Supposedly a major cause of firearm
Kabooms! this "
common knowledge" is actually a myth. A
myth that has caused many a
pistolero to shun this extremely cheap source of
practice ammunition, ignorantly (albeit just cautionarily) wasting a lot of money on
jacketed ammunition for practice use.
Note that for carry or self-defense purposes a
JHP that reliably feeds and fires in one's gun should be used unless one has special requirements like
armor piercing for well protected targets or
frangibles to reduce risk of over penetration.
This myth most likely started after a number of people destroyed their glocks after shooting a round that produced excessive pressure. The theory was that the lead built up too quickly in polygonally rifled barrels and was in effect obstructing the path of the fired bullet. Although it is true that lead does build up faster than jacketed ammunition (in both conventional land and groove and polygonally rifled barrels) thoroughly cleaning the barrel every 100 rounds is enough to keep shooting lead in polygonally rifled barrels safe. Another method is to fire one jacketed bullet for every 10-15 rounds of lead to remove the build up. With this method, one can safely fire 200 rounds of lead in between bore cleanings and still keep pressures within safe levels.
After a shooting session with lead, clean up using Ed's Red or some Hoppes #9 to get all the gunk out. Lead ammunition is a bit more dirty compared to jacketed rounds as aside from powder and primer residue, there is the matter of lead and lubricant residue to take care off. Pay attention to these details and you will be rewarded with the most economical ammunition money can buy.
And since lead is softer than copper, with proper care your barrel will last longer than if you exclusively used jacketed ammunition.
This information is the result of personal tests on a HK USP 45 F which, like the glock, has a polygonally rifled barrel.
Update February 24, 2002 - While lead is ok
just as long as you don't forget to shoot that fmj every 10 rounds or so copper plated lead is evil. I tried just a mag of those and ended up scraping metal fouling out of my barrel with a screwdriver. Of course i got stupid and forgot to do the fmj every so many rounds of lead.