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Posted: 7/17/2004 2:54:05 PM EDT
| Thinking ahead to Sept. I am going to put either an A2 or Vortex on the dissy, any info on threading and installing or who to send it to to have the work done? |
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ktak56, we're in the same boat. I have a Bushy with the plain (no MB) 16 inch barrel. From my research to this point, the end of the barrel must be a certain minimum diameter before threading (something like .469). My barrel is way over this minimum, so I assume that I am stuck with having someone turn down the barrel and then thread. If your barrel is already threaded and simply has a muzzle break pinned and welded, there are other options. I hope that others on the board may be able to share more info, or options, on the matter. |
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Anytime you make external or internal threads you have to turn or grind it to the right diameter. Like if you turn 1/4-20 threads you need a .250 OD. TO make internal threads you take 1 divided 20(for 20 pitch) and come with .050. Now subtract that from .250 and that is the hole size you need to tap a 1/4-20 thread. I think AR's use 1/2-28 but Im not positive so youd need to make sure the bar/barrel was a .5 OD. The best way to do it is with a lathe and chase the threads but dies would work too. I bought a tap for flashhiders from Brownells and Im sure they sell the die too. On the two barrels on my AR which are both threaded are stepped down before the threads. I dont know how big of an OD a pencil barrel would have but that would be the closest thing I can think of to come close to .500. I cut and threaded my M17 barrel and was surprised how soft and easy it turned. I was using tin coated cutting inserts though and not a high speed cutter like alot of the hobby lathes use. |
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Yes, the NATO standard muzzle device thread is 1/2-28 TPI. A tap and die sizingchart will confirm the major diameter which is nominally half an inch, of course. Barrels are usually made of SAE 4140 or 4150 alloy steel. It's tough and very wear resistant but isn't really all that HARD. Use carbide tooling to cut it and if the chips don't come off blue, you're not hitting it hard enough. Your surface finish gets better if the cutter has a lot to do, assuming it's in decent shape. Take up to .050 per pass with carbide tooling in the lathe and you'll get a mirror finish off a good cutter and rigid lathe. CJ |
| One other thing to keep in mind its that your point of impact will probably be different after you have your barrel threaded and have a FS installed. Problems can happen in any step. Depending on the skill of the gunsmith it could turn out great or not so good. After I had my BM 16 in threaded it shot way to the right. It turns out that the barrel was torqued to much to the L. It took 14 clicks to zero. Prior to that it was dead on. I reinstalled the barrel myself and now it zeros at 1 click to the R. Overall I am satisfied as it cost me $75 for the cutting and threading and included a phantom FS. However, you really never know what will happen after having this done. If you have great shooting post ban barrel you might want to leave it alone. |
How is that? I know you can overtorque the barrel but dont see how it could be cocked one way or the other unless the upper mating surface bent or deformed or it had some gunk between the upper and barrel when it was installed. Dont try .050 cut unless your on a RIGID ASSED lathe! 
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