What is the point of Glock polygonal rifling?

Also, this is a Glock (and maybe Kahr) issue. No other polygonal maker has these concerns.
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According to who?

The manuals for the HK USP and P30 both say not to use lead bullets too(I can share pictures of the page if you want). It seems to be a common stance among all manufacturers of polygonal barrels.

Similarly, the HK manuals also recommend against using steel or aluminum cased ammo - but this is just for reliability standard. In general they recommend using high quality brass cased rounds with copper jacketed bullets.
 
The manuals for the HK USP and P30 both say not to use lead bullets too(I can share pictures of the page if you want).
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Here's the manuals for the USP and P series. These are directly from HK USA, and USP manual shows a revision date of 2007.

http://www.hk-usa.com/-images/shared/USP Manual REV 3-07.pdf
Page 12 for ammunition.

http://www.hk-usa.com/-images/shared/PSeries_Ops_Manual_060809.pdf
Page 17 for ammunition.

You can also look through a PDF using Ctrl F to look for the word "lead".


So whatchu talkin' about, Willis?
 
Just curious, but can anyone cite a warning from Glock saying specifically that firing lead ammunition will cause a lead buildup and lead to blown up barrels/guns?

NOTE - Not some general caution about firing lead bullets, or firing reloads, but a specific caution or warning about lead bullets causing lead buildup and blown up guns. And from Glock, not from some internet guru or anonymous source.

Jim
 
http://www.hk-usa.com/-images/shared...ual_060809.pdf
Page 17 for ammunition.
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Yep... Just like I said...


"Use of cast-lead bullets is also not recommended."



Yes.

Originally Posted by Glock USA
Can I use lead bullets?
No, we recommend the use of jacketed ammunition only.
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http://us.glock.com/customer-service/faq
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Not at all what he asked... Let's look again:

Just curious, but can anyone cite a warning from Glock saying specifically that firing lead ammunition will cause a lead buildup and lead to blown up barrels/guns?

NOTE - Not some general caution about firing lead bullets, or firing reloads, but a specific caution or warning about lead bullets causing lead buildup and blown up guns. And from Glock, not from some internet guru or anonymous source.
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Your quote does not in any way say that the reason lead is not recommended is due to blowing up the barrel...
 
OK, whoopee do. Manufacturers of many, perhaps all, polygonal barreled pistols recommend against the use of cast bullets.

SO WHAT ? No one here has still addressed the FACT that many of us DO use cast....with NO PROBLEMS whatsoever. All we hear are a bunch of vague warnings, based on reading an owners manual.....followed by a bunch of assumptions NOT predicated on ANY personal knowledge of anything. Are you guy(s) just completely without any imagination....or just too bloody stupid to know the difference ? You completely dismiss the concept that ANY PORTION of the reason for these vague warnings COULD involve precaution....when fear of liability governs a large part of the actions of every manufacturer these days. You don't get that these manufacturers will ALWAYS err on the side of caution, where potential liability exists ? Really ?

In any case, none of you have a shred of proof, let alone any plausible explanation for why, if using cast bullets is automatically so dangerous in polygonal barrels....that many of us use them very successfully. You can't explain it and you can't refute it. ALL you can do is sit on the side and whine "but the book says so !" So, get over it.
 
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Like how many rounds of lead were shot through those particular barrels before they failed?
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That's precisely the problem. Testing showed that it was virtually impossible to come up with an accurate general rule of thumb for how fast the leading progressed and how many rounds could be fired safely.

In one test, two identical Glocks using identical ammunition showed dramatically different effects from leading. One gun showed twice the effects after 75 rounds that the other gun showed after 300 rounds.

That means that one of the guns was leading up at a rate of 8 times faster than the other gun even though the ammunition was identical and the guns were apparently identical.

In practical terms, this means that while one Glock may not show any unusual leading, another one that appears to be identical to it and that is using the same ammunition can have a buildup of lead in the bore that creates a dangerous situation even though far less ammunition is shot between cleaning intervals.

There's solid information out there for people who want to really know the score. There's a book called "The Glock in Competition" that contains a chapter written by a forensics engineer (Mark Passamaneck) who has studied the topic exhaustively. That chapter covers Glock leading issues in detail. His results were confirmed by Glock.

Unfortunately, many people are far more concerned with winning the argument than in being informed. So the pressure measurements and investigation results haven't put an end to this debate like they should have.
In any case, none of you have a shred of proof...
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False.
...let alone any plausible explanation for why...
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Also false. Both plausible explanations and proof are available.
...if using cast bullets is automatically so dangerous in polygonal barrels...
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It can be done without causing the gun to blow up--people do it on a regular basis. The problem is that there's not an accurate rule for how to do it while insuring safety. Basically people who do it are running a risk and there's no way to know for sure if that risk will catch up with them or not because there's no accurate recipe for how to do it safely.
...that many of us use them very successfully.
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Lots of people do risky things successfully on a regular basis, that doesn't mean the risk doesn't exist, it just means that not everyone who takes risks bears the consequences.
 
