Thread: How do you determine barrel twist rate?

Hi guys,

I got a Valmet Hunter M88 in .308... unfortunately not with the original barrel!
So far I've had one guy briefly look at it and give a best guess that it's a 1:10 twist rate and probably a Tikka barrel (SS as well).

Is there a sure-method to test this? Should I just take it to a smithy? My knowledge is quite limited.

Cheers.

if you have a cleaning rod its easy.
push a patched jag or brush into the barrel and start to draw back out.
Mark, a point, on the cleaning rod, (flush with the end of the barrel), slowly pull rod back, and when the mark is back at the same point, (360) deg, measure the distance between the barrel end and the mark, this will give you a measure per revelation, ie twist. measure in inch, as twist is generally in imperial.
so if you get ten inch its 1-10, 14 inch 1-14 etc.
best to do it a few times.

@vorno

Let Larry Potterfield show you how it's done.



Cheers
Pete

Thanks guys, perfect analogy.

...Kinda wish I knew all this before I bought 100 rounds of 148gn .308 winchester ammo! My Valmet really does not seem to like it!

Define like eg sideways holes in the target, big random groups what? 308 is normally 1:10 and 148 gr should be in the sweet spot as thats the original bullet weight the roind was developed on. What is the twist rate anyhow, there is a formula for working out max bullet size for a particular twist but there are lots of other possible causes.

thought most 308s were more like 1:12 especially on a shorter barrel

Originally Posted by dedubyah

thought most 308s were more like 1:12 especially on a shorter barrel

Two most common 308 twist rates are 1:10 and 1:12.

Although 1:11 and 1:13 twist are not unheard of especially in match rifles.

However I believe the Winchester 308 standard is 1:12.

Cheers
Pete