SBR /Pistol Short Stroking

Mon Jul 23, 2018 4:28 am

So I have bought the 12 inch upper from Atlantic and built "Pistol" first range, running mostly Winchester white box. 2 or 3 rounds out of every mag would short stroke. (eject but not pick up the next round.) Thelower was running the SBPD brace with the buffer and spring that came with the Brace. Since the trip to the range I have installed a Wolf reduce power Buffer Spring which I hope resolves this . Anyone else running a similar set up run into Short Stroking?

e292644 · Mon Jul 23, 2018 4:40 am

Seems to me it's under-gassed. You may need to open it a little bit.
See reference HERE

Mon Jul 23, 2018 12:36 pm

Shoot some more. Brush the chamber thoroughly. Probably a couple hundred rounds may free it up a bit. Don't open the gas port right away, you can't undo that.

Mon Jul 23, 2018 1:37 pm

Qwerty wrote: ↑Mon Jul 23, 2018 12:36 pm Shoot some more. Brush the chamber thoroughly. Probably a couple hundred rounds may free it up a bit. Don't open the gas port right away, you can't undo that.

The pistol I did has an 11.5 inch barrel. This was at least a year before the 12 and 12.5 inch uppers were available. I have a 12 inch version and only around 200 of those came in. The rest are 12.5.
It was in fact made from a 16 inch upper with the heavier barrel profile. The GP on those are much to small to cycle the shorter barreled action. It was necessary to open it up and as a matter of fact it is because of this gun and conversations with Steve from wolf that the 12 and 12.5 inch uppers came about. They settled on the GP on those at being at 0.095. Several hundred FP brass rounds must be used to get those to seat and function 100%. I used IMI 855.
Tula ammo has proven to be the most unreliable even after break in.

Tue Jul 24, 2018 7:28 am

Thanks for the feed back guys ,in looking at some of the brass , I am seeing some scratching so along with the breaking in , I am going to hone the chamber ( I usually this with my ARs any way)

Fri Jul 27, 2018 1:34 pm

First, thank you guys for feed back. I made 3 changes and the result is that it is now running Wolf 223 55 grain Winchester whitebox M193 and Aguila 55 grain 223 reliably .
The changes were swapping in a Wolf Reduced power buffer spring and Lightly honing the chamber (Always lots of Lube) . These 2 changes resulted in eliminating short stroking. Lastly I swapped the Muzzle device (You Purists please forgive me) to a A2 Birdcage so that I can Run My Gemtech Halo it. I am falling in love with this ugly little Mut of a gun.

crafts.jpg

Mon Jul 30, 2018 5:54 am

That looks badass!

JP

Thu Aug 09, 2018 9:37 pm

maybe with that can you can use the stronger spring.
pls share what hone you used.
useful info for the benefit of others.
thanks.

Sat Aug 11, 2018 3:37 pm

Well , as it happens a buddy had "borrowed" my Flex hone , so I went full "Jethro" went over to to Runnings grabbed a 45, caliber brush , then stopped at Autozone and grabbed a tube of fine Valve Lapping compound. attached the brush to a length of cleaning rod put the rod in the chuck of a cordless drill. Put a little bit of lapping compound on the brush, push it into the chamber and run the drill lightly
.