The gas tube and block are from "expo arms"
The gas tube and block are from "expo arms"
Many gas block/barrel align short of the step to allow for the front hand guard cap. I generally take a straight edge and draw a line with a pencil or sharpie down the center of the gas port on the barrel so it will be visible both for and aft after you put on the gas block. I then measure (usually with calipers but if you don't have any you can eyeball it) the back of the gas block to the middle of the port hole inside (usually around a 1/4 of an inch). Next you can put a line with a sharpy in the middle of the port hole on the back of the gas block (which is center of where you gas tube enters the gas block). Now measure to see if the gas block align short of the step to allow for the front hand guard cap and add for that space if needed. Align your line on the block to that on the barrel and you should be good to go.
This is what I am talking about with the lines but he is not factoring in the hand guard retainer gap if needed
I'll have to give it a try once I'm home. I appreciate the advice and will update you guys once I figure it out.
There's also the dimple jig used to add an indexing dimple across from the gas port.
This dimple then aligns the gas block during installation and helps retain the set screw.
Black River Tactical
BRT OPTIMUM Hammer Forged Chrome Lined Barrels - 11.5", 12.5", 14.5", 16"
BRT EZTUNE Preset Gas Tubes - PISTOL, CAR, MID, RIFLE
BRT Bolt Carrier Groups M4A1, M16 CHROME
BRT Covert Comps 5.56, 6X, 7.62
I'm not familiar with Expo Arms, so am not sure if it's worth retaining.
Both BRD Engineering and SLR make jigs that are easy to use, and it doesn't take long to do it if you've got the tools/skill.
Last edited by grizzman; 10-29-19 at 19:48.
Once you have lines, etc drawn and the block / tube installed, I normally do the following:
1. Tighten the block a little snug but where you can slide it a little. Firmly plug the barrel extension within the receiver.
2. While holding a finger over the end of the tube in the rcvr, blow through the barrel. There should be no air escaping.
3. If it holds, remove finger and blow. Check for good flow.
4. If curious, very slightly move the block to and fro and note difference in flow.
5. Find the sweet spot and tighten the block down very well. Double check.
Some manufacturers will instruct the block should be positioned X-distance from the journal (approx a thin business card). All of mine are butted up to it and work great. The port in the block is normally significantly larger than the port in the barrel thus allowing a decent "slop" factor. But you still want to strive for the best position.
The tube should be perfectly centered through the opening of the rcvr with no bind or touching. As long as it easily moves easily in and out of the gas key of the carrier, you should be good.
Once you are sure the gas block is properly installed, check the gas tube for drag in the carrier.
This should be a standard part of any gas tube replacement.
Gentlemen I have an issue I got a 7 inch tube to replace what looked to be another tube that was a hair too short it appears I've come up short again I replaced the random block with an Odin arms one also. I'm not sure what my issue is pics will be incoming shortly
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