ar15 new build

Bigfuzzy · Jun 27, 2020

I am new to building ARs. Have no problem with lowers.(so far). my 2nd upper build will not complete the cycle. does all of the cycle except for the last 1/4 to 3/8 of an inch.
any idea as to the problem so i know what to look for? the lower runs fine with other uppers.

TheGriff · Jun 27, 2020

same ammo as other upper?
can you swap parts with the other upper: bcg, buffer and spring, both?

Bigfuzzy · Jun 28, 2020

have tried different ammo, bcg, I guess next will be checking gas block & removing barrel.

TheGriff · Jun 28, 2020

That makes sense if the gas block is partially the gas port in the barrel. I didn't think of that.
Did you swap out the spring and buffer from another working AR?

Bigfuzzy · Jun 28, 2020

are you talking about in the lower? I have changed the complete lower, same result

TheGriff · Jun 29, 2020

Sorry, I re-read the first post and realized you already tried that.

Bigfuzzy · Jun 30, 2020

thanks

rotarymike · Jul 1, 2020

make sure your gas block / barrel isn't slightly off level. That will slant the gas tube enough to place enough force on the gas tube/key interface to keep the bolt from going into battery.

Bigfuzzy · Jul 2, 2020

will check that 1st in the next few days, thanks

Imaduckin · Jul 8, 2020

Did you install an adjustable gas block, if so it probably needs adjusting

Imaduckin · Jul 8, 2020

Also be sure gas block was drilled properly, some of the bargain ones dont line up with the hole on barrel

Bigfuzzy · Jul 16, 2020

well problem resolved. yall did good.
it was in the gas system, tube was off to 1 side(bent I guess?) i need to do a better job checking on the next build.
had to sand the tube & repair the gas port on the bcg. all's well now, ran 2 mags thru it & all went well.

thanks again