Polygonal rifling - any experience with it


Well-Known Member
I had no idea the twist was that tight! What were they thinking? Seems like that may increase
pressures, too.

I think the basic issue is that Glock just blew the dimensions on their chambers on the first couple
of gens of 40s. It was a very new caliber, and very different than all others, not terribly surprising.



Redlands, Kalifornistan
The Glock chamber theory you post is a very likely explanation.

The 9mm has had a fast twist rate since Day 1. Maybe the early smokeless propellants used in Europe required the twist to propagate combustion, or 4 turns/meter twist was all that European barrel makers wanted to make (think Mauser milsurp rifles here). Mauser made a lot of the P-08 and variants we call "Luger" pistols over the years. I dunno. I just treat 9mm, 40 S&W and 10mm like a rifle caliber when it comes to cast bullet loading--high pressures, fast twists, strict adherence to dimensional integrity, relatively hard alloys, relatively soft lubes.