Shiloh Rifle Forums

Yesterday, I posed a question on the method to cut 45-90 cases to fit my 45-70 rifle. Several responses were received, to which I have chosen a method. My question today is what length would be best to first trim to. My chamber measures 2.114 inches and I plan to mostly shoot paper patched loads. What effect will fireforming and resizing have on the cartridge OAL. My experience with pp loads is to have the case dimension best matched to the chamber length. Most of my Starline cases have never been loaded, but some have been shot and resized in the 45-90.

Fl sizing makes the cases grow more than anything. How are you sizing to hold the bullet?

Light taper crimp.

Light taper crimp.

I'd trim a few cases (5-10) load and shoot them until you get a good idea of exact length.

Trim them to just fit, load without any neck tension, shoot them and measure them again.

Bryan

ideal case length for black powder cartridges is a complex thing.
firstly it depends on the task in hand.
hunting ammunition can be better with neck tension as function in that environment is a priority.
talking target ammunition is a different thing altogether.
the first thing we must remember is that a sized case is longer than a fired one.
the minute the primer goes bang, the case gets shorter.
we do not want the case mouth to go into the chamber transition, as it forces a crimp into the bullet.
we do not wand a gap between the case mouth and the transition, as the bullet will bump into it causing potential leading, lead rings, and/or paper rings.
best case scenario if this happens is a reduction in accuracy.
the best way to minimize these things is to have the case mouth a few thousanths short of the transition before firing, during firing, and after firing.
the best way to achieve this is to use correctly tempered brass that is fully fireformed at the correct length described above, and finger seat bullets with just a little friction as the bullet slides in.
get a crap cheap mould and fireform the brass enough times that it is stable to the point where it springs back 0.001" on firing, then you can get a mould that makes a bullet to fit the cases perfectly.
the bonus of this is that a bullets sized that way will be potentially the most accurate.
bore diameter pp bullet fit you ask?
this is where you either have a correct chamber for the job, or use dual diameter bullets if your chamber is for groove diameter bullets.
bruce.

bruce m wrote: ↑Mon Jan 11, 2021 5:14 pm
the best way to minimize these things is to have the case mouth a few thousanths short of the transition before firing, during firing, and after firing.

I think it was Coltsmoke that said something about overlong cases last year that caught my attention given the accuracy of his loads during last years frostbite. Unfortunately i can't find it so i cant repeat it.
Maybe he will chime in.

try the DDPP bullets, and never re-size. unless you have to. may be a little more expensive as you will have to buy another mold but, not having to re-size is one less step and I feel you can better control your taper crimp better,

matt

sorry on the length, I trim mine .003-.004 short of chamber length. Found that by doing a chamber cast.

if you are sizing brass, you have 2 case lengths, sized and unsized.
finger seating correct sized bullets in fireformed cases, you are using the correct size case length.
in fact this is the only way to be sure..
problem is with this is that some guys are simply too tightarsed to get the right sized mould, or unable to see or distinguish any advantage.
who knows, a crap mould might even be the right size, but by the time you have bought a number of them it would have been cheaper to just buy a good one made to spec..
bruce.

Above......times 2