from the old forum, perhaps posted by BAbore ??? :
I finally got my 1895M 450 Marlin rebarreled, lapped, and a chamber cast done. Now it's time to get serious on a mould. Here's what I got.
I also saved my AutoCAD drawing as a bitmap if you can't see this well enough. Don't quite know how to post that though.
Before I fire lapped the bore it had constrictions of 0.001". A full push through sinker was 0.4571". A muzzle slug measured 0.4581. The bore was extremely rough prior to lapping. A full push through slug now measures at 0.4583". Group size went from 1 1/4"-1 1/2" at 100 yards to basically one hole. My first ten bore conditioning shots went into 7/8" at 75 yards with five complete cleanings. So now I'm ready.
Looking to design a 420 gr OFP bullet with a 73% meplat, Hornady step shank and most likely two driving bands with a 0.8 or 0.9 ratio. The nose length and front driving band are what I would like some help on. The chamber cast looks to have an extra 0.137" in length before going into the leade and throat. I also have to contend with the 2.55" OAL. Any good suggestions.
I forgot to mention. The 0.4595 dimension, on the chamber cast drawing, is just where the throat ends. not farther out.