The groove in mine, is also .410. I bought the Lymans Snover designed 410663 mold for it. Because the twist in the 40/63, is 20, I shortened it to 1.29 long (about .050 as I remember) and opened the base band .002.
I bought a tapered Ron Long mold so, I don't use it any more and it's for sale.

Frank

I use two RCBS CSA molds that drop a 300 and 350 gr. bullet. The 40-300-CSA and 40-350CSA molds have both shot well in my Pacific and Rigby Ballards in .40 caliber. Both have the old slow twist, but the Pacific is a .40-85 Everlasting, and the Rigby is in .40-63 everlasting.
I have the heavier Lyman .410" molds in 410665 and 410663 also, but the recoil isn't as pleasant as the two RCBS bullets. They all shoot well, even out to long distances, I just prefer the lighter recoil of the light bullets.

Back in the 70's I bought some 40-70's for a Ballard and the like from James J Grant. So I got only a limited few but now I had all the measurements I needed to make some out of new stuff.
1. get 30-06 brass
2. turn the head down so I can put a rim on it. I used a brass washer
3 press washer on it and solder. 
4 trim washer to correct rim diameter and thickness
5 fire form the brass.
6 trim to length

Now you have cartridges to shoot and high strength brass
a lot of work but in those days brass was not available like it is today, and we didn't have the internet for assistance
I think I still have some of those laying around

                         Once upon a time
                                    Don

Hunts on Mule wrote on Mar 21^st, 2018 at 8:41pm:


I use the K&M neck turning tool. I have tried both outside and inside neck turning, and prefer outside as it wont leave a ridge that affects bullet seating depth. 
But I have some cases for my .40-70 that a friend inside turned and he couldn't use them for his heavy 400 gr. bullets, but they work great for my lighter bullets.

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