I have a couple of 45-70 single shot conversions and 2 40 cal custom sml"s that I've built over the years. Sold all of my 45 custom builds. The single shot conversions shoot good and are super light and handy. I don't stretch them out so I can't vouch for their accuracy beyond 200 yds. The 40 cal custom guns are very accurate. I took a deer 2 years ago at 580 yds with my 22" bbl shorty forty custom. I haven't even carried it this year. Muzzle brakes are the cats meow when shooting hot loads in a custom build but I despise hunting with one..
The bottom line is that getting started with a conversion is highly recommended. You get to dip your feet in the water economically before spending thousands on a custom build. The conversion will always be useful. Accessories to get started include a powder scale. This one is both accurate and economical.
https://www.midwayusa.com/ltd/product?pid=840423
If you shoot sabotless, a sizing die will likely be needed. I usually size mine as seen in the below pic. I made a reciever hitch mount for my RCBS Rock Cusher reloading press and the sizing die is threaded in the top where a reloading die would go. A pushrod is installed in the ram in place of a shell holder.
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When considering ignition systems, each has its advantages and disadvantages. 209 ignition is simple, it works, and is cheap. However it does not have the potential of large rifle magnum primers. It is advised to stay away from powders slower than 4198. Wgile it will ignite slower powders, the reliability of ignition is not where id like it to be. Bullet fit must be snug to maintain pressure during and after ignition or it will flame out.
LRMP ignition systems are more efficient, reliable, and capable of igniting slower powders. Depending on powder burn rate and load volume, LRMP ignition will require less powder to get the same velocity as 209 ignition. LRMP uses reloadable modules. However, if you lose your modules, you cant shoot the gun before buying more.
I have a new Henry 45-70 that I'll convert before next season. I'll post my results when it's done. I think I'm gonna hunt with it some this season as a 45-70. Those Barnes 300gr ttsx's for the Sodom are pure death in a 45-70.