fte issues with heavy ammo

[rugerceltics13]

so i've built a standard carbine 16 inch 300 bo ar that fte every single time using s&b, magtech, remington umc around120 grain. if i go lighter with barnes or hornady 110 it only does it every 9-10 rounds. i've got the gas block all the way open but still it won't eject anything heavier than 110. before i opened up the gb, it was having fte issues with the lighter grains too. but once i adjusted it, less ftes per mag. have yet to get it to run a full mag without any fte issues. standard weigh buffer, carbine tube, carbine gas, seekins adj gb. what else should i be looking for?

 

[Allsmiles]

It sounds like a low gas issue. Double check your gas block and make sure it is aligned correctly with the gas vent in the barrel. If you have another AR, swap lowers just to rule out anything out of spec. If you duplicate the FTE with another lower, upper is issue. If it runs with a different lower; something most likely is off in the buffer tube/spring/buffer on your build.

 

[N.Ga.Trader]

It sounds like a low gas issue. Double check your gas block and make sure it is aligned correctly with the gas vent in the barrel. If you have another AR, swap lowers just to rule out anything out of spec. If you duplicate the FTE with another lower, upper is issue. If it runs with a different lower; something most likely is off in the buffer tube/spring/buffer on your build.

That would be my first guess as well.

Sent from my LGL84VL using Tapatalk

 

[Dirty J]

Yeah. You should really never need to have an adj gas block "all the way open".

 

[rugerceltics13]

It sounds like a low gas issue. Double check your gas block and make sure it is aligned correctly with the gas vent in the barrel. If you have another AR, swap lowers just to rule out anything out of spec. If you duplicate the FTE with another lower, upper is issue. If it runs with a different lower; something most likely is off in the buffer tube/spring/buffer on your build.

swapped with 2 other lowers. still having issues. one of the lowers i run a jp silent capture spring. and it seems to have fewer issues. but they still persist

 

[rugerceltics13]

Yeah. You should really never need to have an adj gas block "all the way open".

i found that the more i opened it, the fewer issues i had

 

[Lionheart]

Good luck. I had issues with different bullet weights also using an adjustable gas block.
I finally got pistol gas and .300 Blckout mags...made it a dedicated suppressed gun shooting 220 subs.
Works fine now.

 

[Allsmiles]

Since it wouldn't work with different lowers, issue is in upper. Things to check out. Remove gas block and tube. Make sure tube isn't blocked with debris and turned correct way in gas block. Check gas block and make sure gas post is on correctly drilled. Hole should be under rear screw. Lastly, make sure you are lining up the agb correctly when installing it. Have you tried to run it suppressed? That is an easy way to identify low gas if it runs correctly.

 

[Plinker66]

You’ve got to line the gas block up both ways on the barrel. Usually there is a gap between the block and the ledge on the barrel. You can’t just push the block against the ledge. If you have the block up against the ledge it’s prolly off.

 

[jeep78]

You need pistol gas tube for 300BO. A fix for a carbine gas tube is the 300BO buffer spring sold by Brownells and others if you do not want to drill out your gas port.

Those springs are made just for your setup. And get some 300bo mags, they do make a difference.