Carbine length stock over pistol length gas system?

[TrickyNicky]

Aside from going free float, has any one seen this done with regular M4 furniture or MOE? Tried googling it and didn't see anything definitive. I'm wondering if heat off the block under the guard would be too much for the polymer, there is a heat shield though so I don't know. Also not sure if the pressure of the handguard itself would be enough to keep the little doohickey that holds it together snug against the sight, or does that doohickey need to be sandwiched between the sight and the part of the barrel it usually rests against?

I think I can make it work by having a barrel turned with a .0936 diameter at the block and a smaller diameter doohickey stop at the appropriate length. I haven't ruled out the possibility of a custom barrel either way so its just more food for thought.

[Dolomite_supafly]

Most .750" clamp on gas blocks will clamp down onto the barrel as long as it is spec at .740.

I have done exactly what you want to do. Get a clamp on, not setscrew, type gas block. Install a portion of a gas tube to hold the hand guard end cap in place. You might have to add a spacer between the barrel and hand guard end cap to keep it from rattling around.

As far as the heat I would not worry about it. The gas block won't be that much hotter than the barrel. It will be closer but unless you are doing mag dumps I would not worry about it.

When I installed mine I put the hand guards into the delta ring. The I pushed back on the gas block until it stopped then I clamped it in place. Again, I had to use something to take up the .010" difference between the .750" hand guard end cap and the .740" barrel.

[TMF]

I'm confused. Wouldn't a carbine length handguard extend past the gas block on a pistol length gas system? Seems to me the choice would be a FF handguard/rail at carbine length would fit over the gas block and expose a little bit of the barrel. Or maybe I'm just not understanding the question right. Sent from my iPad using Tapatalk

[TrickyNicky]

I think you mostly get it TMF, there will be two gas blocks on this rifle, one low profile under the handguard, and another acting as a sight further up the barrel to use as a sight. Also might help clear things up to know this is going to be a 16" barrel.

The whole point is that I want to build an "evil twin" in 300 blk that matches my favorite ar only with FDE furniture instead of black. Then I'll get FDE mags or maybe just paint some that I've already got, then I'll have color coordinated weaponry :rolleyes:

Thanks a bunch Dolomite, now comes the fun part, emailing vendors to make sure there will be compatability. Still haven't ruled out having a barrel made by Ron Williams, seems his work is pretty popular.

[Dolomite_supafly]

Want to hear something really funky. About a decade ago there was a custom AR builder that would install two functioning gas blocks. He would install one at the pistol position and one at the carbine position. The pistol position would have a very small port and the carbine position would have a normal port. He claimed it helped with recoil as well as reliability. He used one gas tube and it went through the pistol block.

 

Definitely was a unique setup but not sure how well it really worked. It would seem as though it would cause a premature opening which could cause over gassing. Or maybe the small port at the pistol position was just enough to pressurize the gas tube without actually opening the bolt.

[TrickyNicky]

Want to hear something really funky. About a decade ago there was a custom AR builder that would install two functioning gas blocks. He would install one at the pistol position and one at the carbine position. The pistol position would have a very small port and the carbine position would have a normal port. He claimed it helped with recoil as well as reliability. He used one gas tube and it went through the pistol block.
 
Definitely was a unique setup but not sure how well it really worked. It would seem as though it would cause a premature opening which could cause over gassing. Or maybe the small port at the pistol position was just enough to pressurize the gas tube without actually opening the bolt.

I had a similar thought late last year when I was doing my first round of how/why does an ar work research. I had figured that with two adjustable blocks, one could in theory dial in the timing to perfection for any given load. I guess there are no new ideas except old forgotten ones.

It would be interesting to mess with a design like that, for someone like me who is still learning and likes to know as much "useless" information as possible, it would be down right educational. Smarter people could probably figure out in their heads how everything would work together, me I have to actually try stuff and see for myself how things work.