not cycling

[georgeib]

Honestly even if you pushed the gas block all the way up against the shoulder, the orifice in the block itself is generous enough for this not to matter. My tendency is to look at two areas to start off with. First make sure that the gas block is centered over the gas port laterally, and second make sure that nothing is blocking the gas key on the carrier by pushing a piece of trimmer line down the gas key until it appears inside the carrier bore.

Then I would try to make sure that the gas key is properly fastened to the carrier. If you have an inch pounds torque wrench, set it to 40 inch pounds and try to tighten the gas key screws. Then set it to 30 inch lbs and try to loosen them. If the screws move, you've likely got a broken screw.

ETA: If you don't have a bore scope, and don't feel like ordering one, you can check gas block to port alignment by removing the gas block, marking a couple pencil lines on the barrel inline with either edge of the gas port, and then lining up the gas block laterally using those lines. The longitudinal alignment can be verified with a caliper. Measure the distance inside the gas block from the rear most portion of the gas orifice, and then on the barrel measure the distance from the rear edge of the gas block to the barrel shoulder.

ETA2: Does the barrel have a dimple at the bottom for the gas block screw?

[hoopharted]

Honestly even if you pushed the gas block all the way up against the shoulder, the orifice in the block itself is generous enough for this not to matter. My tendency is to look at two areas to start off with. First make sure that the gas block is centered over the gas port laterally, and second make sure that nothing is blocking the gas key on the carrier by pushing a piece of trimmer line down the gas key until it appears inside the carrier bore.

Then I would try to make sure that the gas key is properly fastened to the carrier. If you have an inch pounds torque wrench, set it to 40 inch pounds and try to tighten the gas key screws. Then set it to 30 inch lbs and try to loosen them. If the screws move, you've likely got a broken screw.

ETA: If you don't have a bore scope, and don't feel like ordering one, you can check gas block to port alignment by removing the gas block, marking a couple pencil lines on the barrel inline with either edge of the gas port, and then lining up the gas block laterally using those lines. The longitudinal alignment can be verified with a caliper. Measure the distance inside the gas block from the rear most portion of the gas orifice, and then on the barrel measure the distance from the rear edge of the gas block to the barrel shoulder.

ETA2: Does the barrel have a dimple at the bottom for the gas block screw?

it did not have dimples , it has two set screws , i will pull the GB and align with the pencil marks , and back it off the shoulder a tad

[titsonritz]

it did not have dimples , it has two set screws , i will pull the GB and align with the pencil marks , and back it off the shoulder a tad

Don't Be An Uncle Cletus, Dimple Your Damn Barrel...

[1168]

it tried to cycle once , i put maybe 30 rds through it

Make sure you turned the adjustment screw on the gas block in the right direction, and check the gas key screws, clockwise. If one is broken, it’ll spin.

Its pretty hard to misalign a gas block that badly. It sounds more like you have a leak, to me. I’d prolly still check the alignment, though, if the other two things are right.

[georgeib]

it did not have dimples , it has two set screws , i will pull the GB and align with the pencil marks , and back it off the shoulder a tad

For troubleshooting purposes, do you have a standard gas block you can temporarily swap in?

[hoopharted]

For troubleshooting purposes, do you have a standard gas block you can temporarily swap in?

i do not

[georgeib]

i do not

I don't think the gas block is the issue, but it very well could be. Once you've checked the other suggestions, it may behoove you to pull a non-adjustable gas block off another rifle and try it. I don't think you'll need to do that, but it's something to keep in mind.

[DG23]

Honestly even if you pushed the gas block all the way up against the shoulder, the orifice in the block itself is generous enough for this not to matter.

Yup.

That hand guard retainer is not very thick.

[georgeib]

Yup.

That hand guard retainer is not very thick.

I did that with my first build, not knowing any better, and when I later pulled the gas block, I could see the carbon ring in the shape of the gas block's orifice on the barrel. It didn't occlude the gas port at all.

[HKGuns]

Make sure you turned the adjustment screw on the gas block in the right direction, and check the gas key screws, clockwise. If one is broken, it’ll spin.

Its pretty hard to misalign a gas block that badly. It sounds more like you have a leak, to me. I’d prolly still check the alignment, though, if the other two things are right.

While I don’t disagree, I think you start at the gas block, especially if the barrel wasn’t dimpled.

My next step would be to check the gas key for leaks, however, on a first build, how likely is that actually?