lilja barrels and gas blocks

[cst]

Since they have a flat spot milled in the barrel for the set screws...how are you guys finding the retention of the set screws vs on a dimple? I was thinking about pinning a block but done know if they removed too much material to do it?

[mongoosesnipe]

If your starting from scratch I would use a clamp on block so as to not introduce and stress into the barrel from a set screw or pin

[cst]

Ive heard all the theories on accuracy...I asked Dan from Lilja and he feels that set screws do not effect accuracy...I am split on which way to go.

[mongoosesnipe]

As long as the barrel is stress free and the screws are not over tightened they should not effect accuracy but I figure why risk it I use clamp on blocks on all my builds they are usually about the same price and only slightly more bulky if at all

[cst]

I hear what ur saying..do u feel that clamping may be more retentive than setscrew? I am trying to build a rock solid tactical rig..thats why I was gonna pin it

[Klem]

I hear what ur saying..do u feel that clamping may be more retentive than setscrew? I am trying to build a rock solid tactical rig..thats why I was gonna pin it

Yes.

Clamping is the latest innovation in gas block retention. Originally it was pinning and then set-screw. There seems to be general agreement that set-screws are not as solid as pinning and have a tendency to come loose, especially if the gun is worked hard. This is unacceptable for those who trust their lives to the gun.

There does not seem to be the same doubt about clamping. When you think about it set-screw designs 'pull' the top of the block down to create the bind. When tensioned, the only parts of the block making friction contact with the barrel is the inside top and the tips of the screws at the bottom. This is less efficient than a block designed to flex as it is clamped. Clamping has more surface area contact with the barrel for a better seal and more friction. This probably has a bearing on keeping the clamping screws from coming loose. But, they still use screws to clamp and any screw can come loose.

There are some low profile clamping designs out there. Daniel Defense and VLTOR are two low profile designs of clamping blocks.

[mongoosesnipe]

I have never had a gas block come loose either set screw or clamp on, I think as long as your building a DI gun you will be fine either way but I think the clamp ones hold a little better and apply holding pressure more evenly

[montana]

I have never had a gas block come loose either set screw or clamp on, I think as long as your building a DI gun you will be fine either way but I think the clamp ones hold a little better and apply holding pressure more evenly

Ditto

[cst]

All the GAP 10s and Larue ObRs are all set screw...im not sure how deep a dimple they put on em....but if it was an issue im sure we would have heard it.

I figure if my motorcycle can handle clamping tripples on the forks then itnshould be damn tough for a rifle...?

[Drifter]

FWIW, the gas block seat on my Lilja barrel measured ~0.755", so I used a Rainier Arms Low Profile Match Grade 0.755" gas block. Still had to tap it on.

https://www.rainierarms.com/?page=shop/d...ct_id=1872

[cst]

Im going to get the new Sentry adjustable gas block from SLR.... just going back and forth between pin and clamp

[explorecaves]

Im going to get the new Sentry adjustable gas block from SLR.... just going back and forth between pin and clamp

Which one is this?

[Drifter]

Im going to get the new Sentry adjustable gas block from SLR.... just going back and forth between pin and clamp

I suggest clamp-on in case your barrel is 0.755" like mine, as the clamp-on would likely better accommodate it. This, of course, assumes that the clamp-on style will fit under your handguard (if applicable).

[cst]

Which one is this?

http://www.ar15.com/forums/t_3_124/63834...Block.html

[LRRPF52]

I have never had a gas block come loose either set screw or clamp on, I think as long as your building a DI gun you will be fine either way but I think the clamp ones hold a little better and apply holding pressure more evenly

I've seen gas blocks come loose. They were all set screw types. It will happen with guns that are run very hard on a high volume schedule, or are run in extreme cold on a high volume schedule.

The worst thing you can do is use an aluminum gas block with carbine-length gas systems. Even MLGS beautifully-machined 7075 T6 aluminum failed on a Mid Length Gas System AR15 that I tested in extreme cold for this very purpose.

On a Rifle Length Gas System, you can get away with aluminum because the port pressure is much lower, but I personally will never use Aluminum on the gas blocks.

If I use a set-screw attach, I prefer to also bed the gas block with Red Loc-tite, after a detailed and thorough gas system trouble-shoot, preferably with actual shooting.

[cst]

I've seen gas blocks come loose. They were all set screw types. It will happen with guns that are run very hard on a high volume schedule, or are run in extreme cold on a high volume schedule.

The worst thing you can do is use an aluminum gas block with carbine-length gas systems. Even MLGS beautifully-machined 7075 T6 aluminum failed on a Mid Length Gas System AR15 that I tested in extreme cold for this very purpose.

On a Rifle Length Gas System, you can get away with aluminum because the port pressure is much lower, but I personally will never use Aluminum on the gas blocks.

If I use a set-screw attach, I prefer to also bed the gas block with Red Loc-tite, after a detailed and thorough gas system trouble-shoot, preferably with actual shooting.

So what are you using in your builds? Clamping or pin? Do you think you can get away with clamping on a duty gun?

[LRRPF52]

I use them all. For a precision gun, a set screw gas block that is bedded and has some method of securing at least one of the set screws into the barrel underneath is fine, especially when the gas block is underneath the handguard.

On my 16" Grendel with AA barrel, I currently have a clamp-on JP gas block that I machined down, made lightening cuts to on the sides, re-profiled the front of the block at an angle, blasted, and Cerakoted. I've never had that gun choke unless I tried a Magpul PMAG as a test to see if 3 rounds would feed.

For an exposed, standard Front Sight Base, you of course will want it pinned, as there is leveraging opportunity for the FSB to torque and come loose if it was set screwed, but I doubt many people will be installing standard FSB's on these Lilja barrels.

I think clamp-ons are probably the best method for getting a uniform seal around the gas block journal, and I haven't seen one come loose. You might also consider Loc-tite compound on the machine screws that clamp the gas block around the journal, and use an inch pound torque driver to balance the compression of the gas block around the barrel.

When installing a gas block, we tend to make assumptions that all the parts on the market should fit, however, a good AR15 smith or hobbyist will measure their gas block journal, as well as the ID of their intended gas block. Many need reaming, but reaming too much can bite you in the bung. I have also temp-fit gas blocks and barrels, where the journal was slightly too large. Place the barrel in the freezer, and heat up the block with a hot air gun (not open flame). Then quickly fit and trouble-shoot the parts. That makes for a very secure set screw gas block to barrel install.