Yet another firearm rumor?

[kellyj00]

I've heard you can't shoot cast lead bullets from a polygonally rifled firearm such as a Glock or a H&K pistol.

After reading the wiki on polygonal rifling, and doing a bit of research on google and the H&K moderated forum, I'm even more confused. Some say that lead builds up faster on polygonal rifling, causing unsafe pressures. I've read a post from a Glock user saying that he's fired many 1000's of lead through his g21 with no issue, cleans it every 500 rounds or less however.

I see how polygonal rifling works, and it looks to me like it would has less to go wrong.... it looks much simpler on the wiki. It seems like a traditionally rifled barrel would have more issues as there's 1) more surface area 2) deeper grooves to be leaded.

Can anyone tell me of any experiences with polygonal rifling and lead? I'm amazed that glocks and H&K's which have great torture test results could be turned into unsafe, malfunction-prone pistols by something as simple as lack of a copper jacket.

Thanks!

 

[dmrodco]

Well I have an HK USP and the barrel looks like traditional rifling to me I am no expert though. I have shot 155 gr hard cast through it and it shoots just fine matte of fact its pretty accurate too !

 

[jfh]

and I blew up a Glock 20 using cast bullets,

and I don't think it was an overloaded cartridge. I've posted about it a few years ago--search it up if you wish.

Although I was only minorly injured, it did sour me on Glocks. This was an early model, just after they came out. I've heard others say they have no problem--so go with what makes you comfortable.

Jim H.

 

[dmrodco]

I think the glock problem , from what I have read and seen has more to do with the unsupported case than anything else. My HK is fully supported and I have no fear of a case rupture escaping the chamber

 

[fatelk]

This is a controversy that has been hashed over many times, with strong opinions on each side.

Personally I have shot many cast lead bullets through my .40 cal. Glock 22. Many will tell you that this is a no-no that is sure to make your gun blow up, but I had been doing it long before I'd heard that. I use relatively light loads, good quality bullets, good brass, watch the barrel for leading, and have had absolutely no problems.

I too would like to hear from someone who knows more about polygonal rifling than I regarding the leading issue. This is a very persistant rumor, there must be some truth in it to at least some degree.

 

[kellyj00]

I've read that Glock says something in their manuals about not shooting lead. And the wiki on Polygonal rifling suggests that this is due to other factors other than polygonal rifling.

Is there any scientific reason why cast bullets cause issues with polygonal rifling? I'm not a scientist, or even that smart of a fella, so after reading up on polygonal rifling, I'm thinking that polygonal rifling is not only a good idea, but simpler than the traditional grooved rifling, and could cause LESS issue than the grooved type.

My understanding is that with polygonal rifling, the bullet follows the land areas, whereas with traditional rifling, the bullet is marred by the grooves and expands or fills them so it takes on the rifling characteristic as it leaves the barrel. So, how could lead...or anything else....be more of an issue with what seems like a simpler design?

 

[RustyFN]

According to the Armorer at the Glock match it is safe to shoot lead in a stock Glock barrel if you use the correct size bullets. He told me ( for example ) if you are shooting a 9mm Glock then you would want to use a hard cast lead bullet that measures .358. He said the leading was caused by the hot gas going past the bullet. He also said most problems happen when people shoot lead and then load a mag of FMJ and shoot them without cleaning the barrel first. The lead will collect in front of the FMJ and make a donut, then at some point swell the barrel enough to let the FMJ through. It will still be shootable but there will be a ring of lead in the barrel that you will never be able to get rid of and the accuracy will start to go down hill. Just to be clear he recomended to not use lead or plated bullets in a polygonal barrel.
Rusty

 

[Vern Humphrey]

I think the glock problem , from what I have read and seen has more to do with the unsupported case than anything else.

It's the combination of leading and an unsupported case. I've seen a photo of fired cases lined up -- a tiny bulge begins to show just forward of the web, and shot after shot gets bigger and on the final case, the case wall blows out. This was ascribed to the lead fouling preventing the round from chambering fully, resulting in more fouling farther back towards the breech, until the gun fired without the case seated.

Is there any scientific reason why cast bullets cause issues with polygonal rifling?

if you are shooting a 9mm Glock then you would want to use a hard cast lead bullet that measures .358. He said the leading was caused by the hot gas going past the bullet.

