DPMS AR-10 Gas Block Question

[AManWearingAHat]

I want to swap a gas block on an old school DPMS AP4 AR-10. It's currently wearing a standard front sight tower, Id like to replace it with a low profile gas block to facilitate a longer free float tube.

Removal of the old base should not be a problem however the low pro block I'd like to use is of the set screw variety. Will I need to dimple the barrel to better accommodate the set screws? If so what is the best procedure for dimpling? I was thinking of just using the nose of an appropriately sized drill bit via match drilling with the block installed using the non-working hole screws to hold the block in place. Before I did anything I wanted to seek advice here first. Thanks.

 

[Bigtrucknut]

I have not dimpled any of the barrels on my ARs for the set screw gas blocks i'm using. You could buy a dimple drill fixture to do it right - they index off the gas port to ensure the dimples are drilled correctly. Unless you have the drilling fixture I suggest you don't worry about drilling your barrel - if you miss drill it the set screw will always align on that fucked up dimple.

 

[bobke]

Have used the SLR dimpling jig for SLR adj gas blocks, but would advise if not using an SLR block to confirm location of GB holes so distance off shoulder is consistent with jig pattern. Some sit up tight to shoulder, others may sit .030-.035 off same. Measure twice, drill once. Wilson Combat and some others mill a flat 180d to port to simplify this process.

 

[Bigtrucknut]

I have not dimpled any of the barrels on my ARs for the set screw gas blocks I'm using. You could buy a dimple drill fixture to do it right - they index off the gas port to ensure the dimples are drilled correctly. Unless you have the drilling fixture I suggest you don't worry about drilling your barrel - if you miss drill it the set screw will always align on that fucked up dimple.

Funny thing is that I have the SLR dimpling jig for a .875" gas block and never used it on the one barrel I have with an .875" gas block. Never got one for the .750" barrels.

 

[MNhunter1]

Highly recommend an adjustable block if you are swapping it out. I'm of the belief that no large frame AR should be without one. They are so much more sensitive than their small frame brothers. You will also likely run into barrel coating variances under the A2 block as the coatings are sometimes applied after the A2 block was pinned in place. A low profile block will also not completely cover the void and pin holes from the A2 block. I believe Larue has an extended low profile block, but not an adjustable one. One other option, if you choose to stick with a non-adjustable block, is to cut down your pinned A2 block to fit under an extended rail - cheapest option and maintains the pinned block.

 

[AManWearingAHat]

I hadn't thought of cutting the old block, that doesn't seem like a terrible idea in this case as the gun is known to run well with the stock Block / FSB. The results I saw on google don't even look like hack jobs if they're done with some care.

 

[nutation]

You can skip dimpling. The set screws will bite into the barrel a bit under even modest (~ 20 inch-pounds) torque.