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Posted: 11/23/2008 7:50:59 AM EDT
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(AR15performance/constructor fanboys please do not reply, this is a technical question)
I had a custom barrel put on my upper and it has been a real turd. in another thread I posted photos of the workmanship, but I got that all straightened up. Upon test firing the rifle short strokes. IF you look at the photos below it appears that the gas block is drilled a bit too close to the shoulder, and the gas block cannot get over the gas port in the barrel. it is also off left/right. My expectation is that I can use a dremel tool on the dimple on the bottom to fix the left right part. But what about the front back? Dremel the gas block opening to be bigger? Any other thoughts? 
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Quoted:
If you paid for a 'custom' barrel you should not have to do any mods to it. Whoever did the bbl f'ed up I would make them fix it... It was a mess when I got it. The BBL guy told me the main problem was with the handguard. So I had the handguard repaired by the handguard mfg. Then the bbl maker told me that the warranty was now void because someone else had worked on it. But based on how poor the work was I don't know that he has the skill to repair it. I am hoping to fix it myself as I am going to be hunting with it about every weekend between now and the end of January. I a ma good enough shot that it does not need to load itself, so worst case I can get through the seasons without a final solution. |
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Looks like you're still having some workmanship issues to me.
I'd leave your Dremel in its case. If you've got a set of calipers, the dimension from the gas block shoulder on the barrel to the center of the gas port should be .310" (ish). If you purchased the gas block from your builder and/or supplied it yourself, and the builder knew you weren't going to run a typical handguard, that dimension could be shorter. If your gas block was tight up against the shoulder, you've got two fairly easy options. Remove some material from either the gas block face, or the barrel shoulder face. I'd probably lay the gas block on a surface grinder to shorten it up, the barrel shoulder is a job for the lathe. In looking at the picture, it looks as if it doesn't need to come back more than .020" or so. Sending you a PM. |
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^^ +1. If you open up the hole in the barrel you're going to over gas it and have no end of trouble. N/M I see where it is now. Just ream out your GB a bit. I think you may be having other issues though. In the top pic it looks as if the holes line up OK. Not centered, but not obstructing one another.
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If this is the same rifle I saw pics for one of the posters noted that the gasblock was too far back and might have been blocking off part of the port. It's off the other direction. can't get the gas block far enough back. I talked to bfarrin1 on the phone. he is going to help me get it squared away. (Super nice guy!) I'll be hunting single shot this year though. |
| Get to a belt grinder and shave the required amount off the rear of the gas block check for function and if needed you "may" have to slightly shorten the gas tube You want a straight shot into the gas block, not a bunch of curves. Sorry you had to have this crap, another alternative is have the .750 shoulder extended slightly to the rear by a real gunsmith |
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Quoted:
If you look at the first pic it looks like the gas block hole is just covering the gas port. I put it on and off a few times with a shot or two fired in between. In the ring you see, the inner circle represents the actual gas block hole. Subtle adjustments affect how bad the short stroke is. I have not gotten a single round to load. Best case is a clean ejection. |
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Looking at the pic, moving the gas block anywere but against the shoulder will cause problems. I would follow bfarrin1's advice & take a little off the back of the block. From what I see it may need to have the gas port opened up. What cal is this upper? Sorry if I mised it.
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Quoted:
Looking at the pic, moving the gas block anywere but against the shoulder will cause problems. I would follow bfarrin1's advice & take a little off the back of the block. From what I see it may need to have the gas port opened up. What cal is this upper? Sorry if I mised it. cal is .308 the gas hole is 3/32 |
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I would get a new gas block that doesn't use the same holes as what you currently have insted of trying to dremmel out the dimple.
I would also shave the end of the gas block vs messing with the shoulder, and checking the tube length in the upper after all is said and done. I would also call the BBB or someone and get heat on the crappy barrel maker-that is a piss poor job. |
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Quoted:
I would get a new gas block that doesn't use the same holes as what you currently have insted of trying to dremmel out the dimple. I would also shave the end of the gas block vs messing with the shoulder, and checking the tube length in the upper after all is said and done. I would also call the BBB or someone and get heat on the crappy barrel maker-that is a piss poor job. You got that right!!! The best way to get the required amount off would be a belt sander with a jig to keep the shoudler square if you know anyone with a mill, have them flatten the bottom of the barrel about 1/25th of an inch where the dimples are that way your not stuck with just one gas block |
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