Installing comp/FH . . . does amount of torque affect accuracy?

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10-29-20, 06:15
Leonardo

Quote:

Originally Posted by 556Cliff

Well this might be awesome! :)

+1

Always something to learn from Ned
10-29-20, 08:48
gaijin

Quote:

Originally Posted by Ned Christiansen

I have washers coming from both JP and Armageddon!

I have no familiarity with JP's "double crush washers" Ned, although I have used other products of theirs that were GTG..
Are they advertised as "Precision" washers", for use with tight clearance MD's?
11-11-20, 10:50
Ned Christiansen

Dunno yet. I have the JP's but have not yet had the time to really look them over. I'll wait until the other ones come and then find some time to test / record / report. My rough plan is to check how / what tq it maintains throughout what amount of thread advancement, and how they maintain parallelism as tq is applied, what tq it takes to completely collapse the thing to the point where tq starts increasing to bore-collapsing tq levels-- more or less a destructive test.

I'm kinda expecting both to be exactly the same product, maybe sourced from the same place or one from the other. I mean the crush washers we've been using all these years are, I believe, an off-the-shelf item that has been out there for other industrial applications for years, not a product that was developed especially for the MD application. Seems like I've seen them in industrial catalogs but I never really stopped to investigate.
11-11-20, 14:58
556Cliff

Quote:

Originally Posted by Ned Christiansen

I'm kinda expecting both to be exactly the same product, maybe sourced from the same place or one from the other. I mean the crush washers we've been using all these years are, I believe, an off-the-shelf item that has been out there for other industrial applications for years, not a product that was developed especially for the MD application. Seems like I've seen them in industrial catalogs but I never really stopped to investigate.

The JP Double Crush washers and the Armageddon Tactical crush washers are two completely different designs. Just an FYI before you receive the ones from Armageddon Tactical. ;)

One thing that's supposedly great about the JP double crush washers is that they allow about 1 and a 1/2 turns from initial contact with the muzzle device, while standard crush washers only allow about 1 and a 1/4 turns from contact and the Armageddon Tactical crush washers are actually even less, at only about 1 turn from contact... This is only gleaned from reading the product descriptions though.

The JP double crush washers also stay centered on barrels that have relief cut threads because they are thick enough to where they don't slip into the relief cut like standard crush washers, split washers and shims do. They also stay centered better than the Armageddon Tactical crush washers because they have a slightly tighter inside diameter.
11-19-20, 06:20
Brahmzy

Crush Washers suck.
These: https://precisionarmament.com/produc...washer-system/
Allow for perfect torque, every time, and keep MDs and Suppressor Mounts perfectly timed and straight.
11-19-20, 15:12
Hulkstr8

Quote:

Originally Posted by Brahmzy

Crush Washers suck.
These: https://precisionarmament.com/produc...washer-system/
Allow for perfect torque, every time, and keep MDs and Suppressor Mounts perfectly timed and straight.

I was at an armorer course, building a centy 12.5" + PA washers + FCD 6315KM.

For whatever reason I, nor the instructor, could get the MD and the barrel to time correctly. The instructor took over and got it; although, I worry to this day that there was too much torque applied. It was the only time the PA shim system didn't work out perfectly for me (we also tried PWS shims).

edit: grammar.
11-19-20, 15:22
gaijin

I’ve experienced this.
Have resorted to stoning a thicker PA washer to an “in between” dimension for a proper fit without having to over torque.
11-19-20, 17:51
1168

Quote:

Originally Posted by Hulkstr8

I was at an armorer course, building a centy 12.5" + PA washers + FCD 6315KM.

For whatever reason I, nor the instructor, could get the MD and the barrel to time correctly. The instructor took over and got it; although, I worry to this day that there was too much torque applied. It was the only time the PA shim system didn't work out perfectly for me (we also tried PWS shims).

edit: grammar.

That happened to me the other day with regular shims. Couldn’t get it to time to save my life, without being either a little loose or CRANKED. Very strange. Used a different mount on that barrel instead.
12-12-20, 14:58
Hulkstr8

Quote:

Originally Posted by Ned Christiansen

Dunno yet. I have the JP's but have not yet had the time to really look them over. I'll wait until the other ones come and then find some time to test / record / report. My rough plan is to check how / what tq it maintains throughout what amount of thread advancement, and how they maintain parallelism as tq is applied, what tq it takes to completely collapse the thing to the point where tq starts increasing to bore-collapsing tq levels-- more or less a destructive test.

I'm kinda expecting both to be exactly the same product, maybe sourced from the same place or one from the other. I mean the crush washers we've been using all these years are, I believe, an off-the-shelf item that has been out there for other industrial applications for years, not a product that was developed especially for the MD application. Seems like I've seen them in industrial catalogs but I never really stopped to investigate.

Any update Ned?
12-12-20, 16:33
matemike

Quote:

Originally Posted by gaijin

Well the barrel ID isn't going to "spring back" to original ID dimension. It's steel.

Think about this; the barrel is threaded for muzzle device. The treads are a tight spiral that terminate at the barrel shoulder where washer abuts both barrel and MD.

The barrel muzzle threads are not 90 degree to bore/barrel, but are angled to allow MD to be twisted onto barrel- to contact washer and tighten MD to barrel.
If you keep cranking the MD deeper into barrel you are doing so at an angle to line of bore. It is contacting one side or area of washer first, so washer is stacking pressure on barrel muzzle shoulder un-equally.
A crush washer will be more forgiving in "kinking" or ringing barrel than a Precision/steel washer for the obvious reason the crush washer is designed to compress.
Still, enough torque will eff up a barrel using a crush washer, same as a Precision Washer.

I would use manufacture's recommended torque values or go EASY= enough torque to stabilize/prevent MD from loosening.

I politely disagree about the "angle" at which the MD theoretically contacts the barrel shoulder.
Let's theoretically remove the washer or crush washer for the time being.
Yes the male threads on the end of the barrel are angled in relation to the "straight" linear tube of the barrel. BUT the female threads of the MD are angled in an equal pitch; opposing direction. The ideal intention is for the opposing directions of male/female threads to be so precisely opposite of one another that they bind in a perfectly straight line with the linear tube that they are working on together. ...the bore

If the female threads on the MD were concentric to it's own bore then as it was twisted onto the barrel it would spiral down the angled male threads on the barrel and indeed contact the shoulder at the "off angle" of the male threads pitch on the linear barrel. But since the female threads are not concentric it twists down relatively straight in line.

I have no mathematical engineering proof of this, it is just my own semi-promechanical understanding of threads and their pitch.

Now I do not doubt for a second that MD's and barrel shoulders improperly align all the time. And a crush washer would be more forgiving in those instances. And I also believe that over torqued MD's can possibly ruin the straightness of a otherwise perfect muzzle by pulling on the tip or starting to pinch down on the opening
because it is too tight. But not so much by landing on the muzzle at an angle and torquing unevenly.

To add to the thread. I have removed some factory installed MD's on precision bolt guns that took over 60 ft lbs to start backing off. I have under torqued MD's lots of times. (they start to back off after firing)
I have never over torqued a MD in my minimal experience. At least nothing that made me say my accuracy went to sh!t because I over tightened that MD. My biggest fear when really torquing a MD is stripping the threads or literally twisting off the muzzle. Even though 30 or so ft lbs should never do either of those on a well made barrel, it's my own gut feeling.

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