Polygonal rifling

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walkin' man

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Does anyone know the effect of polygonal rifling on ballistics tests? On guns like the USP are you able to tell which particular pistol a bullet was fired from? Has anyone ever seen one under a microscope? Does it flatten the sides of the bullet? Anyone know how many sides there are to the inside of a HK USP barrel? Is this enough questions for one post? Is this my last question for now? Yes.

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land of the free and the home of the brave......WHETHER THEY LIKE IT OR NOT
 
I believe that the HK USP has a Hexagonal profile for the rifiling. The advantage of polygonal rifiling is that it supposedly distorts a bullet less allowing better accuracy and higher velocity. I don't know if this is true, but it sure sounds nice. Also it is supposed to be easier to clean. As to telling which weapon a projectile was fired through, yes you can tell the difference. Even though the modern manufacturing processes used to make the barrel are veery consistant, a noticable difference sneaks through. Also, no two bores are cleaned te same way, so differences are made that way too.
 
FWIW, my USP45c appears to be hexagonal. I can say that it is at least as accurate accurate out of the box as my SIG 226 (or at least I shoot it as well, hard to say, but it is impressive, none the less). Tha downside to polygonal barrels is that they don't like lead bullets, as it tends to clog teh rifling. I have read where Glock recommends against using lead bullets, but I'll have to re-read my H&K owner's manual to be sure on the USP (I don't recall it saying anything about avoiding lead bullets, but they say as you age, the memory is the second thing to go and I ferget the first ;o))
M2
 
An advantage is reputedly higher velocity with this type of rifling. The downside is your gun may blow up when you use lead bullets. Not a good trade IMHO. What was wrong with regular rifling that it needed to be fixed?
 
A qualified firearms examiner and AFTE member can do ballistics matches with the "smooth" bores. Yes it is a bit harder. NYPD had some special rifeling barrels made up for them but dumped the idea. The poly barrels typically give better velocity with less "blow-by"

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Vinny
 
AC,

I have not heard of any guns blowing up with lead bullets, but polygonal rifling does not grip lead bullets as conventional rifling does, and the bullets tend to skid rather badly, leading the bore and losing accuracy.

I don't know why makers went to that type of rifling but I suspect it may be to reduce blow by when a bullet does not completely fill the groove and also probably because it is cheaper to make than conventional rifling.

As a rule, auto pistol makers, especially in Europe, don't care about reloaders or the use of lead bullets and those issues do not concern them or influence design.

Jim
 
My P7M8 is hexagonal. Yes, ballistics tests can match bullet to firarm. Here's something I heard at a Smith and Wesson sale at a local gun shop. Don't laugh because this might just be a bunch of bull. One of the sales persons told me he heard there is an issue with the S&W acid etched, laser rifled, .22 auto pistols. Rumor goes it is almost impossible to match bullets fired with the pistol used. Could just be a fairy tale.
 
Glock .45 ACPs are octagonal. A hex pattern that large with enough flat to grip and stabilize the slug would be too "undersize" in diameter between the flats/lands.

The crime lab guy I talked with said there was NO PROBLEM identifying polygon barrel-marked bullets. The only challenge is the same as with conventional rifling--if the bullet is damaged too much on impact, the identifying characteristics can be scrubbed away.
 
1st generation HK-USP 9mm does have conventional land and groove type barrel. They change it to polygonal looking rifle-ing around 1995 as all their barrel are now hammer forged. The land/groove is in a round radial form instead of square notch cut land /groove shoulder thus the polygonal looking. About HK goes KB and polygonal looking barrel inaccuracy. First, HK do not recommend reloaded ammo. and second, HK test fired it with a bullet blocking in the barrel. It still shot as if nothing in there. Third, an out of the box HK-USP Match helped me won a few 50 meters bulleye matches along with other Les Baer and a Para P14 Signature model. Unlike my G17, it tolerates limp wrist very well. Lately, it is one the pistol I shoot least as it becomes too accurately boring and no I do not work for HK. Sierra Lima
 
Jim Keenan, You haven't heard of the exploding Glocks? I don't know all the particulars as Glocks don't interest me but there have been multiple blow ups and it is with lead bullets and high pressure rounds, especially the .40.
 
First: Don't use lead in a polygonally rifled barrel. They do not tolerate the build up of lead like traditional barrels. There are no spaces to be filled in with lead. The smear of lead causes a reduction in the diameter of the bore.. that is bad..


Second, I own an HK 45, a Jericho 941, a Desert Eagle .44 and several Glocks that are all polygonallly rifled.

Polygonal rifling not only offers an increase in velocity, but the barrels are much less prone to wear than lands and grooves.. there are no edges or lands to wear out, so the barrels should basically last forever. Glock has two 9mm barrels htat have over 1 million documented rounds through them and they are still within factory spec.

Lastly, to answer yourmain question, it is sadi that you cannot tell the difference between any two particular pistols through traditional ballistics test when they have poilygonal rifling.
In other words, you might be able to tell a Glock 45 from a USP 45 (both Hexagonal), but you couldn't tell two Glock 45s from one another.


