Here's the story. I've have a customized 16" Evolution barrel, that I love dearly. It of course came with a short gas system. I now want to convert that rifle to use a full length one piece Carbon Fiber free float tube from Clark Custom. I can't install a long one piece hand guard and then install the short gas system under it. (Maybe if I was really, really small:))

So the only option I see is to weld up the gas hole in the barrel and drill a new one at the std. 20"+ barrel location. The biggest problem is the front half of the barrel is .730" and I can only find gas blocks in .750". I would like to use Bushmaster's gas block with the weaver on 3 sides, but it's .750". Another problem is I don't know EXACTLY where to drill it, I am a machinist but I just don't know the location. And I don't know what diameter to drill it for a 16" barrel with a long gas tube.

I'm open to any suggestions.

Kevin

RRA (Rock River Arms) has mid-length handguards.  The front sight is NOT the gas block.  They have a small gas block hidden under the handguards.  I don't know how small it would need to be on your setup but this might be worth looking into. The Dissipator (Bushmaster) does the same thing now that I think about it.  I believe the reason for the small gas block at the short position (rather than using the sight base) is that it will not cycle the action with such a short distance after the gas block.

www.bushmaster.com/shopping/barrel-assemblies/pbbl-16dm4a.asp

EDITED:  Oh yeah, welcome to the board

Quoted: RRA (Rock River Arms) has mid-length handguards.  The front sight is NOT the gas block.  They have a small gas block hidden under the handguards.  I don't know how small it would need to be on your setup but this might be worth looking into. The Dissipator (Bushmaster) does the same thing now that I think about it.  I believe the reason for the small gas block at the short position (rather than using the sight base) is that it will not cycle the action with such a short distance after the gas block.

Are you sure the RR has a second block under the handgaurds? My Armalite mid-length does not. It works fine. This gas port location is actually more appropriate on a 16 inch barrel. It is in a very similalr location from the muzzle compared to a 20 inch rifle.

The very short "CAR" gas system is better suited to the 11.5 inch barrel.

Quoted: Quoted: RRA (Rock River Arms) has mid-length handguards.  The front sight is NOT the gas block.  They have a small gas block hidden under the handguards.  I don't know how small it would need to be on your setup but this might be worth looking into. The Dissipator (Bushmaster) does the same thing now that I think about it.  I believe the reason for the small gas block at the short position (rather than using the sight base) is that it will not cycle the action with such a short distance after the gas block. Are you sure the RR has a second block under the handgaurds? My Armalite mid-length does not. It works fine. This gas port location is actually more appropriate on a 16 inch barrel. It is in a very similalr location from the muzzle compared to a 20 inch rifle. The very short "CAR" gas system is better suited to the 11.5 inch barrel.

I was going on posts here, not personal experience, so I could be wrong about the RRA mid-length setup.  I thought the gas block was in the normal 16" bbl location for these (similar to the Dissipator).  Again, could be wrong...  
The Dissipator shows what I am talking about though, with the small gas block under the handguards in the normal spot and a front sight mounted in front of the handguards.

The "very short" gas system doesn't come into play here at all and I must have been unclear - I never meant to refer to that setup.

I already have a low profile gas block that will fit under the hand guard. The problem is the the hand guard is one peice, as in the barrel nut is part of the tube. So once I thread it onto the upper I can't install the gas block cause I can't get to it.

Kevin

Wes,
Just looked on your site and I like the PRI a lot but it's more $$ than I wanted to spend. I don't really need all the little do-dad's to hang off it. Does anyone make a 2pc simple carbon fiber, or fiberglass? I may turn this one I have into a 2pc.

Kevin

Wes,
The ArmaLite is perfect, that's what I need. Do you sell those? I don't see them on your site. Is direct from ArmaLite the only place to get those?

Kevin

I can help i think,get a cmore rail from BM or fulton armory, the handgaurd screws onto the part that is mounted to upper,says to locktite with red,but you could do blue or not at all so you can get to block. That will help and its cheaper than some others. i got mine for m4 and was on sale9knocked 50.00 off) at fultons.I had a disapator and know what you are talking about. Thats my best opinion.