I Need Advice

[mike Arnold]

I am loading both 45-90 and 45-70 with Goex 2F & 520 GR. Lyman Postell. I am just begining to approach the case length that will require case trimming. My question is what do you feel is the outer limit on length of when to trim and what length do you trim back to? Do you anneal after you trim?
Thanks in advance for your help.
Mike Arnold

[powderburnerr]

you need to do a chamber cast , to find your chambers exact length and then cut the cases back to as close to the throat as possible . this will help your accuracy in both ctgs. givr them a little for movement but as little as possible.......Dean

[August]

What kind of rifle? Not usually necessary in single shots.

[powderburnerr]

and do you resize every time or shoot fire formed

[Lead pot]

I have chambers that are cut different. Some like the .45-2.1 (45-70) that have a chamber cut 2.1 from the front of the rim and some from the head stamp side of the case.
Do as Powderburner said make a cast that will tell you what you need.
As far as trimming before or after annealing, it dont matter.
Also a case that was fired in your chamber will be shorter before sizing and longer after full length sizing so take that in consideration when you trim or your cases will be too short.
Also a case will get pulled forward when the charge goes off and it will spring back some.
If you trim a case a unsized case to fit the chamber tight it will roll the case mouth like a rolled crimp especially when you shoot black powder.
If you measure from a cast trim the fire formed case .005 less than where the lead starts. Depending how you load, how tight you seat your bullet will depend on how much the case gets pulled, you might have to trim again if you see a slight roll when the round is fired.

[mike Arnold]

To All,
The 45-70 is a Shiloh Sharps 1874 & the 45-90 is a Browning 1885 BPCR Creedmoor. I generaly do not full length size. I have only full length sized when a case has been damaged, stepped on, etc. and needs resized to be repaired. I have not made chamber casts and would like to avoid the hassel.
Thanks,
Mike

[powderburnerr]

then as Kurt says , dont trim them til they start rolling over the edges... that is a simple fix.and cheap..dean

[montana_charlie]

I have not made chamber casts and would like to avoid the hassel.

A chamber cast is not as much 'hassle' as you think it is, and the knowledge gained from it is both valuable and permanent.
The highly useful information you get from a chamber cast is considerably more than just 'chamber depth'.

But, you really should use some method to estimate the actual depth of your chamber.

One way is to...

Use a case intended for the next size longer than your cartridge.
Trim it to a length that is about 0.100" longer than your chamber is thought to be.
Full length resize the case so that it chambers freely.
Expand (or flare) the mouth to .458" (inside diameter).

Slip the case in as far as it will go without 'wedging' it into the step at the end of the chamber.
If it feels 'sticky'...and resists being pulled back out...it is being wedged in.
Expand the mouth a bit more, and try again.

While holding gentle pressure against the case head, mark the case wall with an Exacto knife (or other extremely thin blade) right at the surface of breech end of the barrel.

This resized case is just a depth gauge...not an example of how you should treat your other cases.
Measure from the case mouth to the knife cut.

Trim your ready-to-load cases (resized, fireformed, 'whatever') to this length...or not more than five thousandths shorter if you feel you simply must have some leeway.

CM

[mike Arnold]

Montana Charlie,
I like this plan and thanks to everyone for the good advice. I fell confident that I can get the length sizing done now.
Thanks again.
Your humble servant,
Mike Arnold