I shot my second load of cast boolits recently, these were 158gr flat points sized to .358 in a Ruger GP100. This went better than my last adventure with my 1911 because the boolits were not significantly undersized due to an inexperienced caster not realizing he wasn't getting good fillout
I had far less leading than I had with my 1911, but there was still some. Not excessive, I can clean it in about 10 minutes. Most of it gets concentrated in the forcing cone in the area just before the rifling starts. There was some leading in the first short bit of rifling, but not much. There was a good bit of persistent crud maybe 1/4 to 1/3 the way down the barrel stuck on the rifling. I don't *think* this was lead, but I'm not 100% sure. It looked more like powder residue, and I wonder if it kind of combined with burned boolit lube...I did kind of go a little overboard with the 45 45 10 this time.
The leading was, however, enough to impact accuracy negatively.
I have slugged my cylinders at just a tinge over .357 (they run .3572 to .3575). I don't know the exact dimension of the forcing cone short of the rifling, other that I know a .358 boolit will pass through it easily enough until the rifling is engaged. The groove diameter of the barrel is right at .357, almost exactly.
My max load was 4.8gr of Win231. I worked up to this increments as usual. The work up loads leaded the same as the max load. This "max" load is not by any means a powerful load, I just didn't think I needed to try to run magnum level pressures my first time out.
My boolit is a 158gr flat point cast from a Lee mold (358-158-RF). It was cast with wheel weight alloy (hardness should be between 8 and 10 BHN). All boolits were sized to .358 and tumble lubed with 45 45 10.
So my question is, what are the unique challenges to revolvers that can cause forcing cone leading? Looking for my next corrective step here. If the boolit isn't obturating well, that would indicate I need a heavier load or softer alloy. Or maybe .358 is undersized for my revolver? It's only half a thousandth over the size of my larger cylinder throats. Maybe it would be worthwhile to try to shoot them unsized in this gun? (My mold is dropping them between .358 and .360, slightly larger than what I get after sizing).