In need of experienced casters advice

[Slinger]

I've got a 45 Colt in a 5-1/2 Blackhawk. The is super accurate using the RCBS 255 gr. SWC.@ .452". I bought a Lyman 452460 255 gr SWC mould. Had to send it back as it was dropping slugs @ .450". They recut it & It now drops them @ .455". I size them to .452" What I ran into today was using a load of 9.2 grains of Unique/Federal primer, Jake's purple lube, I was getting leading with my #2 alloy, but when I used straight wheelweght alloy It was fine other than a little skidding ahead of the forcing cone. My question is WHY? I would think it would lead with the W-W & not the #2.................. 7.0 gr of WW-231 shot o.k. with the #2 but threw them with the W-W. I noticed that there was a section of the middle drive band that was undersized as I saw it after sizing the W-W slugs. The #2 alloy boolits did not show the undersize section. Need your input guys. I'm thinking I'm going to send the mould back and have them replace it. It's on the high end of diameter and I'm thinking may not be concentric on the center band. On the other hand, the Unique load/W-W alloy put 8 shots into 1-3/8" @ 25 yards off of bags.

[jonk]

I would guess that the wheelweights are slightly softer; that the number 2 has a little more tin and antinomy. Sometimes a bullet can be TOO hard, particularly in a handgun, and doesn't obdurate properly leading to blow by and leading.

[jdgabbard]

I've had more leading with harder and/or undersized boolits then I have with Pure and softer alloys.

[jforwel]

Have you measured your chamber throats? With the harder alloy you may need to size your boolits at .453 or .454 to get them to leave the chamber centered.

[Slinger]

Have you measured your chamber throats? With the harder alloy you may need to size your boolits at .453 or .454 to get them to leave the chamber centered.

Throats are .4515" Max. is .452" on a couple. Bore is .451" A slug sized .452" will not go thru any of the throats. I shot the RCBS 255 gr. SWC in 11BHN & 14BHN and didn't get leading like the Lyman boolit. Side by side, the two are noticably different in body & nose config. The RCBS shoot both BHNs and both loads with accuracy & minimal leading (ahead of the forcing cone mainly) They don't make a .453" sizer die for the Lyman.

[deltaenterprizes]

Jonk has the answer.

[Slow Elk 45/70]

Yes, Harder Boolits need more pressure to up-set them into the barrel and seal against gas-cutting, Harder boolit, push it faster. I would size to .454 if I was going to size them. Also , Rugers like Large Boolits , I think you are oversizing your boolits.IMHO