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

[Chief TC]

I keep it pretty simple like others have mentioned. Use an expanding die and and adjust until it flares it enough for you to start the cast bullet. Don't crimp for single shot rifles but sometimes using the crimping part of the die will close the flare properly. If you are only using smokeless load then FL size after each firing and flare only enough to accept bullet. If using BP, once they are fire formed you can just seat the bullet without an expanding die. I find BP more accurate than smokeless but you employ fouling control with BP which keeps the bore prepared.

 

[Chief TC]

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

Seems like you got it generally figured. At those velocities, you can have the bullet touching the lands with no worry in increased pressure. 5744 is go to powder. My 520gr cast bullets do well with it. Accuracy is better with no crimp, so just flatten out the flare.

 

[JimGnitecki]

Seems like you got it generally figured. At those velocities, you can have the bullet touching the lands with no worry in increased pressure. 5744 is go to powder. My 520gr cast bullets do well with it. Accuracy is better with no crimp, so just flatten out the flare.

Thanks, Chief TC. I have been getting a range of advice on crimps, but my go-to successful so-far crimp solution, across a wide variety of handload in different calibers and tpes of shooting, is basically what you said: just flatten the flare and sometimes a very slight .001" or .002" "squeeze" just for consistency.

 

[johnjohn]

Some great words of wisdom here. But as some have said" keep it simple" don't "over think " this keep it simple.