How much do you expand a .45-70 case mouth for cast bullets?

I am new to cast bullets! When loading .45-70 cases with cast lead bullets, some of the bullets coated and others instead conventionally lubed, how much should I be expanding the case mouth to avoid shaving the lead bullet?

My measured average bullet diameter on the first type of bullet being loaded, the Missouri 405g cast bullet with "Hi-Tek" coating = .4588"

My SIZED case OD on brand new cases = .468"

My Winchester case wall thickness = .0110

So, 2 x wall thickness = .0220"

Doing the math, for a "slip" fit with ZERO clearance and NO tension, the case OD would be
= .4588 + .0220 = .4808"

So, what case OD should I be targeting to have the "right" amount of belling for inserting the bullet and seating without shaving the lead?

I will be using a Lee Factory Crimp die.

The ammunition will be used ONLY in a single shot Pedersoli Sharps.

Jim G

The shaving, if it occurs, will start and be obvious before you go far enough to destroy the bullet and necessitate disassembly of the primed and powdered cartridge? Or do you discover it once the bullet comes out of the seating die along wth some slivers of lead?

Also, can you get a situation where the bullet seats but the COATING on it gets scraped?

Jim G

Obturation said:

Don't over think this , just big enough is perfect. If you're shaving a little ring then put the expanded down some. You don't need to be ultra precise . I stopped using the lee expander , I find the rcbs. (M die??) Expander does a more even /less cone shaped expansion. Cast lead likes that .

Click to expand...

I forgot to mention I am using the Hornady 3-die Custom set for 45-70. It has some really nice features including a sliding tube in the seating die that encloses the case and bullet and slides up as the die slides over it. Plus, I ordered the Hornady "Microjust" which enables micrometer adjustment of the seating height. That is important to me because I will be using multiple different bullets requiring different VERY different COALs.

Jim G

mdi said:

Flare/expand as much as needed to be able to start the bullets easily, straight. If concerned about too much neck tension, seat a few bullets, then pull using an impact puller and measure the bullet diameter for swaging.

Click to expand...

Actually, I am going to use the Lee Factory Crimp die for getting consistent tension on each cartridge. So, to prevent any bullet shaving or scraping of the Hi-Tek coating, I should, if anything, go for sure with a large enough expansion to ensure no shaving or scraping?

Jim G

Should I also be chamfering the inside of of the case mouth when using brand new cases, and also later when the cases have been through a trimming?

Or, is that unnecessary when loading for a single shot rifle, expanding just enough, and using a Lee Factory Crimp die?

Jim G

Ok, the specific type of bullet I am expanding for today has a chamfer on its base. That is obviously a smaller diameter than the shank of the bullet. I assume you guys mean that I have to be able to get the SHANK above the chamfer started into the case "about a dime/nickel's width" (MEHavey probably meant "thickness of a dime or nickel, not width!)

Jim G

Ok, here is what did today:

I chamfered the case ID, not the D, and I did it very lightly - just making sure there are no burrs basically.

I set the expander die up and starting slowly, incrementally increasing the expansion of the case mouth. The 405g bullets I am loading have a chamfered base - maybe .06" high. I went deeper with the expander by maybe less than .06" more, so that I was catching the unchamfered shank of the bullet, and the bullet would stand up reliably in the case without falling off. I noticed that once I hit a certain point in expander depth - far below the .10" to 12." TOTAL expander depth - the expander no longer increased the diameter of the case iD.but rather simply went deeper into the case at the same ID, which was a thou or 2 less than the .4587" average bullet shank diameter. So, evidently, Hornady ENSURE that you do not over-expand on diameter.

Also, the expander left a clearly visible "band" on the case ID, from mouth of the case to the maximum expander depth, so I could easily visibly confirm after expanding each case that no individual case was noticeably different length than any others.

I made one complete case & bullet assembly (no primer and no powder), set up the Hornady seating die, and incrementally seated the bullet deeper and deeper, until I got to 2.550" COAL. But, at that COAL, the mouth of the case was a little lower than at the crimping groove on the bullet. I found that if i seated it just a few thousandths deeper (about .008"), the case mouth aligned with the crimping groove. Given I will be running CAS level loads (1200 to 1400 fps range) at 14,500 to 16,000 pressure levels), not high power loads, I figure the .008" thousandths shorter COAL is not a pressure raising problem.

I made sure I had the seating die set to near the bottom of its micrometer range for the 405g bullet, because the other weight of bullets I want to try is 500g, and those bullets will be MUCH longer (one of the 500g samples my buddy gave me has a "pointed" tip and is about .40" longer than the 405g bullet!

Then, I disassembled the dummy cartridge using an inertia hammer, and checked the condition of the bullet shank. Found NO shaving or scratching of the Hi-Tek coating. Also found that the shank diameter was unchanged: the bullet started at the batch average shank diameter somewhere between .4585" and .4590", and stayed there through the seating process and the inertia hammer removal process.

So, I THINK my setup is good to go. Just need to settle on a powder range for both Accurate 5744 and IMR 4198 for the ladder testing, and also set up the Lee Factory crimp die for a modest crimp.

Did I miss anything or do anything wrong?

Jim G