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Posted: 8/10/2004 11:45:24 AM EDT
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I've traced down a hot rifle short stroke problem to a Vulcan Arms aluminum 4 rail gas block that I've put on a Bushmaster H Bar barrel. When I removed the gas block I confirmed the problem by wiping off the carbon & crap on the machined band of the barrel. I've thought of shooting until the hot / short stroking occurs and then tightening down the gas block again but I'm worried this might strip or break the screws. I've also noticed the Vulcan clamps on by having a slot cut through the bottom rail and two horizontal screws to pull the gap together. Most (all, I think) of the others in the Brownells catilogue have set screws against the barrel. Should I try the reset while hot idea or is it a poor design, try to exchange it for another, maybe another brand? Suggestions? Due to the gas tube design they all leak around the tube and roll pin so I'm thinking no help there  Thanks Edited to add link to pic: Vulcan Arms Gas Block @ Brownells |
If that's true then that's probably the problem|
Since you already own it, then I guess we may as well get it working. First thing is to make sure that there is at least a slight gap between the bottom slot when tightened. If not, then it's time to go to work with a jewelers file and open up the slot. You should have at least a 1/16" when the bolts are tightened down between the two surfaces. Now since the block can be slit to remove it, this brings up a few options on making a gasket to seal and prevent the leakage between the ports. Since I have good luck with using Blue loctite on keys to carriers to make a thin gasket (hand lapping short cut), my solution would be to lay a thin coat down around the gas port on the barrel, then tighten down the block. If you need to remove the block at a later date, again you can either pry open the slot to break the bond, or just use a heat gun. Once you have the block in place, use a rubber tube and blow down the gas tube to remove any loctite from blocking the port passage (blow it into the barrel). Don’t worry about a thin layer on the sides of the ports, the gas pressure/heat will clean this fine layer out during the first few shots. Note: Before you loctite the block, make sure that you make a few pencil marks on the block, barrel to align the ports before the loctite sets up. |
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