Twist question

[Waddy]

My M&P 10, serial number KN 121xx appears to have a 1-14 twist, rather than the 1-10 in most .30 caliber rifles, and what it says in the S&W catalog. I have measured it several times using a cleaning rod, bore brush and piece of tape marking the starting point and measuring the distance when it makes one complete turn. Several of my other rifles and calibers measured "as advertised". Was the M&P 10 ever issued with a 1-14 twist???

 

[Jessie]

Is it .308? I haven’t heard of any of those that weren’t 1/10.

 

[Waddy]

Yes, definitely .308. It makes no sense whatsoever. Especially the difference from 1-10 all the way to 1-14. It must be something in my measuring technique, but darned if I can come up with a reason.

 

[pantannojack]

Chubby Checker might know.

 

[Goblin]

I’d try a bore jag with a tight patch and see if you get the same results. The brush may be skipping over some of the grooves instead of precisely tracking the twist.

 

[Jim Watson]

Right, use a tight patch.
A 14 twist is something you would see on a score benchrest rifle shooting nothing longer than 130 gr flat base.

 

[Waddy]

Headed to the shop to try a jag and patch. I will let you know, thanks.

 

[Waddy]

That worked, 1-10 twist, just like it is supposed to be. My only guess is that my brush was TOO tight, and would not let my cleaning rod handle rotate freely enough. Thanks for your help everyone.

 

[luvsmiths]

That worked, 1-10 twist, just like it is supposed to be. My only guess is that my brush was TOO tight, and would not let my cleaning rod handle rotate freely enough. Thanks for your help everyone.

[ame]https://www.youtube.com/watch?v=MerCZJHIejs[/ame]