[rich636]

Hey gang,

I recently loaded some rounds for my GP-100 6"bbl using 158gr LSWC from "Houston Bullet Co." over 4.5gr of W231 for ~850fps. The leading was so bad that when I used the spiral bore brush, big shavings and curls of lead were coming out. The more I brushed, the more lead I got for about 30 or 40 passes.

The lead alloy is the very shiny hard sort, can't scratch it with your nail. Ironically, the very soft Speer lead bullets don't lead this barrel at all. Now looking at the loaded round, the only thing I notice that could be my error is that the case has just enough crimp to bring the mouth back straight after belling.

Any guesses why harder lead would lead the barrel?

http://img213.imageshack.us/img213/5056/158ss0.jpg (http://imageshack.us)

[Bula]

My guess is the charge isn't allowing that hard cast bullet to obturate to bore dimensions. If they're really hard, try pushing them a little harder. Also make sure they're sized right for that pistol. Drop one through each of the cylinders and it should not slip right through. They may be too small ie. sized to .356 and not the standard .358 for cast projectiles.

[Bad Flynch]

Leading with hard bullets is just as common, or more so, than with soft bullets. Let me explain.

Bullets that are smaller allow hot gas to escape past the bullet and the hot gasses produce gas cutting, thereby starting leading. This is true for soft and hard bullets, but sometimes soft bullets can bump-up to size and fill the gap. Measure your bullets and your cylinder throats; the bullets should be just as large as the cylinder throats and some larger does no harm. If your sizing dies produce cases that are very tight, the tight cases can resize a larger bullet as it is seated in the case and produce the same problem.

Bullets that have hard lubes sometimes lead from insufficient lubing at low pressures and velocities, particularly if the bullet fit is less than ideal. Most modern bullets have a very hard, high melting point lube; it is so because that stuff stays put well during shipping and handling. However, the hard stuff does not work well a very low pressures and sometimes performance can be improved by shooting them hotter. Sometimes adding Lee Liquid Alox to the bullets will stop this also.

Many revolvers have a bore constriction where the barrel goes through the frame. That is caused by the manufacturer screwing on the barrel so tight that the threads produce the constriction. This will cause leading in the barrel in that area, just beyond the barrel forcing cone. The cure is to lap the barrel to remove the constriction.

If your cylinder throats are undersized for the groove diameter, the bullets will be undersized relative to the grooves and leading will result from the gas cutting at that point. A new barrel or reaming the cylinder throats will fix this one.

Occasionally one sees leading that starts in the barrel's forcing cone. This is caused by an incorrectly dimensioned forcing cone and can be corrected by a good gunsmith. Perhaps the forcing cone is only rough, then polishing the forcing cone would solve the problem.

If the leading starts further down the barrel, then one should suspect that the bullet ran out of lube. This is rare, but can happen with single-groove bullets, bullets that are lubed by coating, and very long barrels. This phenomenon is relatively rare and it is more likely that accuracy will appear from too much lube than this type of leading from too little.

Another thing: sometimes, but by no means always, all of the problems caused by these defects can be lessened or eliminated by using grease wads. They are also called grease-cookies or base-wads. That is simply a thin beeswax disk placed at the bottom of the bullet. Occasionally they work wonders.

One can also add Lee Liquid Alox to bullets that are already lubed. It does no harm and can sometimes help a situation caused by insufficient lube.

Hope that helps.

I had a Ruger GP-100. I think that they are made to shoot jacketed bullets. Ruger uses a long, 5 degree barrel forcing cone and because of past history, Ruger screws their barrels on tightly. I really never did get the gun to shoot lead bullets well, with the exception of the Remington 148 grain HBWC, and then only after reaming the cylinder throats. I eventually sold the gun and replaced it with another that was less fussy about what it shot.

[Walkalong]

Switch to a softer bullet and see if this cures your problem for a couple of reasons already put forth. If it does not, then you will need to get you throat dimensions, bore size, etc & go from there. .38 Spl. runs at low pressures and needs a soft to medium hard bullet. Wax gas checks or Super grex will also solve the problem, but are a pain.
If the leading was mostly in the throats, forcing cone, and first part of the barrel the bullet is too hard and not obturating to fill the throats like Bad Flynch said. The hot gases pass by the bullet at high velocity and "cut" the lead off the bullet, depositing it in the areas put forth already. He is right about the running out of lube part as well.

Just backing up what Bad Flynch put forth. He described how leading with too hard a bullet occurs very well.

[rich636]

That's some great insight guys. I'll try pushing them a little harder first, maybe closer to 1,000fps and see if that helps or hurts. If not then I'll try some plated or jacketed bullets, or stick to the Speer HBWC which seem to do well at low velocities.

Thanks
Rich