Determine Barrel Twist

[41magsnub]

I have a post-64 Winchester Model 70 22-250 with a bull barrel on it. A buddy of mine asked me what the barrel twist rate is on it. Where would one even start to determine such a thing?

As a side note, would it even matter what the twist rate is?

Thanks!

 

[gcrookston]

use your cleaning rod and brush/patch. you can measure out the length and mark. Insert the rod until it is well seated in the rifling. Mark. Push through until it makes one complete revolution. mark. remove rod, measure the distance...

 

[Vern Humphrey]

Yes, it makes a difference. A faster twist is needed to shoot long, heavy bullets accurately. This is quite a common factor in .22 varmit rifles -- in the .223, a 1 in 12 twist might be standard, but to shoot the heaviest bullets requires a twist as fast as 1 in 7.

Your .22-250 was probably built to shoot 55-grain bullets and if so would have a relatively slow twist. If you wanted to shoot heavier bullets (say 65 grains or heavier) you might find it will not shoot them accurately.

 

[41magsnub]

thanks, disregard the question. Search finally decided to work for me, came up with crap for results the first time. This is an OLD question!

 

[mc223]

You will need a cleaning rod. A patch. A small piece of tape. And a Tape measure.
Remove the bolt.
Attach the patch to the jag.
Make a tape flag near the handle of the cleaning rod.
Insert the cleaning rod - patch assembly into the breech a couple inches.
Note the position of the tape flag.
Hold the tape measure next to the cleaning rod with 0 inches at the flag.
Push the cleaning rod into the barrel till the tape flag makes one revolution.
The number of inches on the tape measure represent the twist.

Yes it does matter as some bullets will not perform well from a slow twist. Longer heavier bullets need faster twist to properly stabilize.

If I had to guess. Your barrel is between a 1 in 11 and 1 in 14. Shorter lighter bullets would perform best with the slower twist.

 

[41magsnub]

The slower twist would seem to follow, the gun loves the smallest rounds I can find for it, gets squirrelly with larger stuff.

 

[Vern Humphrey]

The slower twist would seem to follow, the gun loves the smallest rounds I can find for it, gets squirrelly with larger stuff.

That seems about right. One of the problems with fast twist is they stress the bullet. At high velocities, the stressed bullet can literally come apart in the air as it leaves the muzzle. With really high velocity cartridges like the .22-250 that's a serious possibility.

 

[Jim Watson]

Nearly all .22 centerfires had 14" twists until the Army started messing with the .223. That is adequate for a 55 grain flatbase spitzer, but of course any individual rifle might do better with something lighter.