HERE IS MY SOURCE (amongst others):
Lyman 49th Edition; Page 362 (40 Smith & Wesson) ; Paragraph 3:
"This cartridge headspaces from the mouth and therefore case trimming must be uniform and accurate. Do not reduce case below the trim-to length. Additionally do not roll crimp bullets as this will prevent the case from properly headspacing on its mouth. A modest taper crimp may be employed if found necessary"
Also, similar info exists on page 380 (paragraph 3) about the .45 ACP
I always trim all my .40S&W brass after the first firing. I did 250 FC cases today. About 170 were < .850", another 50 were < .855" and about 30 were .858" +/- The maximum length is .850" and trim length is .845"...
I will never have to trim these cases again and should get about 20+ reloads out of them.
Melnibonean, you had better check YOUR sources before you go shooting off posts that make you look foolish. Get yourself a good reloading manual and READ IT.
For someone with the amount of words and titles in your sig line, one would assume you would be less.....ahhh......antagonistic? Is that the word I'm looking for?
Let me begin by saying I want to elaborate on my statement. I was referring to the 2 pistol calibers you mentioned as being important to trim and not to all calibers. So in that respect, you are correct and I apologize to anyone who read that if my statement gave the false opinion that I believed NO cases should be trimmed. That's clearly not the case, as illustrated by my trimming the several rifle cartridges I reload for (if they need it)
Next, while yes, trimming straight walled low pressure cases from time to time may be theoretically necessary, you are the 1st who I've read actually does it. I suppose some of my fellow IPSC and IDPA shooters might do it as well, but usually, they don't shoot the same brass often enough to experience the need given the low pressures usually involved.
As p.32, item #8 of the Lyman's 49th edition handbook states (to paraphrase)...trimming may not always be necessary. Maybe the Federal brass you referenced - being amongst the softest brass - stretched by the amount you claim owing to this quality of Federal? Because, as the Nosler 2012 reloading manual states on p.55 "In general, high velocity, tapered, bottleneck cartridges will stretch out their cases faster than low pressure, straight walled cartridges." As you know, most pistol brass fall into this category. Anecdotally, I've been using the same batch of .45ACP brass now for going on 5 years. Still works perfectly fine in all my pistols chambered in .45. I lose them rather than have to trim or replace them. The only problem I have had with .40s was the "glock bulge", and another time with my 9mm loads, which were traced back to a re-sizing die that had backed out and wasn't sizing properly; not a cartridge length issue.
I wonder why you trim to .845". Speer's reloading manual #14 says to trim to .840", although my Lyman, Hornady and Nosler manuals say .845". Would seem to me that given the longevity of .40 brass isn't so great to begin with, I suppose you could trim to the Speer length and then by the time you shot that brass enough to stretch it out to .850" (if ever), it would be time to toss it or it would be lost. Then again, I've always found COAL to be important - despite seating to fit in the specific magazine - due to pressures being more of a concern (if the bullet is seated too deeply) in pistols using faster burning pistol powders. Would you agree?
But it's your time and your gun and if you want to trim every individual pistol brass by hand, more power to you. For the amount of pistol shooting and reloading I do (and given that Dillon doesn't make a die for the rapid trimmer in pistol calibers), I choose not to. Most shooters don't either, BTW.
Thanks for letting me clear that up.