Uncle Malice,

Thank you, I had missed that in the P manual. It isn't really a prohibition, and isn't found in the USP manual at all. Nor is a similar "not recommended" language in any of the other guns I posted.

And I did not satisfy James' request, but does anyone expect Glock to publish a detailed admission? They are unequivocal about no lead. Not a mere recommendation.
 
The thread title makes this about Glocks

Its a Glock... so why not just take 30 seconds every box or so to pop the barrel out for a good look-thru to check for build up?
That'll pretty much eliminate any risk...

Question... Does anyone know if chasing cast rounds with the occasional fmj has any cleaning benefit?
Will any of the lead stick to the copper as it goes by?
 
Its a Glock... so why not just take 30 seconds every box or so to pop the barrel out for a good look-thru to check for build up?
That'll pretty much eliminate any risk...
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The nature of the Glock rifling can make it difficult to detect leading buildup, especially under range conditions.
Question... Does anyone know if chasing cast rounds with the occasional fmj has any cleaning benefit?
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If there's any really significant leading and you chase it with a jacketed round, you're tremendously increasing the chance of an "incident". I've seen one report of a Glock 19 blown up by following 50 rounds of lead bullets with a single jacketed round.

By the way, that's not an issue specific to Glocks. Beretta warns that one should never shoot a jacketed round through a bore that has been used with lead bullets until the bore has been thoroughly cleaned of lead. Allan Jones, formerly of Speer, et. al. warns against the practice as well, citing several guns he has seen damaged or destroyed by it.
 
Question... Does anyone know if chasing cast rounds with the occasional fmj has any cleaning benefit?
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This is the old "shoot the lead out" theory. It don't work. It can increase the pressure to dangerous levels.

Decades back S&W introduced the Model 19 K frame revolver in .357 Magnum. The intent was to have a lighter weight revolver that law enforcement could shoot their practice 38 Spl. loads in and carry .357 on duty. The concept worked well till Super Vel introduced a jacketed hollowpoint round with 125 and 110 grain bullets at 1400 or so fps. Folks who did not clean the lead fouling from their barrels found that the jhp bullets did not "shoot the lead out" but did crack forcing cones just fine.

Ah well, live and learn. Be sure to blame the gun for whatever happens.

tipoc
 
enough

IF I had to shoot lead bullets in a poly-Glock I would check its bore (and clean it) every 50 rds.

Not joking.

I have some experience with Glocks.
 
I think Glock's purpose for its polygonal barrels is both for reliability and accuracy. With polygonal barrels Glock can make the slide-to-barrel fit a bit looser for reliability (think 1911 military) but at the same time make up for any loss in accuracy through polygonal barrels. Brilliant concept guys-one reason I never buy aftermarket barrels for my Glocks. This way my Glocks are both reliable and accurate.
 
With polygonal barrels Glock can make the slide-to-barrel fit a bit looser for reliability (think 1911 military) but at the same time make up for any loss in accuracy through polygonal barrels.
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The type of rifling has no impact whatsoever on slide-to-barrel fit.

As far as accuracy goes, I'm not aware of any data that demonstrates that different types of rifling affect accuracy in any significant way. Typically there are claims that some kinds of rifling are more durable, offer a tighter gas seal or are easier to clean, but barring pathological cases, they should all deliver the same accuracy, all else being equal.
 
John,

He's not saying they are related, just that Glock is substituting a more accurate component (barrel) to make up for accuracy reducing loose slide fit.

But I agree that polygonal barrels aren't necessarily more accurate. However, I've never heard of an inaccurate polygonal barrel. Polygonal barrels are mandrel forged to shape, and have none of the potential accuracy issues associated with poor crowns, two piece construction, etc.


I wouldn't say that all Glock's necessarily have loose slide to barrel fit. The old ones weren't tight, but fit reasonably well and would often produce groups pretty much like USPs and Sigs. More recent guns might be sloppier, but not by design. My '94 G19 fit together crisply.
 
If polygonal rifling was more accurate, you would see the benchrest crowd using it to put multiple bullets through the same hole. A premium barrel is of utmost importance to those guns, but I haven't heard of any serious competitors using a poly rifled gun. There may be some, but their existence is not evident.
 
I can't prove it, but I think that polygonal rifling has an advantage in manufacture. Many big manufacturers use hammer forge rifling for mass production because it is fast and therefore cheap once you have the big machine paid for. It looks to me like the rounded contours of "polygonal" rifling would give a stronger, longer lasting hammer forge mandrel, than one made for conventional "land and groove" with its multiple square corners to get beat on.
Obviously the savings is small, there are a lot of hammer forged "land and groove" barrels out there, but when you are equipping an army or 70% of the police departments in the US, a small savings per barrel really mounts up.

And a "land and groove" barrel is just as polygonal as anything from Glock et al. Consider a six groove barrel that has six groove bottoms, six land tops, and twelve groove side walls. Let's see, 24 sides, that makes it an icosikaitetragon. (Had to look that one up.)
 
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