Need some help with ar15 upper....

[azngunslngr11]

Sorry for the confusion in the thread. It is a 10.5" barrel. The distance from the gas port to the muzzle was an estimate, not an exact. I was responding and did not have my rifle with me, so it was a guess. The faxon barrel previously mentioned is on a different build. The barrel is dimpled, but found out the barrel is not a quality barrel, so I believe this is where the issues is.

 

[azngunslngr11]

Dwell time looks to be about just over 2.25". Barrel length is 10.5. Sorry for the confusion before with the 11.5"post.

Barrel is a 5.56 nato barrel. Problem with .223 PMC Bronze ammo, issues with x193 (any brand) seems to work alright, but still not 100% reliable. Variety of mags used. Surplus GI, magpul, C-products, IMI, even cheap Plinkster mags have worked.

Gas block is aligned, dimple lines up with rear set screw. I did clean some carbon build up right where the gas tube goes Into the gas block...could it be bleeding out from the block?

 

[azngunslngr11]

Forgot to add. PMC bronze is one of the least powered brass offerings you can get. Have you tried the ammo in another known reliable AR to verify you haven’t gotten a bad batch of ammo?

Again, hard to tell given the lack of details, especially when so many have thrown out under sized port but likely do not even know what it should be to start with.

Sorry for the lack of details. I just don't know how much is too much, and what is vs isn't helpful info. Thanks for the help and suggestions though. I did post some pictures.

 

[Plinker66]

Did you roll pin the gas tube into the gas block?

 

[azngunslngr11]

Gas tube was installed into the gas block by a gunsmith at a local gun store. Roll pin is nice and tight. I Inspected the block port alignment with the tube before installing into the barrel.

 

[jeep78]

Have you measured your gasport in your barrel?

 

[Wallace's]

I see you are in Cobb. If you could run it up to Bartow sans the FA lower, I could inspect it and try to determine root cause. A leaky gas block normally shows carbon blown out the sides, it would have to be super leaky though as carbon normally seals up minor imperfections quite quickly.

Also, Magpul MBUS are not rated for gas block mounting, especially on a select fire lower.

 

[azngunslngr11]

I see you are in Cobb. If you could run it up to Bartow sans the FA lower, I could inspect it and try to determine root cause. A leaky gas block normally shows carbon blown out the sides, it would have to be super leaky though as carbon normally seals up minor imperfections quite quickly.

Also, Magpul MBUS are not rated for gas block mounting, especially on a select fire lower.

Yeah! I will definitely try to get up that way. Thanks for offering up the help! Also, thanks for the heads up on the BUIS. I will move it rearward back to the free float.

 

[Radar363]

Bump for an update/resolution....

Also, I didn't want to be that guy but I have to ask: I understand that you wanted a spare upper but is there a reason you chose to build this upper using those parts rather than just buying a reliable factory upper from Colt or BCM?

 

[azngunslngr11]

Bump for an update/resolution....

Also, I didn't want to be that guy but I have to ask: I understand that you wanted a spare upper but is there a reason you chose to build this upper using those parts rather than just buying a reliable factory upper from Colt or BCM?

Sorry for the lack of responses on this thread, I personally have not had time yet with the holidays to test it out again. The reason another upper was built was to keep the wear and tear on the original Colt SP1 in the best condition. The SP1 was only factory fired, and I wanted to keep it original in the event that i would like to sell the rifle as a whole sometime in the future.

I should be taking it out next week (After Christmas) when I get some time off.