Polygonal rifled barrels

[tightgroup tiger]

Do polygonal rifled barrels yield more velocity than a traditional rifled barrel?

I don't have a normal rifled 9mm anymore of the same barrel length as my Walthers to compare.

My PDP may just have a fast barrel but the velocities I seem to get with it are usually higher than I normally think they should be.

I was just wondering if anyone else has tested this?

TT

 

[CoalCrackerAl]

Here is a good read on them. Under design it explains about the velocity.

Polygonal rifling - Wikipedia

en.wikipedia.org

Design​

Hexagonal polygonal rifling.
A number of advantages are claimed by the supporters of polygonal rifling. These include:

• Not compromising the barrel's thickness in the area of each groove as with traditional rifling, and also less sensitive to stress concentration-induced barrel failure.
• Providing a better gas seal around the projectile as polygonal bores tend to have shallower, smoother edges with a slightly smaller bore area, which translates into more efficient seal of the combustion gases trapped behind the bullet,[4] slightly greater (consistency in) muzzle velocities and slightly increased accuracy.[1]
• Less bullet deformation, resulting in less frictional resistance when the bullet travels through the barrel, which helps to increase muzzle velocity. The lack of sharp surface deformation on the bullet (rifling marks) also reduces drag in flight.

 

[Jim Watson]

I suspect that the lack of corners on the hammer forge mandrel improves tool life, too.

There are few target guns with "polygonal" rifling. Not zero, but most are "land and groove." That may have more to do with the cost of the hammer forge than the rifling plan. Cut rifling is a lot easier to make to order.

 

[tightgroup tiger]

Thank you, I'm at work now, I'll read that in depth when I get home. But you cut out answered my question.
TT

 

[James Petti]

I have a single example of poly G barrel, a Glock 30. It is one of 6 handguns that either are .45 ACP or have a conversion cylinder for that cartridge. I sometimes load shotshells for them and the best patterns (tighter-longer range) are from that short M30. I suspect that the shot cup, a .410 does not get much if any spin imparted to it by the poly shape, than it would from the more grabby lands of a traditional barrel. As for velocity, my chronograph skyscreens mean more to me than knowing how fast they might go in which gun. Not sure that the shotshells are of any value, anyway.

The history bit is useful, thanks.

 

[GeoDudeFlorida]

Back in the 80’s I loaded FMJ in 9mm almost exclusively. I had an H&K P7, Star M30, Walther P38, and Star BM. The P7 and BM are close in barrel length. What I noticed was that the difference in velocity was within the SD but the P7 was much more accurate. The BM could shoot swaged lead more accurately and the P7 was just not compatible with lead. A gunsmith I was friends with in Merritt Island said the P7’s gas-rebatement system was probably more nearly responsible for the accuracy and better numbers than the polygonal rifling.

The M30 and P7 were brand new designs back then so not much was really known about either.

 

[Charlie98]

A number of advantages are claimed by the supporters of polygonal rifling. These include:

It's funny... all 3 of those points could be made about Marlin's MicroGroove rifling, but it gets lambasted constantly.

I had a Kahr P45, with the poly-g barrel. I deleted my notes on that pistol specifically (I don't have it any longer...) but if memory serves it's 3.5" barrel was a little faster, believe it or not, than my Kimber's 4" barrels.... the velocities were nearly the same, even considering the missing 1/2" of barrel.

 

[tightgroup tiger]

A gunsmith I was friends with in Merritt Island said the P7’s gas-rebatement system was probably more nearly responsible for the accuracy and better numbers than the polygonal rifling.

I hadn't thought about that, but that could help add to the velocity also, the fact that H&K and Walther both use the stepped chamber for a better gas seal. I thought my Garmin C1 was reading fast when I first got it, until I shot my GP100 over it. I was then reminded how much pressure the b/c gap vents off.

 

[tightgroup tiger]

Design​

Hexagonal polygonal rifling.
A number of advantages are claimed by the supporters of polygonal rifling. These include:

That's just about what they look like,
MyQ5 Steel frame pro match barrel.
The PDP SD Pro looks just like it.

 

[Varminterror]

I’ve built and rebuilt AR uppers with around 50 polygonal rifled barrels - yes, they’re faster, yes, they’re easier to clean.

I think the gas seal and bullet deformation “advantages” are grossly overstated.

Accuracy for poly cut barrels, like all barrels, is dependent upon the quality of the barrel, not just upon the type of rifling. Among barrels of their price and quality, in general, I can’t find any difference in performance on target - If poly cut barrels were destined to be more accurate, we’d never build rifles with other rifling types.

 

[EricBu]

I'm indifferent, I've got a few things with them, since they all shoot better than I do, I can't really say they are any better side by side. My favorite thing about them is all the CZ82s I've picked up with "shot out barrels", hahahaha.

 

[tightgroup tiger]

I have no idea accuracy wise, if there is a difference between the two types of riflings. I'll never know. I just didn't know if I had a fast barrel or if they poly barrels were faster in general. It was making me wonder about my Garmin.
Now I know.
Thanks guys.

 

[LiveLife]

Do polygonal rifled barrels yield more velocity than a traditional rifled barrel?

That was one of several marketing claims Glock made due to smooth rounded rifling for better gas seal and less friction discussed in this thread - https://www.thehighroad.org/index.p...glock-handgun-see-below.847392/#post-11047664

This is KKM barrel with conventional square cut "land/groove" rifling

This is Glock six "Hexagonal" barrel with smooth rounded rifling. Left showing from chamber end and right showing from muzzle end (BTW, 45ACP Glock barrels have five "Pentagonal" rifling)

Gen 5 Glock 17s now have GMB (Glock Marksman Barrel) with additional ridges along each hexagonal rifling - https://www.ssusa.org/articles/2017/9/1/preview-glock-gen5-pistols/

Here are close up pictures - https://www.glocktalk.com/threads/gen-5-barrel-rifling.1686073/