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Posted: 11/5/2013 2:50:28 PM EDT
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I am about to send my 14.5" barrel off to get a muzzle brake permanently attached. I know I have to put the barrel nut and gad block on the barrel before since it would not be possible to do after. I got the barrel nut on with no issue of course, but I'm having issues with the gas block. This is also my first build, wanted to put that out there.
The gas block is the YHM-9383 but it is not sliding onto my barrel once it gets to the next part of the profile where the gas port is. Can anyone give me some insight, should a lot of pressure be used to get it on? should it be well oiled? could the gas block be out of spec? 
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| Some are tight. No offense but it is the right diameter (hard to tell in the pic, but it looks right) and the set screws are backed out enough right. I have had GBs that I had to tap on with a hammer and some just slide right on. Most of my tight ones were on coated barrels though. |
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Quoted:
Some are tight. No offense but it is the right diameter (hard to tell in the pic, but it looks right) and the set screws are backed out enough right. Yes set screws are backed out, barrel calls for a .750 gas block and that's the YHM model, don't think they make a .625 one like that, trying to find my calipers now to do a quick measurement. |
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Maybe lube it little and take the set screws out so you can tap on it without vibrating the set screws out and losing them. Also after you lube it kind of twist it as you go.
ETA: also check for any high spots or burrs on the block and barrel that may need to be dressed with a file or sanding block. |
Tried using some oil to lube it up and push it on my hand, then did some tapping with a rubber mallet, still couldn't get it on all the way. Once I took it back off I noticed that the inside of the gas block had developed a lip, it was not there before. I'm not sure if the barrel or the gas block may be out of spec since I don't have others to compare, using a set of calipers both measure to .750, am I doing something wrong?
 
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I've assembled many of those gas blocks using a variety of barrels (brands) without issue.... With the permanently attached FS, I'd seriously consider a 2-piece design... you never know. But to answer your question... while I've had some tight ones, never have I had to pound/beat one on. Most definitely appears to be a case of tolerance stacking perhaps...
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| If you do not have a heat gun you can stick the barrel in the freezer and the gas block in the oven for a bit and then try it. I have also used a brake cylinder hone (ten bucks or so at auto parts store) in a drill with some oil to knock off any rough areas inside the gas block. |
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If mine I would buff down the inside of the gas block with some 200 grit wet/dry to smooth things up. Then I'd heat the crap out of it with a heat gun, move into position and call it a day. NO NO NO NO! Heat the gas block to slightly expand the metal, it should be snug, this has usually worked for me. You do not want to start removing material that can not be replaced. Rainier arms makes a gas block that is 5 thousandths bigger for match barrels as an alternative |
| Notice I said to use the 200 grit wet/dry to SMOOTH THINGS UP. You must comprehend what you read. He has already swaged a lip on the inside edge of the gas block. That lip of metal is likely to scratch his barrel at the least and inhibit a good tight seal at the worst. He has to smooth out that deformed part of the interior of the gas block. Then install it by heating or freezing. It is a whole lot easier to heat a gas block than it is to freeze a barrel. |
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