From: Ed.Harris@p0.f417.n109.z1.fidonet.org (Ed Harris)
Newsgroups: rec.guns
Subject: Re: Polygonal barrels
Keywords: barrel, fouling
Date: 1 Oct 90 21:07:52 GMT

In article <9042@orca.wv.tek.com> rmihara@sandstorm.berkeley.edu (Randall
A. Mihara) writes:

>I was recently reading in a magazine about the H&K P7M13 and noticed
>that it has a polygonal barrel.  They say not to use lead bullets
>because it will "foul" the barrel.  Unfortunately, the range I

The problem is not leading of the barrel, but lead deposits
accumulating in the gas cylinder and on the piston-rod.  The gas port
of the P7 series pistols is immediately ahead of the chamber mouth,
which is about at the region of peak pressure in the 9 mm.  The base of
a soft-jacketed or lead bullet is deformed at this point, scraping off
a piece of fouling which is blown into the gas port.  These particle
build up at the end of the blind hole which is the gas cylinder, and
may preclude full travel of the slide in cycling.  You can remove them
with a reamer HK makes for the purpose, but based on experiences with
my P7 I would not recommend lead bullets at all, and I eventually sold
my P7 because I had problems with pieces of jacket material being
scraped off after about 6-8,000 rounds, as the gas port enlarged
through eroion.  I had HK rebarrel the gun, then when it came back from
repair I sold it and went back to carrying my HP Browning.

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