Barrel Rifling

[Izzy360]

As most all of you know, beside the PM9 I own a M&P9c. I took them both apart for my weekly fluff and buff. Sorry I'm a nut. I started to compare things between the two. I noticed the barrel rifling is very different. There's nowhere near as much rifling to the M&P9c as opposed to the PM9. Can anyone tell me why that is. From my research the M&P9c is supposed to be extremely reliable and accurate. I have no complain as I probably wouldn't notice the diffrence all I know is the bullets hit where I point it. So does that mean the PM9 is as accurate if not more accurate? The slides look exactly the same so does that mean that the PM9 is as reliable as the M&P9c? Tue frames are pretty close, subtle differences but basically the same. what's up with that? Can someone help me out? I'm confused? On another note I hear they are trying to comPletly re-write the gun laws in Mass. I also hear that even a violent convicted felon can get a fid card 5yrs after conviction? What's up with that? I think they will get all their gun right back at some point. Can some of you weigh in on this as I just found all this out today

[kpm9]

Barrel rifling should be differnet, two completely different types of rifling are used. Polygonal and Std Land/Grooves rifling.

[Bawanna]

I thought the M&P was polygonal rifled also but I dont have one here to look at so I could be way wrong on this one.

[kpm9]

That's H&K, not M&P. Well.. Glock has polygonal rifling also ;)

[jocko]

M & P no polygonal.. My M & P after David Bowie at Bowie tactical got done with it would shoot um in the same fokking hole. It was a disgusting gun!!!!! I sold it, as it was just to accurate for such a clux like me owning it. Bowie certainbly did a number on my M & p. Took to long to get all his work done though, but he is good , VERY GOOED. Polygonal rifling could not have made one bit of different either..

[HadEmAll]

Just an observation about polygonal rifling versus land and groove in the Kahrs.

My previous K40 had polygonal rifling in the "match grade" barrel. Popular legend has it that polygonal rifling will provide a higher velocity for the same barrel length over conventional rifling due to lower friction.

I was very interested in comparing the 2 types when I acquired my CW40 with its "non-match", conventionally rifled barrel.

Velocities from the CW40 were 9-22 fps higher using the same loads versus the K40. Of course the CW40 barrel was also a tenth of an inch longer than the K40 barrel.

And I could never prove that one outshot the other at the range.

So in the Kahrs, I don't see any difference in either velocity or accuracy from the P series polygonal or the CW series conventional rifling. Certainly not enough to make that the basis for choosing one over the other.

[CJB]

All sorts of claims are made for polygonal rifling... you really cant make a valid comparison on two barrels, but you can draw a picture with broad brushstrokes.

The question in my mind... is how do they put polygonal rifling in that big hunk of steel that kahr machines away? Usually, polygonal rifling is hammer forged, and that appears to not be the case with Kahr's Lothar Walther barrels. I suppose they could button rifle them, or maybe the blanks are hammer forged and we just done realize it.

[jocko]

kar's lothar barrels are button rifled. Have no idea how the standard non polygonal kahrs barrels are made.

[kpm9]

When talking velocities there are to many variable to compare a STD rifled barrel to a poly rifled barrel. barrel length is one, but variances in tolerances could easily explain why the CW40 barrel is experiencing higher velocities. Assuming the same ammo, same powder, same temperature of barrel, same ammo temperature...you get the point.

[jocko]

20+ feel plus or minus in any barrel make up would not matter to me one bit. I don'[t see any person saying the polygonal rifled is more or less accurate than a standard rifled barrle, expecially in a kahr. U ain't gonna shoot one holers anyhow with a kahr, Barrel might do it but the shooter ain't gonna do it, so this stuff is nice to chat about but put no precedence into any of it. If the gun is reliabe, then just shoot it like you stole it..

[O'Dell]

I've had polygonal [H&K's and Kahr's] and conventional [S&W, SIG, etc] and I never noticed much difference. The H&K's are accurate, but so are the S&W's, especially the M&P's, and SIG's. Maybe the polygonal barrel is a bit easier to clean, but that's it.

[CJB]

kar's lothar barrels are button rifled. Have no idea how the standard non polygonal kahrs barrels are made.

Thanks for the input Jocko.

The conventional barrels are most likely button rifled too.... Mostly because we have three ways to rifle barrels - hammer forge, button, or cut (broached). We have effectively ruled out hammer forging, since you can make a rifle barrel out of a blank the size LW supplies Kahr. That is to say, hammer forged rifle barrels start life short and squat, and get the living snot pounded out of them, with "hammers", to make them long and thin, and profiled, and rifled, all on one operation. Cut rifling involves pulling a series of gang broaches through the barrel. This is a relatively slow and exacting process, also requires precision drilling, and also leaves a rather rough surface finish that must be cleaned up. So... that leaves button rifling, where a carbide (or other magic metal) "button" is hydraulically driven through the rough drilled barrel. I say rough drilled, because the drilling is not as precise as it needs to be for cut rifling - where the "lands" are the surface, and surface finish, left by the drill.

[jocko]

glad u know what the hell ur talking about, u lost me after the thanks for...............