Since the 180 gr. bore riding GC shot decent even though it was a "bastard" design, I want to try some more bore riding designs, so here's a couple of new bullets to play with, er, I mean test.
The new bullets have a crimp groove in the right place even though I'm not planning to crimp them. If nothing else the oversize crimp groove acts as a shock absorber when the nose slams into the rifling.
The bore riding section was made longer with the hope that it would not have to jump so far to contact the rifling, but I will show later how that did not work as planned.
The front band length was chosen so that the front band would nearly make contact with the cylinder's ball seat when the cartridge was chambered, and that did work out.
The bore rider drops out of the mold at 0.3474"+ but then the coating brings it up to 0.350"+ depending on how thickly you apply the coating -- I aim for 0.001" thick but don't always hit it. At this point I don't know if 0.350" it the optimal diameter.
Previous tests with different bullet weights showed that accuracy improved as weight increased up until 180 gr., then remained the same with 190 gr. and 200 gr. bullets, but just to cover all bases I'm going to try a 220 gr. bullet.
I went with a bevel base because that's what the 180 gr. BB control load uses. So far the coated BB bullets seem to be just as accurate as a GC in this gun, but that may be because I haven't been pushing the BB that hard. If these BB bore riders work well then I may try GC designs, too.
If you drop a sized bullet into the chamber it comes to rest like this, with the front band making contact with the ball seat. The chamber throats are 0.3580" and I size the bullet in a 0.358" die, but due to spring back the bullets end up 0.3583"+, so they can't be pushed through the throats with finger pressure contrary to the popular rule of thumb that I have rarely followed (about 0.0005" clearance is required to push through without force). The nice thing about the bore riding design in a revolver is that when properly done it results in this perfect fit yet chambers reliably without having to do any fancy nose sizing.
As mentioned earlier the hope was that the longer bore riding section would grab the rifling in the forcing cone, but instead the front band is the first thing to make contact with the forcing cone. That's because of the very gentle 1.3 degree leade angle. If I had to do it over I might go with a 3 degree leade angle, but oh well.
If I cut the bore rider oversize, say 0.355", then it would probably make contact with the rifling before the front band. Maybe I'll try that eventually. As I said before, at this point I don't know which diameter is optimal for the bore rider. Cast bullets don't always behave the way we think they should behave so sometimes all we can do is try different things and let the gun tell us which works best.