Are Lead Bullets Really A Problem With Polygonal Barrels?


April 20, 2009, 11:27 AM
I have an HK P30 9mm that has a polygonal barrel instead of standard riflling grooves.

I have never fired lead bullets through it due to reading about some problems with bullets seriously fouling the barrel.

I would like to reload with some lead bullets, but need to know if this problem really exists, or is it an old wives tale?


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April 20, 2009, 11:32 AM
It is real with soft commercial bullets.

Not enough rifling to get a grip so they skid and deposit leading.

I shoot pure Linotype cast bullets in my Glock barrel with no problem a tall.


April 20, 2009, 11:48 AM
What about the ones from Missouri Bullet? I see where they are quoting specific hardness levels.

I wonder how their hardness compares to the soft commercial ones?

April 20, 2009, 12:22 PM
Seems to me that if the bore is slugged and the cast bullets are sized .001" ~ .002" over "groove" (for want of a better word) size, there should be no skidding or leading.... assuming a good lube is also used.

I have a CZ-82 and an RCBS 100 grain Mak mold so the next time I cast, I'll give it a try.

If you do have a leading problem, a tight wad of fine steel wool on a jag will take out lead deposits like nobody's business.

April 20, 2009, 02:19 PM
I fired about 3500 cast bullets through a Khar 9MM with their polygonal barrel that I used to own. Accuracy was very good and leading was very minimal using air cooled wheel wt metal and water dropped wheel wt metal bullets. I sized my bullets to .357 and was shooting mostly close to max loads with 121 gr. bullets.

April 20, 2009, 02:44 PM
It is not the leading problem in the polygonal barrels, it's the extreme pressure created by this leading that will cause the trouble and could possibly lead to a blown gun. Just remember a poly framed receiver is no where close to the strength of a steel receiver and will let go in pieces under extreme stress from the barrel pressure . I did see a Glock 17 blow at a local IPSC shoot less than two years ago. If you want to shoot lead. go ahead, just replace the barrel with one of conventional rifling. :uhoh:

Steve C
April 20, 2009, 02:49 PM
Polygonal barrel lead up something terrible. You won't see the leading looking down the bore but run a lead wipe patch down it and you'll see it or look at the barrel from an oblique angle so you're looking at the barrel wall and not out the muzzle and you'll see it too.

Stick with jacketed bullets if shooting from a polygonal barrel or buy an aftermarket conventionally rifled barrel for lead.

April 20, 2009, 03:00 PM
No problem using HC lead in my H&K USP .40S&W. Just clean after each use.

April 20, 2009, 07:55 PM
I've had good luck with cast bullets and Glocks/H&Ks. Monitor your weapon, check the barrel after 10, 20, 50 and 100 rounds, see what it does. If it leads, change something. In my experience, they work fine.

April 20, 2009, 08:11 PM
It's all BS. I shoot nothing but Missouri bullets in my Witness Match Poly barrels, never a problem with leading. The right size bullet and good lube is the answer.
Flame away!!!

April 20, 2009, 08:22 PM
I shoot lead in poly barrels. Marlin uses poly on their lever rifles, cz-82s are poly, HK's are poly, glocks are poly. . . even if you get leading - so what? clean it. I've shot a LOT of cast through a few stock glocks with no issue, and a cz-82.

April 20, 2009, 08:55 PM
I got my polygonal barreled 40S&W’s when the
Urban Legend ”lead bullets cause polygonal-barrel KAGOOMS”
was being wildly bantered about on many forums, with very little truth to the mix. Before reloading lead, I did extensive research and discussed the problem with some well known gunsmiths and the Glock people at the SHOT Show. Both sphincters on every Glock staff were tighter than a bull a$$ at fly time. Nice folks, but NO HELP THERE! But they did make a valid point. Glock pistols are tremendously popular, and by shear weight of numbers you will have more “supposed problems” (their words).

There was no single factor that caused the problem; there were combinations of contributing factors. The shortest oversimplification is, “Glock KABOOMS were most commonly caused by lead buildup which could have been avoided with frequent inspection and cleaning of the chamber and barrel.” Just how often is frequent??? Every 100 rounds is anal, every 200 rounds is prudent??????? Hell, I’ll err on anal until I get some data to increase or decrease.

Unsupported Chamber - Glock started with loose chambers with a small grove at the rear in the 6 o’clock position, thus the case was not touching anything at that point, it was unsupported. If the pressure is sufficient and/or the case weak, then it will either expand into the unsupported portion of the chamber or will rupture.
Firing Out Of Battery - Means the weapon will fire when the slide is not completely forward; therefore, the cartridge brass is not properly head spaced against the front of the chamber. Glock violently denies their weapons do this. However, everyone I know with an older Glock will tell you they do.
Lead Bullets – the lead needs to be at least a Brinell hardness of 19. Velocities should be kept under 1000fps.

