Really weird question, odd-thread bolt (nuts and, not gun)

[Diamondback]

Anybody out there in Gunsmithing/Hardware Land have any ideas that might help me find a bolt threaded at 1/2-28 like an AR barrel, or a line on somewhere I can find a threaded end from a junk barrel for cheap?

Really, I only need a threaded section and maybe an inch to inch and a half after that--I'm trying to work out some timing-washer stuff to see how much more I need to grind off my blast-deflector mount and I can't fit it to my live barrel until I do a Bobbit on the bayonet lug, so I'm thinking to use another bolt or barrel as a "test stand" to figure out how the BFD mount affects timing on my muzzle brake.

Read More

 

[Lilhigbee]

28 TPI is .0357" per thread, so shortening the blast deflector .0357" will allow it one complete rotation. Take whatever fraction of a turn you need to get the correct index and multiply .0357" by that fraction. Example; if you need another 1/4 turn to index your blast deflector, .0357"X.25= .009". Shorten your blast deflector .009" and it will rotate another 1/4 turn. Ain't math grand??

 

[Diamondback]

Thanks, @Lilhigbee -- may not be applied precisely how you were thinking, but those numbers were very helpful. I should note that I have the Precision Armament Accu-washer timing set--bare brake with no washer runs out of thread not fully seated at a skosh off 10:30, and no-deflector uses a #8 (each # = 20, so 160deg or 0.0159"--the area I'm grinding down isn't the flange itself but the tapered "tail" that goes around the barrel behind it. Based on your numbers, the mount flange on my ICD BFD is equivalent to a #47 washer, when the ideal would have been a #44 (two #18's plus my #8); next "sweet spot" to correctly index my brake would be at #62, which would put a #15 washer behind the flange both assisting with timing and acting as a de-facto barrel extension to reduce the back-end grind.

0.5" from FSB-front to threads +~.03" #15 washer + ~.09" front flange for mount = WCS overall grind-down to about 5/8". On paper at least, the end of the grind is in-sight...

 

[erslll]

Anybody out there in Gunsmithing/Hardware Land have any ideas that might help me find a bolt threaded at 1/2-28 like an AR barrel, or a line on somewhere I can find a threaded end from a junk barrel for cheap?

Really, I only need a threaded section and maybe an inch to inch and a half after that--I'm trying to work out some timing-washer stuff to see how much more I need to grind off my blast-deflector mount and I can't fit it to my live barrel until I do a Bobbit on the bayonet lug, so I'm thinking to use another bolt or barrel as a "test stand" to figure out how the BFD mount affects timing on my muzzle brake.

Do you live with an ATF agent?

 

[Diamondback]

Do you live with an ATF agent?

No, it's a matter of the other stuff physically WILL NOT FIT because the bayo lug projects forward into the area where the deflector needs to go, and I don't trust myself with a hacksaw.

 

[erslll]

Ok. Fair enough.

 

[Diamondback]

Let's put it this way... with my klutz gene, if I had a nickel for every time I've barely managed to avoid losing a finger I'd be able to afford keeping a gunsmith on retainer to do this stuff for me on-demand.

 

[Lilhigbee]

@Diamondback would you mind posting some pictures of what you are doing?? I think I understand the problem, but would be curious to see the pieces involved.

 

[Diamondback]

Best pic I have, this is with the brake but no collar... the washer is a Precision Armament #8 (160-degree timing) Accu-Washer.


The mount for an Indian Creek BFD is the thing on the right in this photo (shown with thread protector; left is joined collar/mount and center is collar only):

It's 3/4" from the front face (wide, top end) back to the point of the rear taper. Gary at ICD and I between us figured out that I need to grind 1/8" off that to bring it down to a 5/8" OAL, the front flange is about .093" and the rest of that 5/8" is timing washer and the available end of 10.3" barrel. (I'm about 1/32" from target.)

Basically, the plan is to shave the collar down until with it and the timing washer bottomed out against the barrel shoulder, the rear flange JUST clears the FSB--and every fraction of an inch I get that front flange closer to the shoulder is the same amount of overall length reduction, a big deal on something meant to go into a laptop case.

 

[MasterChief]

I'm sorry if this is a dumb question but can you not remove the BL and replace the pin?

 

[Diamondback]

Those FSB pins are in there solid enough *I* can't drive 'em out to separate FSB from barrel--this thing came to me fresh from the factory. The bayo lug is an integral casting with the rest of the FSB.

Maybe a pro smith with a better range of hammers and punches can, but with my duffel-bag toolkit... and as noted, it'd be a *real* bad idea for me to take a hacksaw to that lug myself rather than outsource the job--the increased budget is well worth the avoided blood-loss and medical bills.

 

[MasterChief]

haha....I understand crapper-gunsmith! I'll be working on better ideas.

 

[Diamondback]

haha....I understand crapper-gunsmith! I'll be working on better ideas.

Actually, I think I've got it... *if* I've figured the math right, the mount is equivalent of two #18 washers plus a #11... deducting the two #18s since those are full 360-degree turns, threading a #11 onto the barrel as a "stand-in" trial-and-error resulted in needing to use a #3 washer to get to the same index position as a bare-barrel #8.

DOH! I'm SUCH an idiot... I could just build a test-stand from a couple pieces of craft-store dowel rod, one at 3/4", other at just over half, drill a bore big enough to take the small dowel in end of the big one and use the brake's own threading to cut the threads.

And there's a craft store right across the parking lot from where I end up dragged for chow once a week... I feel like a total frickin' moron not thinking of this before I posted.

 

[MasterChief]

Glad I could help