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Old 03-20-2017, 07:20 PM
jinx18
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Figuring out twist rate on unknown barrel



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Hi I have a barrel I am trying to figure out twist rate on. It could be 1-16" or 1-9". I don't have a cleaning rod with a swivel head to use. I only have a patch worm and I don't think that is accurate enough. Is there any other way to tell? Just eyeballing down the bore looks the same as a 1-16" but I never looked down a 1-9" to know if it appears much different as well. Thanks.

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Old 03-20-2017, 08:03 PM
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You don't need a swivel head. Patch a jag on your rod and place it in the chamber. Mark it with a line all the way lengthwise, then a line crosswise at the start. Push it through, count the number of times your lengthwise line crosses a fixed point on the barrel, and when the jag pops out the muzzle, make another crosswise line. If it's a 1:16, and an 18.5" barrel, you'll see your lengthwise line once and it'll end up just past where it started. If it's a 1:9 18.5", you'll see the line exactly twice. 99.9% of 22LR barrels are 1:16. GM I believe makes a 1:9, and I think it'd be marked as such. They also make a 1:18, and that's probably about it, although anything is possible.
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Old 03-21-2017, 07:09 AM
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Or make that lengthwise line, mark the rod at the barrel, mark it again when it has turned 360 degrees, and measure between marks. 16 inches = 16:1, etc.

In the rare case of a short barrel and a long twist, find the length of rod for half a turn and double it.

Last edited by CardPuncher; 03-21-2017 at 10:36 AM.
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Old 03-21-2017, 10:01 AM
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While maybe not as precise as actually measuring the twist, as the other posters have suggested, eyeballing should get you pretty close...

If you follow a single groove of rifling for 1", how many degrees around does the location shift?

1/16 rotation is 22.5 degrees
1/9 rotation is 40 degrees

If determining degrees is difficult for you, then maybe translate it to "hours" as seen on an old analog style clock face:

1/16 rotation is 3/4 an "hour" (3/4 x 1/12)
1/9 rotation is 1+1/3 "hours" (4/3 x 1/12)

Hope this helps!
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Old 03-21-2017, 10:39 AM
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3 of us have gone to a fair amount of trouble to give the guy an answer he can't use because he doesn't have a rod. Just a patchworm. Well, Jinx, you'll know just what to do if you ever decide you need a rod.
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