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Armalite Adjustable Gas Block Help
shooter:
--- Quote from: SS_N_NE on April 09, 2016, 09:42:23 PM ---Drill bits come in a lot of different sizes...more than increments of 1/64".
OK....why do I bring that up? I am a machinist. I use 115 pc. drill sets, since there are fractional, letter and number bits. Don't just grab a fractional bit and drill out your barrel. First, you want to have an exact size and work in small increments. That is going to require a set of number bits or at least the right size individual bit(s). A second thing to consider is dealing with the bur created when a twist drill goes through steel. In other words there is going to be metal sticking out inside your barrel. Measures have to be taken to ensure the bit can not get across the bore and damage the other side of the barrel. Nicks and burs in a rifle bore can lead to a lot of strange shooting problems. Bur removal and bore inspection are not cheap DIY items inside a gun barrel.
Stripped threads can be drilled up a size and threaded for an oversize setscrew...or thread repaired with a heli-coil or similar thread repair system. The thread repair kits are not especially cheap and should be done in a drill press or milling machine to ensure centered and square drill/threading for the repair threads.
--- End quote ---
add in metric bits to, plus all the ones that are just sold by the .001,
Silver:
My eyes suck, they used to be fantastic :angry: anywho, the set screw *seems* to thread in fine but when it is fully in, you can feel it tighten then suddenly get loose and begin to retighten. I am unable to see anything wrong with the screw but I haven't taken a magnifier to it yet either.
I'm gathering my thoughts as what to do next.
Parts wise, I'm sitting on the original gas tube inside a non-adjustable gas block. I also have the new, stripped adjustable gas block.
What I should probably do before I take any non-reversible action (widening the gas port) is to make 100% certain I'm aligning the gas port and gas tube perfectly. If I can determine that and the rifle still isn't operating correctly, then I can feel better about drilling into the barrel.
I really appreciate the cautionary notes about "just drilling the hole wider" because I definitely wouldn't have considered everything you mentioned. "more than increments of 1/64" That was comforting to hear also. I was doing some math and trying to figure out how 64ths would get the necessary increments needed and I was concluding they wouldn't.
SS_N_NE:
--- Quote from: Silver on April 09, 2016, 10:35:44 PM ---My eyes suck, they used to be fantastic :angry: anywho, the set screw *seems* to thread in fine but when it is fully in, you can feel it tighten then suddenly get loose and begin to retighten. I am unable to see anything wrong with the screw but I haven't taken a magnifier to it yet either.
--- End quote ---
Yeah...my eyes have never been good. Glasses, bifocals and old age don't help much. Optivisors are my friend. I would definitely pull the block and take a look at things to be sure what the issue may be especially since you could be making a problem that you do not have yet. Almost sounds like the set screws are short and passing completely thru the threads...which seems odd. If the screws are passing thru the threads, maybe a trip to the hardware store for some longer setscrews could fix the problem. Is the block the correct size for the barrel...tight slip on fit? Not loose (rattle around loose)? a wrong block could be indicated by short setscrews.
I would measure the distance of the barrel port to the block stop on the barrel and then measure the block port to ensure the ports line up. It is good practice to dimple the barrel by drilling shallow marks into the barrel to better maintain the setscrews. As you know from removing the original block...the mounting systems are very different.
And, a good point by Shooter (guess I didn't want to be too confusing) drill bits come in any size needed. MSC, Enco...etc are machine supplies that have all size of hole making bits.
Don't be afraid to seek out a gunsmith...sometimes their experience is cheap compared to the results of inexperience.
Silver:
Yeah, the block is the right size. It's not a clamp on. It is not tight but it is snug (I can slide it on without marring the barrel but it does take a tiny bit of pressure).
Thanks for the rest of the advice. I'm going into "slow down, be patient" mode because everything up til now has been reversible. I'm going to be very deliberate before I take any non-reversible actions.
Thanks for your guys' advice.
Silver:
Fixed. Even though I am lacking appropriate measurement tools, I was able to determine the gas block needed to come forward about a 32nd or 64th of an inch (guesstimate). My AR is back to semiautomatic and kicking like a mule. Feeds and ejects perfectly. Glad no drilling was not needed. Lots of lessons learned. Thanks for the advice and suggestions.
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