Note that .358 is the upper limit for .38/.357s, and too big normally for 9mms.

See if you can recover some fired Glock bullets -- you will often see the recovered bullet has flats with curved sections connecting the flats. This tells you the bullet didn't completely fill the bore -- if it had, there would be corners where the curves are. This is where the gas blow-by occurrs.

 

[Sheldon J]

Hummm... I've put over 2K SWC's through my USP .45 with no problems.

 

[Bad Flynch]

>This is a controversy that has been hashed over many times, with strong opinions on each side.<

Yep. Some say it is the firing of reloaded and weakened cases in the chamber (again) with a large unsupported area. Some say it is the polygonal rifling. Yes, the largest bullet that will chamber should be used to avoid gas cutting. However, here is something else to add to the pile of possibles:

Gage-block seizure. Evidently Glock barrels are super slick on the inside, slick enuff to cause the lead to adhere on a molecular level, much as gage blocks stick to a surface plate. At least one leading reloading authority (not me) has proclaimed that publicly and he has actual industry experience. Moreover, I know him to be really technically astute and as honest as he can possibly be.

 

[kellyj00]

forget it, it'll just get a new barrel.

 

[Jim Watson]

Before you buy a new barrel, compare the prices of cast and cheap plated bullets. Then figure out how long it will take the new barrel to pay for itself.

 

[SCW]

FWIW, before I knew how to check the internet for everything, I had a Sig 229 in .40 S&W that used polygonal rifling. I noticed that it leaded up really bat to the point where after a hundred or so shots I'd have curls of lead peeling out of the rifling.

I took the barrel out and used a bronze brush covered with cloth and coated with JB Bore Paste, and polished that barrel for several hours over the course of a week or so. From then on it shot lead just fine. YMMV.

 

[FLORIDA KEVIN]

You might want to try some of those polymer coated bullets from Precision Casting ?

 

[Master Blaster]

If you are going to fire lead in a Glock you can do it safely, using good hardcast bullets (penn Bullet co Hint Hint) and proper sizing of the bullets, 1/1000 smaller than for conventional rifling like for 9mm .355 instead of .356 IIRC.
Even then you have to keep a close eye on the leading and clean the gun thoroughly.
I have done it in the past in my G34 and G26.

BUT

In 9mm I like berrys plated or ranier ballistics plated hollowpoints, they shoot very well out of my two glocks, and they don't foul the barrel.

Polygonal rifling is designed for harder jacketed bullets not for shooting lead. It has a greater area of bore contact with the bullet which raises pressure and raises velocity. If you use the wrong lead bullets with improper sizing and drive them too hard it can cause dangerous fouling in a polygonal barrel.

Glock doesnt say dont shoot lead in either of my manuals, I have read this on the error net and looked very carefully for those words, they AINT in the Manual provided with either pistol.

They do say DO NOT SHOOT RELOADS, many other manufacturers also say this because some people do not safely reload, and glock doenst want the liability, hence the caution and disclaimer.

 

[Archie]

From page 15 of "Glock perfection Instructions for use, for All Glock Models, form US005(REV 8/99)" (printed in English, French and Spanish).

Paragraph 26.

Only use high quality commercially manufactured ammunition, in excellent condition and in the caliber of your pistol.

[I'm skipping the list of what caliber for which model pistol.]

The use of reloaded ammunition will void the Glock warranty, due to the unpredictability of the standards (SAMI/NATO) adhered to, since reloads of poor quality ammunition may not meet (SAMI/NATO) specifications, may exceed limits, and therefore be unsafe.

This is the standard, "You're probably an idiot who will blow yourself up and we're not going to be part of it" warning.

Does anyone see anything about 'lead bullets'?

Does anyone have another manual, issued by Glock with a later revision date, which has information or warning significantly different from this citation?

I'm not interested about what someone said on another forum, or what someone's step-uncle who has a friend who knows a guy who used to work at Glock said. Anyone have anything documented as coming from Glock that stipulates lead bullets are not to be used?

