Hi,
New to the forums and am getting my feet wet with reloading. I'm starting of w/ .40 S&W & 10MM.
Got the reloader set up, deprimed and resized the .40 casings. When I take the measurements, most of the cases are shorter than the "trim to" length recommmended in the reloading manuals. I'm not trimming these, I assumed that is the minimum case length. I contacted Dillon who told me cases will continue to get short after each use. Okay. If that's the case (no pun intended), what is the minimum case length and exactly what am I measuring for? Is there a min and max by percentage for different cases?Thanks for your help.
48M

Thumb rule is that Trim-to is .010 longer than Minimum and .010 shorter than Maximim. The one case I can think of that dosn't follow this rule has the Trim-to equil to the Minimum, and the Maximum is .020 longer than both.

With Pistol brass, they get shorter/fatter when fired and longer/skinnier when sized. The pressures are also not high enough to cause the brass to flow forward (rifle cases are another story)

quote:

Originally posted by 48 Months:
I contacted Dillon who told me cases will continue to get short after each use.

I dearly love all my Dillon equipment but I think that answer is just so much BS. If it were true, the 9mm brass that I've loaded time after time, after time, would shrink to no more than a nub. Funny, they have not, and they headspace just fine to this day. Same goes for the 45ACP brass that I've been reloading for decades using Bullseye powder and homecast lead boolits.

A consistant case length is not of a high priority when a taper crimp is used,i.e. .40 S&W or 10mm Auto. They do however need to be shorter than max case length to chamber. Only if some rummy has trimmed them below min. would there ever be a problem as the ,40 and 10mm index on the case mouth. Not a dangeruos situation by any means as they would just not fire.

Using a roll crimp is an entirely different story as these rounds index on the head of the case, i.e. .44 Rem Mag or .357 Mag. To get a consistant roll crimp all cases must be trimmed to a consistant length under max.

One other thing when taper crimping .40 or 10mm, set your crimper/seater die so the case mouth gets swaged/crimped .002< than the bottom of the case body. This makes it smoother and will not hang up when chambering. I learned the hard way!
Hope this helps.

As far as what Dillon told you, you must have misunderstood what he was trying to tell you. In my limited experience all cases will lengthen , straight walled pistol or bottleneck rifle, the more times you fire them. It is true the increase in length will slow down the more you fire the case as long as you only neck size. If full length resizing, the case will get longer with each subsequent sizing till you need to trim again. The brass you trim off used to be in the case wall/neck and will thin the case resulting in case head seperation or split necks. Keep in mind a split neck is also an indication of overload or hardening of the brass from repeated full lenghth resizing.

Fishin' Magician

Check your brass in the resized condition.
They will get longer again.

[QUOTE Is there a min and max by percentage for different cases?
[/QUOTE]Pistol brass that headspaces on the case mouth should not be trimmed more than .003" and only if they grow over the maximum length allowed. A min & max is listed in reloading manuals. 45acp types may never need trimming as they headspace on the case mouth. Bottle necks like 243, 30-06 will need trimmed back .010" from max , these headspace on the shoulder of the brass. Check any brass after FLRSing. If you look at these drawings, you will see the MAXIMUM measurement for a cartridge.Never let your brass get longer than what is shown in the drawings. http://www.stevespages.com/page8d.htm Here is another article on trimming. http://findarticles.com/p/arti...is_1_48/ai_80635898/

Thank you everybody. I'm on to the next step.