Effect of twist rate?

[Aguila Blanca]

What is the effect of twist rate?

In context -- a pistol barrel in 9mm or .38 Super typically has a twist of around 1:16, IIRC. I have come into possession of a "9mm/.357/.380" length of barrel blank that I was thinking of using for an off-the-wall project I'm tinkering with. Don't know what the twist rate is, exactly, but looking through the barrel blank and then looking through a 9mm 1911 barrel -- the twist in the blank is visibly faster, and I'd venture to say probably twice as fast.

For handgun bullets in the 95 to 115 grain range, is that twist going to be a major problem?

 

[nicholst55]

Most 9mm factory barrels are rifled 1:10", with 1:16" being the next most common twist. The 1:10" will work just fine for jacketed bullets. Cast bullets, ideally, should be used with a 1:16" twist barrel.

 

[Jim Watson]

You don't have to guess about the twist rate. Push a tight patch through on a swivel handle cleaning rod. Put a mark or a little tape "flag" on it so you can see it revolve as the patch follows the rifling. Mark the rod to start and mark where it has made one turn. Measure the distance between the marks and you have the twist.

As said, many European 9mms have 10" twist (probably 9.84", four turns per metre). That is faster than needed for the usual 115-125 grain bullet, but does not seem to hurt anything.