First post here. A friend of mine has built himself a fantastic break-action rifle from scratch and we're looking into the options of chambering it in 40-65. Since that chambering is not a SAAMI approved one, there are dozens and dozens of reamer designs for it. After reviewing several chamber prints, it looks like we may as well design our own reamer. Although I’ve designed several wildcats for the AR platforms, I’m very new to cast bullets and I realize there are a lot of nuances to cast bullets as it relates to chamber spec's that will enhance or degrade accuracy. This rifle is to see a moose hunt later this year and the chamber spec’s are being driven by that – middle of the road bullet weight, #2 alloy, flat meplat, gas checked, smokeless powder, 25-30k psi. Following are the trending thoughts I have and I welcome any input you're willing to offer that will help us specify the best dimensions/approach to consider:
- His bore slugs out at exactly 0.408"
- we’re considering a chamber designed to use re-sized 45-70 casings versus one that uses the one source of 40-65 brass (Starline) (pros/cons of either option anyone???)
- the bullet we're warming up to is the Accurate Molds #41-340JG, in #2 alloy, which is a 0.410” dia., gas-checked, 340 gr RNFP, and we would marry it to a Gator 0.416 rifle caliber, copper GC., The large, flat meplat is looking superb for driving a large permanent wound cavity and #2 alloy seems about right to keep it functional as such
- swaging said bullet/GC down to 0.4085”-0.409”
- cut the freebore diameter to 0.409” (or would it be best to keep closer/at 0.408” groove diameter???)
- cut the freebore length to have the seated bullet just into the lands
- cut the mouth-to-freebore transition at 30deg and with a small “ADS” radius (anti-dounut-slicing :-) ) at the small diameter edge
- cut the leade angle at 1.5deg (is that optimum for cast?)
- cut the chamber neck diameter 0.0015” over loaded cartridge neck diameter (is that too tight for cast bullets?)
- cut the chamber length so that the resized 45-70 brass needs to be trimmed at least 0.050” (preventing short casings)
- neck size only with a Lyman M die tuned for bullet our diameter and FLS/anneal when needed
- find a 40-65 die set that has been designed around 45-70 casings, has a straight neck section (hopefully), buy them, size a few brands of 45-70 brass and determine the body dimensions of the reamer based off that. Anyone have any insight as to which dies that would be?
Any insight anyone is willing to offer is appreciated.