I bought a Fulton Armory upper for a DPMS 260Rem. build.  It has a DD Lite Rail 12.0 and a DPMS 260Rem. bull barrel with a 1-8.5 twist.  I attempted to install a JP adjustable gas block, but the gas block won't go back far enough on the barrel as it hits the DD lite rail before the gas block can align with the gas port in the barrel.  It looks like the contour of the barrel was cut wrong.  My two options appear to be to either "mill" the back end of the gas block by about 1/32" or "mill" the front end of the Lite rail by 1/32". I have an identical set up on a 308LR and the gas block works on it just fine.  Any suggestions would be greatly appreciated.  The 260 currently has a micro gas block that works, but I am getting signs over overpressue when using factory ammo and would like to have an adjustable gas block on it.  Thanks.

Tag for outcome.

Don't have any input to your problem but this is Overpressure is an ammunition problem and does not have anything to do with the gas system..................

Unless maybe the gas port in the barrel is to big.

If it is jacked up that badly, I would trash the barrel.

Agreed ... the only reason I would use an adjustable GB would be if a suppressor was causing over-pressures not because my barrel was FUBAR.

To the OP:  What factory ammo are you referencing.  I found that all the Corbon loads resulted in excess port pressure on my DPMS 260.  I have not found any problems with any other ammo though.

...and I think an adjustable gas block is a perfectly appropriate way to deal with this issue.

As I was building my 260, I read multiple posts indicating that the 308 AR platform suffers from "overgassing"  and that adjustable gas blocks are a way to correct the problem.  I also wanted to someday get a suppressor for it, so I thought I could kill two birds with one stone.  I used a JP adjustable gas block when I sighted in my Vortex scope.  I did not catch the fact that the gas block was not directly over the gas port hole on the barrelI, as I did not encounter this problem when I built my 308.  I used Black Hiils Gold 260 Rem with the 139gr. Lapua Scenar bullet.  The primers looked a bit cratered and the brass was ejecting extremely hot. So hot, in fact, it melted a nylon brass catcher I was using as I save my brass.  I adjusted the block from all the way open to all the way closed and the bolt would not extract the spent casing so I had to manually charge the weapon after every shot.  I was perplexed until I took the rifle home and realized that the adjustable gas block was not aligned properly.  I switched to the micro gas block and I have not have any problems as far as the weapon ejecting the spent casings properly.  I have since fired more Black Hills ammo and the brass does not show any visible signs of overpressure.

I have started reloading using H4350 and 140gr. Amax. bullets.  The load is "light" compared to other loads I found, but I am getting exceptional accuracy out of it.  I thought that by using an adjustable gas block, I would also be able direct more gas away from the bolt carrier grouop and lower any possible overpressure due to a hot load.  This last part was an assumption on my part.  So there you have it. I appreciate everyone's comments and I have learned quite a bit from this experience.

I think I have solved my problem.  I drilled and tapped the top of my adj. gas block for a new adj. screw/bolt.  The gas port hole and the new adj. screw/bolt line up perfectly.  I closed off the original adj. screw and used Loctite to "seal" it in place. I will get to the range either today or tomorrow to see if it works. I will go ahead and order a new gas tube and replace the existing one as it now has two holes in it and don't want it to snap/break.