I am having a trim to length quandry. I have two books, Hornady 8th edition and Lyman 39th edition. The problem I am having is my cases are short. The caliber is .380. The cases are new and once fired. The two books call for .675-.677 CTL. The new cases are Winchester and measure between .670-.674! The once fired are .672-.675 after resizing. How am I to set bullet depth? Do i cut them all to a reasonable static shorter length and not worry about what the books say?
Last edited by 10mm Witness; 07-08-2015 at 06:30 PM. Reason: Typo
Trim to shortest length to just square up the fired cases then the new cases this makes for cases that will crimp fairly consistently and after a few loading firing cycle will probably need triming again. On most rounds actual measured case length isnt as critical as uniformity, But with rimless pistol rounds that headspace on the case mouth you want to be fairly close.
The length in the book is MAX length for your cases as long as they are that length or a little shorter is fine.
CD
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If you're loading for .380 I really wouldn't worry about trimming the cases
Like Jrap said, don't worry about trimming handgun cases (normally).
If the cases are a bit short, simply seat the bullets to the proper over all length. The internal volume of the case is unchanged - unaffected by the length of the case past the base of the bullet. As long as the OAL is correct, the cartridges will not bounce back and forth in the magazine, will fit IN the magazine and will function through the action.
Crimping is the only process that might be affected. However, straight sided semi-automatic pistol ammunition is normally taper crimped (if at all) and not roll crimped. So the non-standard lengths are not going to be a problem there either.
If such cases are too long, the case mouth could be jammed into the end of the chamber and cause a very tight grip on the bullet. This could raise pressures above acceptable. Too short is not a problem, unless one cannot properly seat the bullet.
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By the measurement given I would trim everything to .670 if possible. That way the crimp will be consistent.
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I've been shooting straight wall pistol for around 55 yrs & have never trimmed one. You'll probably loose it before it needs trimmed.
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