Help with case trimming for 40 S&W

[ZLBubba]

I just got my Forster original case trimmer kit in the mail yesterday. The manuals say that the 40 S&W case needs to be trimmed to .840, but the Sierra reloading manual diagram says that the case can measure up to .850. Most of the cases are between .845-.847 after being fired.

I didn't get a .40cal pilot with the case trimming set so I will obviously have to order it. Nonetheless, will I be safe to load box of rounds since the case length is still below the max length? It seems like the rounds should be fine, but I wanted to ask here to be sure.

 

[DustyJacket]

Re: Help with case trimming for 40 S&W

Yes.

When my cases got to the max, I would trim them down nearly to the minimum, and not trim again until they hit the max.

But that is just how I did it.

The more consistent way is to chose a length that works for you and trim to that length every time you reload a case.

 

[ChadTRG42]

Re: Help with case trimming for 40 S&W

As long as they are under max length, you are fine. But why would you want to trim a 40 case. Just throw it out and go to the next case. They are very inexpensive and IMO, are not worth the effort to trim, chamfer and debur. I never measure my personal 40 ammo brass length, and I buy all once fired cases to shoot.

 

[sawgunner2001]

Re: Help with case trimming for 40 S&W

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">As long as they are under max length, you are fine. But why would you want to trim a 40 case. Just throw it out and go to the next case. They are very inexpensive and IMO, are not worth the effort to trim, chamfer and debur. I never measure my personal 40 ammo brass length, and I buy all once fired cases to shoot.</div></div>

I agree with everything said here.

 

[918v]

Re: Help with case trimming for 40 S&W

Trimming cases to the same length promotes a more consistent taper crimp. Also, because my Lyman flash hole uniformer indexes off the case mouth, trimming promotes a consistent flash hole funnel diameter. No, my pistol won't do any better than 12 MOA, even with all this case prep

 

[jdgray]

Re: Help with case trimming for 40 S&W

I never trim pistol brass, and it usually gets shorter.
Now 357 mag brass will stretch, and for roll crimping, you want them all the same length.

My 9,40,&45 brass never gets trimmed.

 

[ChadTRG42]

Re: Help with case trimming for 40 S&W

You shouldn't taper crimp a 40 case, or any handgun case that headspaces off the rim. I seriously doubt you could see any difference in accuracy or in SD or ES numbers from the chrono if you fired trimmed brass to minimum or brass that was at max length. I know I could never see a benefit from it in accuracy. And did I mention I HATE case prep!

 

[918v]

Re: Help with case trimming for 40 S&W

You should taper crimp slightly, but not dig into the bullet.

 

[ZLBubba]

Re: Help with case trimming for 40 S&W

This is great information. I was ready to order another pilot but if it's not worth the effort, then I'll just keep trucking. I'm just beginning the whole reloading process so I'm being as careful and as precise as possible until I get more comfortable. I see the point with pistol brass being as cheap as it is. The effort to trim probably isn't worth it.

 

[Queequeg]

Re: Help with case trimming for 40 S&W

I've never trimmed pistol brass. Revolver brass, especially for hard kicking cartridges requiring roll crimps in cannelures, should get them but I haven't had to trim my .45 Colt or .38/.357 brass yet.

I have two Forster trimmers, one was a gift and the other I bought because I liked the first so much. I leave the first set up for .308 and use the other and my older Lyman for other cases. With Forster you'll need the correct collet as well as the appropriate pilot/mandrell.

I'd watch your case lengths over numbers of times fired/reloaded and look for any growth beyond tolerances by checking samples as you go. You'll likely find it unnecessary as well.

 

[user]

Re: Help with case trimming for 40 S&W

Never heard of trimming a .40 SW....wow, lots of work...just buy more.