And just for the record, Glocks do not have polygonal rifling. Anyone here take geometry in High School? (And remember it?) From Plane Geometry (Revised) by Palmer, Taylor and Farnum, 1915;

A polygon is a close plane figure formed by straight lines. The lines which form the polygon are the sides of the polygon. The perimeter of a polygon is the sum of its sides... A polygon which has all its sides equal is an equilateral polygon… A polygon which has all its angles equal is an equiangular polygon. A regular polygon is both equilateral and equiangular.

I trust everyone agrees the cross-section of the bore of a firearm is most likely to be a regular polygon? That is, the top section is not going to be longer than the bottom or sides? Looking at the barrel of the Glock in my keeping, the cross section of the barrel is most definitely not a polygon. The sides are not straight and the lands are most assuredly arcs. It looks to me – as I look down the muzzle of my very unloaded Glock 17 – like conventional rifling, except with the edges of the lands worn off.

On the other hand, looking at the rifling of my H&K USP40, the cross section looks exactly like a drawing from the geometry text, next to 'regular polygon'.

Yes, I know, Glock says they use polygonal rifling. They must have a different definition of polygonal. Just like China (PRC) says Tibet and Taiwan are really part of China and always have been. Just like Hamas says it wants peace. Just like President Clinton "…never had sex with that woman…"


Leading
When the .357 Magnum was introduced in 1935, one of the big problems it had was leading. Running a 158 grain SWC lead bullet – even a hard one - down a barrel at 1500 fps ends up rubbing lead off the bullet and leaving it on the barrel. Some people reported loss of accuracy due to leading in as few as 18 rounds. No one ever reported blowing up a .357 Magnum due to excess leading. Just for the record, the pressure levels for both 9x19 and .357 Magnum are 35,000, according to Ammo & Ballistics 3 by Bob Forker.

I once personally shot some several hundred rounds of factory wadcutter through a Ruger Security Six. So much, that when I cleaned the revolver, lead came out of the barrel in strips. I honestly didn't think lead would build up like that. Not only did the gun not blow up, but shooting didn't give me any indication of the lead buildup.

In closing…
I've reloaded ammo for some thirty-seven years now. I've loaded for pistols, revolvers, rifles, carbines, shotguns and muzzle loaders. I've loaded hot loads and soft loads and much in the middle. I've shot reloads in products of Colt, S&W, Ruger, Charter Arms, Remington, Winchester, Marlin, Heckler and Koch and several military surplus thingies. Some had bores that would not shoot lead bullets accurately, but none were ever bothered in function by lead bullets.

Frankly, any gun that will not handle properly loaded ammunition with lead bullets is either poorly engineered or really badly made.

I've had this Glock for several years now. It shoots adequately and is suitably reliable. But 'perfection'? If it's perfect, why won't it handle lead bullets?

 

[tbtrout]

The early USP's were made with traditional rifling. I do not know when they switched.

 

[Master Blaster]

polygon

closed plane figure bounded by straight line segments as sides. A polygon is convex if any two points inside the polygon can be connected by a line segment that does not intersect any side. If a side is intersected, the polygon is called concave. In a regular polygon the sides are of equal length and meet at equal angles; all other polygons are not regular, although either their sides or their angles may be equal, as in the cases of the rhombus and the rectangle. The simplest regular polygons are the equilateral triangle, the square, the regular pentagon (of 5 sides), and the regular hexagon (of 6 sides).


Glocks do in fact have polygonal rifling.

http://www.glock.com/english/index_pistols.htm

They call it hexagonal or octagonal but it is still a polygon equal sides and all.

Frankly, any gun that will not handle properly loaded ammunition with lead bullets is either poorly engineered or really badly made.

I agree, i had a Beretta 92 Inox made in about 2000 it would keyhole after 15 shots of my hardcast lead reloads, the bullets hit the target sideways and left a perfect profile, nose up, down, sideways, at 50 feet. The barrel would be filled with shreads of lead hanging from the rifling. It shot jacketed bullets just fine.

I sold it a while back.

 

[Steve C]

've heard you can't shoot cast lead bullets from a polygonally rifled firearm such as a Glock or a H&K pistol.