So what causes the KABOOMS?????? The common factor of kabooms was usually case failure, and most of the failures were with reloaded cases. But remember that factory rounds cause good numbers of KABOOMS every year as well.

Glock’s research of KABOOMS showed a build up of lead at the point of head-spacing. This caused the cartridges to be progressively set farther back in the chamber farther and farther as more rounds were fired. The design of the older Glocks allowed them to fire (fire out of battery) these rounds which were set back. If the pressure were sufficient, the case would rupture.

What factors can cause over pressure????? Obviously an overloaded round will do nicely. Lead bullets will cause leading in the barrel and the chamber. The degree of build up and the number of shots required to reach overpressure will vary wildly with lead composition/velocity/powder/lube and so on. The leading of the chamber in combination with the increased pressure of a leaded barrel can cause the case to rupture. There are lots of other factors, but will not be discussed here.

Shooting jacketed bullets after lead in polygonal barrels is controversial. Does it clean out the lead??? It is theorized that in reality the jacketed bullets irons the lead to a shiny flat coating and the bore is decreased.

Bottom line. Shooting lead in polygonal barrels is safe as long as you use hard cast bullets, check the chamber and barrel for leading frequently, and clean the weapon more frequently than you would with jacketed.

April 21, 2009, 11:59 AM
Early Glocks also had a design feature (Glock Perfection?) that allowed them to fire out of battery by as much as 3/32".

As lead build-up in the front of the chamber increased, it would hold the slide progressively further out of battery, and the damn guns would still fire.

That further un-supported an already unsupported case.


April 21, 2009, 12:44 PM
Forgive the dumb question but what is the difference between a poly barrel and standard rifling?


April 21, 2009, 01:01 PM
what is the difference between a poly barrel and standard rifling?

Standard rifling is essentially two vertical walls connected by a flat top. Imaginer a squared letter "n".

Now run a diagonal line from a lower corner of the standard rifling to the opposite upper corner and remove the top portion. What you have left is polygonal rifling; a slope to a peak and then a sharp fall off. Think of the teeth of a ratchet. In actual practice, it's not nearly so defined as that and the bore appears to be smooth unless the light is right to show the slopes and valleys.

Leading is generally caused by a rough bore or melting caused by the heat of the burning powder. Polygonal rifling should be pretty smooth to begin with and if a bullet is sized a thousandth or two over groove diameter and lubed with a decent quality lube, I see no reason for leading in a polygonal barrel unless too hot a load is used. The next time I cast bullets, I'll make some for my CZ-82 and see what happens.

April 21, 2009, 01:05 PM
Read here

There are polygonal versions other than the one pictured.

April 21, 2009, 01:08 PM
Here ya go.,png,gif


April 21, 2009, 02:15 PM
It's all BS. I shoot nothing but Missouri bullets in my Witness Match Poly barrels, never a problem with leading. The right size bullet and good lube is the answer.
Flame away!!!

Just like floydster said. I talked to a Glock Armorer at a GSSF match and he told me shooting lead in a Glock was not a problem if done right. He said it would usually take a larger bullet, for example a 9mm pistol would normally take a bullet sized to .358. Slug the barrel and see. He also said most problems were caused by people shooting lead bullets all day and thinking they could clean the barrel out by shooting a few jacketed bullets after, bad idea. I have a couple of friends that have shot thousands of lead bullets in Glock barrels without any problems.

April 21, 2009, 04:33 PM
Well, I had an early Glock 20--arguably, the first one sold in the Mps-St. Paul Metro area.

After 200 jacketed rounds, I switched to my lead reloads, carefully-developed for 900+ fps from my 6" Omega. (4.9 gr. of 231 under a 200-gr LTC; CP bullets.) Gun was cleaned; next range trip--at round 284, the chamber split, and the slide departed over my left shoulder. The slide and barrel were massively distorted, but the receiver did hold up fairly well. (I had only a sprained trigger finger and a blood blister.)

It could have been a double-charged case, I know--but to this day I don't think so.

I understand Glock has changed their barrels somewhat since 1996 or so, when that happened. (What day did sick Willy tell us that 'he-did-not-have-sex-with-that-woman'? It was that day.)

Meanwhile, I'll agree about the Witness Elite Match barrel--no trouble with lead in mine, either. Meanwhile, I really do think I woud consider Steve C's comments were I to buy another Glock.

Jim H.

April 22, 2009, 12:25 AM
Marlin uses poly on their lever rifles,

B.S. Marlin uses micro-groove or Ballard rifling. They have never made a poly rifled bore.

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