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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