length that is hard to make work normaly. I'll be curious to see how it works long term...

Short uppers may be a good niche for these piston things.

Edited November 21, 2010 by caspian guy

[smokshwn]

If you buy a reputable barrel in any of the lengths mentioned you should have a system that runs well as the gas port should be drilled commensurate with the dwell time/barrel length.

On another note if you plan on running a suppressor make sure you check with the manufacturers of the suppressors you are considering. Some will have restrictions on barrel length and suppressor warranty due to the potential for baffle strikes or overpressurization of the can (down in the 7-9" range).

[Wakal]

So far, I've built 7.5", 10", 12", and 14.5" uppers for my family of SBR's (all standard gas systems). The 7.5" needed a pigtail gas tube plus the port opened to run consistently. The others all ran fine as issued. I run a can on the 12" gun (standard gas with a Gasbuster charging handle), one of the 14.5" guns (Adams Arms piston system), and a POF 18" upper. All work fine.

The can on the 7.5" gun was a bit...abrupt. As in "I abruptly stopped shooting it because there was hot gas and powder residue in my eyes, oh damn, oh damn" (or words to that effect). Even with the Gasbuster it was annoying. On the standard gas 12", no problems at all.

Alex

[caspian guy]

So far, I've built 7.5", 10", 12", and 14.5" uppers for my family of SBR's (all standard gas systems). The 7.5" needed a pigtail gas tube plus the port opened to run consistently. The others all ran fine as issued. I run a can on the 12" gun (standard gas with a Gasbuster charging handle), one of the 14.5" guns (Adams Arms piston system), and a POF 18" upper. All work fine.

The can on the 7.5" gun was a bit...abrupt. As in "I abruptly stopped shooting it because there was hot gas and powder residue in my eyes, oh damn, oh damn" (or words to that effect). Even with the Gasbuster it was annoying. On the standard gas 12", no problems at all.

Alex

Hmm... Good to know... I wonder if the piston setup on the 7.5" upper will help with the gas in the face effect from a suppressor... I have never shot a supressor on an upper this short.

[EkuJustice]

Beretta Lover, the oring is a good fix for the problem. What buffer are you running in the gun. Mine would work with a carbine but runs much smoother with the spikes tactical H2. I put the oring under the extractor on all my guns. My 10.5 inch will shoot anything I have shoved in it. Gets quite a bit of wolf and spits it right out.

[dbltapipsc]

A 7" piston gun with a suppressor on it will not blast you with gas. If your piston setup is set on suppressed at the gas key, no issues. I have run suppressed from 7-16" both select fire and semi without issues. The shorter gas guns do give you a little taste in the mouth after shooting suppressed for a bit. Also, I have had a 7" gun get 5/8 groups at 100 yards. So accuracy with a smaller gun is a non issue. Terminal ballistics is, but thats another day. However shorter barrells do void certain warranties as smokshwn said. I work on both gas/piston guns and use them daily. Either platform is acceptable if setup correctly.

[Beretta Lover]

Beretta Lover, the oring is a good fix for the problem. What buffer are you running in the gun. Mine would work with a carbine but runs much smoother with the spikes tactical H2. I put the oring under the extractor on all my guns. My 10.5 inch will shoot anything I have shoved in it. Gets quite a bit of wolf and spits it right out.

I run a DPMS I think, H buffer. I have not tried my gun with live ammo since installing the o ring but I have had luck with them before