My Ruger GP100 Match Champion and other related topics...

I've been active (sort of) on the forum for several years, and I find it to be a great source of experience, information and ideas! Now, I am in need of help!

Nice Gun! :smile: I have polished it a minimal amount, and installed a 12 Lb. mainspring and 8 lb. return spring.
A .358 minus pin gage fits all cylinder throats, with a little oil and gentle persuasion, so, I believe that .358 sized bullets should be the proper ones for my revolver. Would a .359 sized boolit cause problems? A .356 minus pin gage will not fit into the muzzle.

I don't cast any more, so will need to purchase commercial cast/swaged/plated boolits.

I bought some "hard cast" 158 gr. BB SWC from a local caster, and experienced leading in the first 1-1 1/2 in. forward of the forcing cone, which is a problem I had not had before. Someone mentioned that the bullets may have been too hard.(?)

During the years I shot IPSC, casting my own 150 gr. RCBS SWC boolits on a Coleman stove, I never had a leading problem, using alloy as close as I could come to the Lyman #2, with Lee's old sticky red pan lube.

Now; I like square based boolits, and most of the commercial casters nowadays only offer the bevel base, which makes casting easier. Does it make any practical difference with leading, or anything else?

Next, Lyman #2 alloy is about BHN 12. iirc, and most casters' offerings are about 16 BHN or higher. Is that factor with leading?

Even though I have a 357 Magnum, my loads will be held to a max of 38 Spl. +P velocities for shooting enjoyment. I'll be using 125 gr practice boolits, loaded to duplicate the recoil impulse of my carry ammo, which is Speer Gold Dot 38 +P Short Barrel. I'll also be loading 148gr. full wadcutters, and 158 gr. SWC , Speer swaged SWCHP or J-word boolits .

Are there any words of wisdom regarding loads, boolit manufacturers, hardness, etc. or...would it be a better idea to just go totally with plated projectiles?

Thanx!

.358 or .359 will work. Lead bullets are generally soft even that anything that'll chamber will get squeezed down easily enough that it won't cause problems.

Leading is a function of fit, using the correct alloy and using the correct lube. If any of those are wrong you can have problems. Coated bullets are more common now than they were previously. This helps prevent leading in a number of applications. There are a couple vendors in the swapping and selling section of this website that have good options for purchase. I typically use flat base bullets. Bevel bases are supposed to be easier to load since they start into the case easier.

You may want to try switching lube on your purchased bullets or giving them a tumble in LLA to supplement the existing lube to see if that helps.

It should not be surprising a .356” pin gauge will not get in the muzzle as the rifling gets in the way. Pin gauges are only capable of measuring the bore diameter of a barrel, which is the distance from rifling land to rifling land. Pin gauges cannot measure the groove diameter of a barrel and there is no use trying to do so with them.

You will need to slug your barrel to get the true bore diameter.

[quote

You didn't mention the load or velocity of your ammunition. Try shooting some of those bullets around 800 fps and I'll bet the problem clears up. Then you can work your way back up, and diagnose along the way.