Velocity difference

[Kevin Kline]

Hey,

Did some chrono'ing today. I chrono'ed the same load out of my 35 with the Glock factory barrel and the Barsto barrel. The Glock barrel has the polygonal rifling and the Barsto has standard lands and grooves. The Barsto was for a Glock 24 and was cut shorter to fit the 35.

Suprised by the difference in velocity. The Glock factory barrel was consistently 22-25 fps faster than the Barsto. I'd always heard about the polygonal rifling increased pressure and velocity, and figured it did somewhat, but didn't realize it made that much of a difference.

Also, I chrono'd the same load out of the 35 with the Glock factory barrel and my Sig 226ST. What a shock. The Glock barrel was 60-70 fps faster than the Sig. I know the Glock barrel is 5.3 inches and the Sig is only 4.4 or 4.5 inches, but wow, that is quite a difference. It takes at least .3 of a grain of powder, and sometimes .4 extra for the Sig to catch the same velocity as the Glock barrel.

[Flexmoney]

I had similar results with my G35...and a cut down KKM barrel for a G24.

I had to bump my powder up a tenth or so.

[Duane Thomas]

It's not that the polygonal rifling increases pressure, but that it gives a better gas seal around the bullet, and less friction as the bullet travels down the bore, thus higher velocities.