I decided to do some playing this winter and shoot some bullets into the snow. The bullets shot were the Lyman "Keith" 358429 sized .358, lightly taper crimped on the front drive band to an OAL of 1.638 (to fit my GP 100 cyl). Load was 14.9/wc820/CCI SR primer and clocks about 1260 FPS out of my 6" GP. The top row of bullets was pure lead, the next was ACWW and the bottom row is a 50/50 WW/lino mix air cooled.
As you can see the acceleration forces on the pure lead Keiths turned them into FPTC's BUT they did not lead the barrel at all and as you can see did not skid on the rifling. Bases were badly distorted I think by either muzzle pressure or at the cyl gap. They left a slight bit of molten lead at the edge of the forcing cone. When shot at a 25 yd target 2 or 3 would hit together in about an inch with others 2 or 3" away. I'm guessing the flyers were ones with blown bases as they don't strip on the rifling.
Acceleration forces also show up on the ACWW in that the nose sets back slightly closing up the crimp and lube grooves along with bases showing some slight distortion but not bad. From previous accuracy testing ACWW's will average 2.7" at 50 yds for five 5 shot groups. Water dropped WW do no better.
The 50/50 bullets show no setback and have the most square bases of all the bullets. Again from previous accuracy testing with more than five 5 shot groups at 50 yds they average 1.9" groups. My wc820 tracks exactly WW296 so I'm guessing this load is slightly north of 30K PSI. Just thought I'd share with the board.