View Full Version : AR Pistol - Please look at the pictures of my brass

09-06-2012, 9:53 PM
I have an AR Pistol, barrel length of 7.5in. Below is an attempt to capture what my extractor is doing to the brass rim of the cartridge upon ejection. Most of the time I am getting positive extraction and ejection at about the 3-3:30 position with the occasional dribble out of the ejection port.

Quick stats:
7.5 Upper
Spikes ST-T2 buffer
Lowe's O-ring around the extractor spring (I have a BCM extractor upgrade kit coming)


Edit: I bought a H3 buffer from Palmetto State Armory and it seems to have slowed the bolt down. Seems to have cleared up my issue. Thanks guys

09-06-2012, 10:37 PM
I have limited experience with AR pistols

It lools like your timing is off and the extractor is trying to pull the brass too early in the cycle

The piston drive sustem works well in sbr and pistols as the bolt carrier is not tipped upwards during cycling

What gas tube are you running? Is it straight or does it have a loop to slow the cycling?

With the double feed, it could be a bounce of the bolt carrier. Is the spykes buffer designed for pistols?

09-06-2012, 10:43 PM
Possibly over gassed. The occasional dribble is probably the case ripping off before full ejection.

Try out an adjustable gas block. I did and my 7.5" pistol shoots softer than any other ar pistol I've shot including piston driven ones. ( I did lighten the standard buffer as well )

09-06-2012, 10:51 PM

I added the link not to send you off to buy an overpriced item, but to read the description on the pigtail gas system

09-07-2012, 4:09 AM
The shorter gas system causes the gas to be at a higher pressure when it hits the gas tube, plus the cartidge is not fully depressurized when the bolt it trying to yank it out. The AR was not really meant to have such a short barrel or a shorter gas system. You should have gotten the Sig 556 pistol.

09-07-2012, 4:31 AM
I would take the o-ring off and try it again.
Did you have an extraction problem and then added the o-ring on the extractor?
I have seen that mod be pretty hard on brass.

Take care,

09-07-2012, 6:08 AM

My pistol is set up with the same barrel length and ST buffer. Would also like to know if you can try without the o-ring and see how that affects cycling.