[This message has been edited by Rob (edited May 07, 1999).]
 
Great topic with differing opinions! I can only speak from my own personal experience from shooting my H&K P9S .45 Target for the past 20+ yrs. The gun has had approx. 35,000 rounds through it and it is the most accurate pistol I have owned. I have four custom built .45's from well known Guild members and none of them can match the accuracy of my "out of the box" stock P9S.
The only other pistol that closely matches it's accuracy is my SIG-P210.My H&K has a polygonal bore and I routinely (weekly) shoot Bull X 200 gr. SWC lead through it.I always end my shooting session by shooting 2 mags full of hardball. MY gun shoots lead better than than any jacketed load! I have shot and won many bullseye competitons with this gun and can't seem to do as well with my Colt's.
I have never heard of guns blowing up until I read some forum responses and I mainly shoot lead bullets.Please note that I have always cleaned my gun after each shooting
session by the Ultrasonic method.(see my response to "fal308" in Gears and Access thread). Bottom line: I feel that the H&K P9S
was the greatest .45 out of the box ever manufactured; it is the "greatest sleeper".
Any H&K P9S fans besides me out there?
 
DDS, yes, I'm also own one of those polymer framed, stamped metal slide with a funny looking shark fin front sight and SA trigger stopper lever. If I have to have only one, it will be the one. have a good day, Sierra Lima.
 
SierraLima:
Good to know that there are others who appreciate the brillant design of the P9S. With its delayed roller lock action (breech-block), exquisite adj. trigger , and ergonomic grip allowing a low bore axis alignment with the hand , it doesn't get any better. Unfortunately, due to its high price when introduced and lack of an "Americanized" mag release button it didn't sell well except for military/law enforcement. If you shoot yours alot make sure you change your buffer occasionally. Enjoy your fine pistol!
 
AC and others,

Yes, I have heard about Glocks blowing up. I have seen a report of a burst barrel in firing reloads, but that was a 9mm and FMJ bullets, not lead.

I would be interested in hearing from someone who had a blowup, but only those to whom it actually happened, not reports of happenings to someone else, somewhere, some time.

Jim
 
DDS,

You are a very lucky person.

To shoot FMJ (which doesn't "give") through a leaded polygonal bore is kinda like smoking a cigarette in a fireworks factory.. you can only do it for so long before an ash lands on something bad.

Shooting FMJ does not "clean out" a barrel that is significantly leaded. Instead, the leading could retard the movment of the projectile and cause it to ladge int he barrel. While this may not cause the barrel to rupture in and of itself, a quick follow up shot could be horribly disastrous.

While you may feel comfortable doing this (hey, sometimes I ride my mortorcycle without a helmet, so I understand....), I hope no one tries it out.

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-Essayons
 
ROB:
I was not inferring nor did I state that shooting hardball through my gun was an attempt to "clean out the bore". I shoot the hardball and other jacketed hollowpoints that I use as my carry loads to reaclimate myself to the recoil and functioning. My lead loads are reloaded for target purposes. Obviously you have not taken advantage of the excellent results attained by using ultrasonic cleaning.I DO NOT have an unsafe pistol with a leaded barrel.Why does one assume that because you use lead bullets primarily,that leading is a result even if well maintained?
As to riding a motorcycle w/out a helmet , please don't do that. I have been a rider for over 30 years and in year 22 I was hit head on by a car entering my lane. I was very lucky to survive and fortunately was wearing a full face helmet which was destroyed , but saved my face.

[This message has been edited by DDS (edited May 07, 1999).]
 
Glocks have had problems because they have a partially unsupported chamber, not because of their method of rifling. And this mostly in the high pressure .40 S&W. I've shot mostly lead exclusively in my Glock 21 and have never had any problem with it. I also had a .45 HK P9S and shot vast amounts of lead through it with no trouble. Of course, these guns were usually kept very clean (as all guns should be...). Polygon barrels seemed to lead a lot less than convention rifling. They are also far easier to clean. My USP has the older conventionally rifled barrel and it leads badly and is a real pain to clean.
 
A while ago on Glock Talk a guy posted ballistics between his Glock factory barrel and a KKM barrel (conventionally rifled) for 40 S&W. The KKM barrel had consitently higher velocities (about 35 fps) than the Glock barrel for all loads. So much for the velocity theory. Perhaps KKM is just a realy good conventional barrel, and other conventionally rifled barrels suck in comparison. I don't know.

I'm of the opinion that most Glocks that blow up are due to over charges, or over charges in combination with the semi-unsupported chamber. I have read of a few cases where some dork fired 2,000 high velocity lead rounds through a barrel without cleaning it and it finally blew up. Golly Sarge!

Yes, Glocks DO lead up faster than conventionally rifled barrels. I have both and I've compared them (albeit qualitatively). However, you can shoot lead safely through them if you clean the bores thoroughly and often and don't load them to extreme velocities. If you break these rules then you're on your own.

Steve Koski
skoski@geneva.com
 
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