Velocity difference between Polygonal vs Rifled barrels?

[mudfish]

I've read claims that polygonal barrels yeild a slight velocity edge over rifled barrels. In a compact pistol with a 3" barrel, a few extra fps could really help.

Has anyone chrono'd the two side by side with the same ammo? Say a PM series vs a CM series of the same caliber?

[paul34]

For what it's worth, I don't think a few extra FPS would help one way or the other, IMHO.

[Tmygun]

I've heard it can go both ways; with some poly rifling giving higher velocity and some convential rifling giving an edge. Some break even. I agree that any difference is very marginal and not of any advantage in the real world.

Tmygun

[Tmygun]

BTW: I'd like to see Kahr come out with a P380 with conventional rifled barrels at $200.00 less:D.

Tmygun

[mudfish]

So has anyone tested it? Like 5 or 10-shot averages from each barrel?

[HadEmAll]

I chronographed several loads in the past with my previous K40 and current CW40 before I sold the K40.

The CW40 with conventional rifling had higher velocity with all loads over the K40's polygonal rifling.

UNFORTUNATELY... the CW40 barrel is also .1" longer. So in this case, the miniscule extra length appears to trump any velocity advantage of polygonal rifling.

These are all 6 round averages:

Winchester Ranger 155 grain JHP - K40=1168 fps --------- CW40=1175 fps
Remington Express 155 grain JHP - K40=1127 fps --------- CW40=1149 fps
Federal Classic 155 grain JHP - K40=1108 fps ------------- CW40 1117 fps

The largest impact on muzzle energy was only around 18 pounds with the Remington

[HadEmAll]

I also have a Beretta 9mm/Glock 9mm with comparable barrel lengths. The Glock with polygonal rifling, and the Beretta with conventional rifling and chrome-lined.

The Glock does generate around 12-20 fps more with each 9mm load I've chronographed. However (there's always a however) this could be just chamber dimensions or bore diameter as much as rifling style.

And the operational characteristics of the pistols are so different that that would make me choose one over the other more than a little velocity difference. Again, the difference in muzzle energy is inconsequential.

[les strat]

In a 3" barrel, I would say difference is trivial at best.

[HighSpeedBail]

This was posted by the guy at Gunblast.com


http://www.gunblast.com/Kahr-45s.htm


GunBlast.jpg (http://kahrtalk.com/attachment.php?attachmentid=3912&stc=1&d=1307657352) See attached picture...........



As can be seen in the chart above, velocities were also very close. I had expected that the polygonal rifling of the P45 would give slightly higher velocities, but the converse was true in this case, with the CW45 posting slightly higher velocities with almost every load tested.