Problem with adjustable gas block

[lawdog]

I built a DPMS 260Rem upper with the following items: a Fulton Armory upper receiver, a Daniel Defense 12.0 Lite Rail, a DPMS 24" 260 Rem barrel with a 1-8.5 twist (rifle length gas tube)and a JP adjustable gas block. This upper sits on a DPMS lower reciver. The JP gas block does not match up with the barrel's gas port as it hits the DD rail. I had to use a Micro gas block and the gas block actually fits about 1/32" to 1/16" under the DD rail.

I believe I have three options here, so please chime if you have another suggestion. 1). "Mill" the back of the JP gas block so it fits under the DD rail. 2). "Mill" the DD rail. Ouch! or 3). Replace the barrel. I know the rail and gas block are GTG as I have a 308 upper and have a DD rail on that and the JP fits fine on that without any problems. I would prefer not to change the barrel as I am getting some outstanding groups with it. Any suggestions, advice or recommendations would be greatly appreciated. Thanks again. LD.

 

[Powder_Burns]

Re: Problem with adjustable gas block

Why do you need adjustable gas? DD has a low profile gas block tailored to their rail system. There are adjustable flow gas tubes as well..you have options here.

 

[lawdog]

Re: Problem with adjustable gas block

I have a bull barrel (.936" diameter, I think), so there aren't too many adjustable gas blocks out there for them. I think my rifle suffers from "overgassing" so I'm trying to control it so that it isn't so harsh on my brass. I hope to get a suppressor in the not so near future and have read that adjustable gas blocks help with their performance.

 

[Hellbender]

Re: Problem with adjustable gas block

If the same rail and gas block fits on the one gun, but does not fit on the other, something has to be different somewhere.

Everything is the same on the 2 guns except the caliber???

 

[lawdog]

Re: Problem with adjustable gas block

The only thing that comes to mind is that the 260 barrel was somehow "cut" wrong. The lip on the barrel that prevents the gas block from sliding back towards the receiver is closer to the receiver than it should be. The micro gas block works just fine but you can definitely see where it goes under the DD rail. Probably more frustrating than anything else. Both DD rails are teh exact same length. The only difference in teh barrels besides the caliber is their respective lengths. The 308 is 20" with a rifle length gas tube and the 260 is a 24" fluted barrel with a full length rifle gas tube. But that shouldn't make a difference.

 

[Hellbender]

Re: Problem with adjustable gas block

Sounds like one of two things.

1. You have an Armalite AR10 (instead of DPMS) cut barrel, they have a .2" (approx.) different gas tube location.....

2. Are you sure the HOLE location is wrong, or just the shoulder that the block is hitting?

You have to have the proper amount of tube extending into the receiver, not just the holes lining up on the barrel. Armalite uses a longer gas tube.

 

[lawdog]

Re: Problem with adjustable gas block

HB,

The barrel is marked DPMS. The shoulder and the gas port locations are both wrong. The rifle would not extract a spent round when I used the adjustable gas block, even when it was opened all the way. When I use the micro gas block, everything lines up, under the rail of course, and the rifle functions just fine. Thanks for the input. I think you are right about the barrel being cut for an AR10 setup, but marked DPMS. I have put together various builds and have never encountered this problem. I guess you learn something new everyday. Thanks for the input and I'll look for the specs on both types of barrels for future reference.

 

[Rovieairto]

Re: Problem with adjustable gas block

One thing you could always do it to purposely "miss-align" the micro gas block by a measured amount as a means of regulating the gas flow.
This will work.

 

[The King]

Re: Problem with adjustable gas block

I don't think they make a .936 adjustable low profile...not that I have seen.

 

[Bighouse]

Re: Problem with adjustable gas block

Have you looked at the Paladin Machine block? It may fit your needs. I have one on my RRA LAR-8 Varmint project. I have not fired it yet so no range report but everyone I found online running it was happy with it.