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Old March 29, 2013, 07:49 PM   #26
TMD
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Quote:
I'm not even sure it's the polygonal rifling that causes the problem. It very well could be a sharper shoulder at the front of the chamber & case mouth that allows the build up of lead particles/shavings during firing, and then starts to push each next round further back, until the cartridge fires from a less supported breech.

Ding! Ding! Ding! Ladies and gentleman we have a winner.

And for those of you who wonder about polygonal rifling guess what, it was around long long before jacketed bullets.
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Old March 29, 2013, 09:50 PM   #27
JohnKSa
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I'm not even sure it's the polygonal rifling that causes the problem.
It's the polygonal rifling. Gale MacMillan, who knew a thing or two about barrels & rifling explained the issue succinctly and his quote is still floating around on the internet for anyone interested in the topic.
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And for those of you who wonder about polygonal rifling guess what, it was around long long before jacketed bullets.
Yes, and there are good reasons why it was never an issue in those days of black powder.

1. You had to clean the gun every few shots anyway.
2. The pressures generated by blackpowder were much lower than smokeless.
3. The velocity/patching/lubrication was such that any significant leading was unlikely regardless of the rifling type.
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Old March 30, 2013, 08:09 AM   #28
rodfac
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I've done some lead alloy bullet shooting in both a G19 and a G23...both leaded terribly after a single magazine. Cleaning wasn't much of a chore after so few rounds...but accuracy was atrocious. The first two or three rounds were good for a little over an inch at 10 yds from a Weaver Stance, slow fire. The remainder spread out to over 4" in an increasing diameter, indicating a progressive leading of the barrel and leade.

Both barrels showed a buildup of lead at the front of the chamber, right at the beginning of the leade and rifling. This buildup after a single magazine of lead alloy bullets was thick enough to feel as I dropped reloaded rounds into the chamber of the dismounted barrel, in effect increasing headspace, ie. not allowing the round to fully seat in the chamber.

Too, the rifling was streaked from breach to muzzle, and lead removed with a patch wrapped bronze brush as well as a Lewis Lead Remover showed long streaks of leading in the bore.

Replacing the barrel, leaded in this way, then trying to chamber loaded lead alloy rounds, I found that full lock up became difficult. What really concerned me was that at some point, I feared the barrel would lock up just enough to allow firing pin fall, with a partially supported case...a prescription for a case blow out.

I do shoot lead alloy through both Glocks now, but with Lone Wolf barrels installed (conventionally rifled and with better rear chamber support for the case head), and I clean them thoroughly. Glocks are justly famous for their rifling, and in my experience, their accuracy with that polygonal rifling type and jacketed bullets, but it wasn't a good match for lead alloy bullets.

HTH's Rod
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Old April 1, 2013, 02:31 PM   #29
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I have a G21 and a Storm Lake aftermarket barrel for it. I cast my bullets from wheel weights, and lube with Liquid Alox. The Storm Lake barrel leads up, and I have to use a Lewis Lead remover or chore boy wrapped mop the remove the leading. The Glock barrel leads very little with my bullets and loads. I get better accuracy out of the Glock barrel than I do with the Storm Lake barrel. I will probably just sell the Storm Lake barrel as the Glock barrel shoots better for me and is super easy to clean.

Just my experience, I'm sure yours will vary.
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