So I currently have a DPMS AP4.
I decided to make it a long range rifle, and bought a 24" AR10T barrel at a really good price.
It needs a .875 Gas block, and I am having a hard time finding a quality gas block that size. Recomendations?
Secondly, I am not sure what size gas tube to get for it. I know the Armalite's have a slightly longer gas tube, but
I am using a DPMS rifle with the Armalite barrel. Regular length gas tube or the Armalite length?
PRI makes a .875" low profile gas block, as does Larue Tactical. Armalite's railed gas blocks are also available in .875.
Use Armalite barrel parts with an Armalite barrel, so you'd want the Armalite gas tube.
Badger 0.875" Gas Block
You need an Armalite gas tube.
You also should use a complete AR10 bolt carrier group.
I also recommend using an Armalite buffer spring. Your buffer will depend on the type of buttstock you are going to use.
If you decide to shorten your ar10T barrel down to 20", you will need to open the gas port up to 0.086" (#44 wire guage drill bit).
Oh...Important. If you are running original DPMS mags, you will need the new AR10 bolt catch to properly lock back the bolt on the last round.
If you use C Products mags, you can use the standard AR15 bolt catch.
If you do all that, you should not have any problems.
Hope this helps.
btw - i have built 2 dpms rifles so far with AR10 barrels. Both times, the barrels were extremely tight fitting into the upper receivers. 2 data points do not make a trend...