There's a lot of difference between "can't" and "not a good choice". You can shoot all the reloads using lead you want in a Glock but its just not a good idea. In my experience with the Glock 19 9mm, lead bullets just don't produce the accuracy out of it that you get with jacketed bullets. Yes, a few rounds of lead and the bore is pretty well leaded. If you like to scrape out lead and think the 2 cents a round you save is worth the 30 extra minutes of cleaning then more power to you.

In the Glock 40's and 45's the issue using reloads isn't lead bullets but unsupported chambers causing KB's from weakened cases that rupture. There are plenty of shooters out there that continue to shoot reloads in their Glock 40's and 45's with factory barrels and have yet to have a KB but it is a risk despite those who say that its "safe" because they've shot X number of rounds without a problem.

 

[Jim Watson]

Sorry, Master B., I agree with Archie. My geometry teacher said a polygon was a figure made up of straight lines and there aren't any inside a Glock barrel. If you want to see a polygon barrel, look at an 1860s Whitworth hexagonal bore.

I think that there is a lot of stuff said about "polygon" bores that may be true - easily cleaned, slightly higher velocity, less tolerance for lead bullets, etc. - but is not relevant to Glock policy. I think they use it because it gives longer tool life in a hammer forge barrel machine; no sharp corners on the bore mandrel to wear off.

 

[Master Blaster]

http://www.firearmsid.com/A_bulletIDrifling.htm

Hammer Forged Rifling

The newest mechanical method of rifling barrels is accomplished through a process called hammer forging. Hammer forging produces a type of rifling called polygonal rifling. A hardened steel mandrel is produced with the shape of the rifling formed on its outer surface. The mandrel is inserted into a barrel blank and the outer surface of the barrel is machine hammered. The hammering forces the barrel material down against the mandrel and the inner surface of the barrel takes on the shape of the mandrel. The mandrel is then removed from the barrel and the outer surface of the barrel is cleaned up. Just as in the other types of rifling, polygonal rifling can have different patterns. The most common polygonal patterns are 6/right and 8/right. This form of rifling is used by Glock, Steyr, IMI, and a few other manufacturers.

 

[Vern Humphrey]

Hammer forging produces a type of rifling called polygonal rifling

Hammer forging can produce a type of rifling called polygonal rifling. It can also produce conventional land-and-groove rifling.

 

[JohnMcD348]

I've never shot a newer conventional firearm with a polygonal barrel but I have shot my Uncle's Whitworth alot over the years and never had much of any real problem with it. It is a BlackPowder rifle shooting a large cast lead projectile. It was used for years in the British army and later by the Confederacy as a sniper rifle of sorts. Granted the BP doesn't push the bullet out at the same speeds that newer powders do but the cast lead is also a bit softer than what you normally get in a jacketed metalic round.

Or I could be totally off on this. I'm far from an expert in these things.

 

[Gewehr98]

Jim, not to disagree with you...

But my understanding of the term "polygonal rifling" was that it was a polygonal bore cross section that continuously rotated to create the rifling at the given rate of twist. In other words, there's a polygon shape there, but only at a given "slice" of a barrel's length. That polygon rotates from breech to muzzle.

I've heard from both camps regarding Glock and other polygonally-rifled firearms with respect to lead bullets. More often than not, the answer that pops up is that they're more prone to leading than traditional land and groove barrels, be they cut rifled, button rifled, or hammer (mandrel) forged.

I won't run cast boolits in my polygonally-rifled and gas-ported Desert Eagle, but I'm sure somebody else would.

 

[Jim Watson]

G98,

a polygonal bore cross section that continuously rotated to create the rifling at the given rate of twist. In other words, there's a polygon shape there, but only at a given "slice" of a barrel's length. That polygon rotates from breech to muzzle.

is so, but it also applies to any rifling shape. Land and groove rifling has an established cross section that rotates along the axis of the barrel to form the helix of the rifling.
Ever see a Lancaster oval bore? The cross section of the barrel bore is an ellipse that rotates to spin up the bullet. The eccentricity of the ellipse is low enough that you have to look hard to tell it from a straight cylinder shotgun barrel.

MY point, and Archie's, is that the high school plane geometry polygon is made up of straight lines, which are lacking in the Glock cross section.

By the way, John, I don't think the British Army ever issued a Whitworth. They were more expensive than .577 Enfield Minie ball guns and were soon obsoleted by breechloaders.