Ar pistol issue

[rfairman]

Hello all I'm fairly new to the forum and would like to pick a few of your brains if I may.

I just finished an ar pistol build and finally got to shoot it yesterday and it won't load the next round. I'm having to charge it every time. I'm using factory American Eagle 55gr fmj. I've ruled out magazines as they work fine in my 16" rifle. I also tried running a mag of speer gold dots through it and it cycled fine. Again the target ammo worked fine in my 16" ar.

I'm running a 10.5 barrel with pistol length gas system and a standard carbine buffer and spring. I'm thinking the problem is with the buffer.

Any help would be great thank you

[Onyx Z]

What buffer weight? Is the ammo 5.56 or 223? What brand barrel?

Need more details to diagnose. But I would tend to guess you need a lighter buffer. 10.5's can be tricky...

[rfairman]

I'm not sure on the buffer weight. The ammo was 223. The barrel is a blackhole weaponry barrel. I have another buffer I'll have to check the weight difference.

[MistWolf]

Your AR is not getting enough gas to operate the action. Potential problems include blockage anywhere in the gas system, mis-aligned gas block, leaky gas block, leaky gas key, leaky gas rings or a gas port that's too small in diameter. In the "What the Heck" department would include, gas tube that's too short or missing, missing gas rings or a non-existent gas port

[rfairman]

I've checked the gas key and rings for leaks and there are none. I will check the gas block alignment tomorrow morning at work. How large should the gas port be?
Also I can see that my gas block is not leaking

[HeavyDuty]

Is it ejecting the fired cases? Your post isn't clear about that.

[rfairman]

Most of the time yes it's ejecting the fired cases. It just seems like the bcg is not moving backwards far enough to load the next round

[Captiva]

MistWolf, you can tell by the issue that the buffer is irrelevant to this problem? TIA

[rfairman]

So I'm going to try my T2 buffer this weekend. I'm also still going to look at the gas block and port. I'm going to drill the port with a 5/64 drill bit and check the alignment of the gas block.

The buffer weights are 0.15 lb for the standard and 0.25 for the t2. (My scale at work doesn't do ounces)

[MistWolf]

MistWolf, you can tell by the issue that the buffer is irrelevant to this problem? TIA

The problem as originally described sounded as if the AR wasn't extracting or ejecting. It takes more than an overweight buffer to cause short stroking to that degree.

rfairman has clarified that the rifle is extracting and ejecting without picking up the next round or having a bolt over. That is in that grey zone where the problem could be a lack of lubrication, not enough gas or an overweight buffer. First thing I do when encountering this problem is to lube the BCG, making sure a few drops are put in the carrier vents and the bolt where it sticks out of the carrier. I would also look at the buffer to see which is installed in the AR. If it's an H2 or H3 and still short strokes after lubing, it's time to try a lighter buffer. If it's a carbine or maybe an H buffer, and short strokes after lubing, it's time to go through the gas system