March 13, 2025

The 45-70 and neck sizing

This topic can be controversial. The important thing is to think about it, evaluate what gun you have, or if you have more than one gun, and what you do with it.

It makes great sense to me, and I have begun doing it. I have only one rifle -- if you have more than one, this may not work for you.

First of all, my rifle fired these rounds -- and ejected them! So it is only reasonable that they will go back into the same chamber they were ejected from, in fact they are nicely fire formed.

All we need to do is to squeeze down the neck area so it will grip a bullet again, and we are in business.

What I just did

I am using a Lee full length die. I just turned it up 4 full turns from the "contact the shell plate" position I previously had it set to. I measured the inside neck diameter at 0.450 after doing this, which is more than adequate to grip a 0.458 bullet. In fact I could probably go another turn or two.

Some people say they do as much as 7 turns, but I like how things feel with only 4. I'll use it like this and perhaps reevaluate after getting some experience with it.

I an using a dies with standard 7/8-14 threads, so this has moved the sizing die up by 4/14 of an inch -- 0.286 inches. As you probably know, the 45-70 case is gently tapered. I notice a considerable reduction in the amount of force I need to use to resize cases, and I can now use a lot less case lub (I am using Imperial die wax). So it seems like a total win to me. Here is a video:

Lyman neck sizer die

Out of stock everywhere right now, and I am not clear if it offers any advantage over what I am doing just backing out my full size die. They make it in long and short versions. They say you want the short version.

Redding also makes a neck sizing die.

An even better way

Lee makes a die they call the "45/70 Collet Necksizer". The idea is that it compresses the neck of the case against a precision mandrel inside the case. This makes the sizing independent of case wall thickness and improves concentricity.

The really big win is that no lube is required!!

The big downside is that this die is manufactured to work with their "breech lock" system and will not work in a standard press. Their breech lock has 1-1/4-12 threads, not 7/8-14. Some presses can be modified to use their breech lock dies, but not my Forster Co-Ax. So, as much as I would like to use this system, I would have to buy a Lee press to do so.

I could curse them for not making this in the standard 7/8-14 -- and I have. However it is possible that they just need the extra diameter to accomodate the mechanism. The next time I see Lee gear on sale I will see just what one of their basic presses would cost me.

If you do buy a compatible press and get into their system, you can buy "quick change bushings" to adapt standard 7/8-14 dies. The least expensive compatible press I have found sells for about $70, so along with $30 for the dies, you would have to pay $100 for the convenience of using the collet neck die.

Midsouth was having a sale on Lee gear, so I bought this thing and spent about $60 for the cheapest of their presses to go with it. It all arrived. The press itself has a lot of friction. I oiled it, and hope it will break in. If it doesn't, I will remove the ram and work on it a bit with 600 or 1000 wet/dry paper.

A surprising issue is that the mandrel and primer knockout pin are one piece! I want to resize about 400 pieces of primed brass! I ordered another mandrel from Lee (for only $6 plus $7 shipping) and plan to just cut the primer pin off the mandrel I have. It is doubtful I will ever deprime fired brass on this anyway -- I will deprime them with a universal decapper die, then tumble them clean.

I suppose I could bypass even tumbling and just use this to neck size and deprime, then load up again. The shortcuts seem to keep offering themselves with 45-70.

Feedback? Questions? Drop me a line!

Tom's Computer Info / tom@mmto.org