I've just purchased a previously owned Shiloh #3 in 40-70 SS.
I would like to know the correct maximum case length, and correct trim to.
and also the maximum neck diameter with bullet seated. My groove is .408, but using .409 25:1 alloy bullets, I'm having trouble chambering rounds. I'm using RP brass from Buffalo Arms.
I'm wondering if I need to turn the necks a little more. Even with a tight chamber I'm sure there must some room available to release the bullet properly.
You could very well have the older chamber size which was 0.430" whereas the new measurement is 0.432". Doesn't sound like much, but do the math and you see that you don't have a lot of wiggle room. My solution was to run the loaded round through the sizer die (be very carefull with this maneuver - taper crimp die does not work) until the OD of the neck was 0.425" to 0.427". This ensured that the loaded round would chamber under hunting conditions and gave 4" groups at 200 yards off a bench. Not match accuracy, but worked great on the critters I ventilated with that process.
The chamber could be opened up to the new 0.432" dimension, but if you are not going to get real serious about match shooting, I wouldn't mess with it. Trim brass length to 2.498" to 2.499". Chambers in the Shilohs that I have worked with are right on the money for size. In a hunting situation you will want to seat the slug to the top of the last groove to avoid contamination of the lube portion of the slug. The match shooters go a different route and expect different results. You will need to determine which route you wish to travel and go from there. The 40-70 SS is a great little cartridge and you will enjoy it.
Canyons,
Instead of neck reaming why don't you try a .407" or smaller diameter bullet instead. In my 40-70ss i went through the same problem. As soon as I went to the smaller diameter bullet all my troubles w/ this rifle went away. My accuracy improved and the chrony readings w/ swiss powder were excellent. I used to believe that the lead bullets needed to be groove diameter or bigger. Now - all my target BP loads use groove diameter or smaller bullets. Worth a try anyway....who knows!
Hi Sir, If you are not happy with any of theses ideas, and they are good ones, go ahead and send the rifle back and I will punch the bigger reamer into it, which will be .432". Thanks Kirk
My thanks to everyone, I will try the techniques listed. It's great to learn of other tried and tested methods. I would rather leave the chamber as original, but glad to know there are options. Checking neck thickness I do have some variation resulting in greater than .010" neck wall thickness on some brass in some spots, so I will true the necks to .010" first, which is thinnest I've measured. I did have to trim some brass that was over 2.500 and have taken care of that, trimming back to 2.498 which was the shortest measured. I still have some brass (New R-P) that even full length sized, trimmed, chamfered, and empty requires the lever to be bumped with the palm of my hand to extract, they won't quite just slide out of the chamber. That I'm thinking is a brass or die issue, as smoked cases show interference either on the neck or just about even with top of shell holder.I may have to take a .001 off top of shell holder and see if that cures those particular cases. I'm using RCBS dies and they may be just a little big for this particular chamber. So with the ideas listed and making adjustments with brass, dies and bullets it's going to be great. Thanks again to all.
