To Trim or Not To Trim, That Is The Question.

davef · Nov 15, 2011

Hello,

Regarding 9mm cases: to trim or not to trim? It seems the general consensus online is dont bother trimming. The Lyman book states a 9mm luger trim to length is .751 but ive yet to find a case that even comes close to being that long. It only makes sense that all the cases are the same length so that your taper crimp affects each one identically yet a majority of posts ive read say dont bother trimming. So Im wondering, do you trim 9mm cases? why or why not? If you do trim the cases, what length do you trim to, do you find your shortest cases and trim everything to that size? If you dont, why not? arent you worried that the taper will affect each length differently?

SPU · Nov 15, 2011

I'm not trying to hijack the thread but in the past 24 hours I've been wondering about trimming .357magnum and .38 special brass as well. The advice and opinions are all over the map from "I never trim .45ACP or 9mm but always Rimmed brass, to "I've been loading [insert decades here] and never trim handgun brass. It'll split before you have to worry about it. "

Before I trim 1000+ pieces of brass I'd like to know if it is necessary for general use/plinking versus competiton or SD uses.

And, just to push my luck, Is there any major difference between the major manufacturers of trimmers? I'll need one for rifle brass anyway.

thedude · Nov 16, 2011

"Trimming 9mm"

Never

chrislind2 · Nov 16, 2011

I load 5 different handgun calibers and I always wondered about brass trimming. I have some brass that has been reloaded at least 5 times and I found no reason to trim it. I priced trimmers and put it off because I saw no reason to get one. I will keep measuring and examining the brass and see how it goes, but for now I will save my money.

deadshot2 · Nov 16, 2011

The "Trim, No Trim" question has a fairly simple answer. It totally depends on whether the round needs to be finished with a roll crimp or a taper crimp.

If the round requires a roll crimp, due to either powder requirements (like certain loads in a .357 using W-296) or recoil moving bullets in cylinders or mags, then trimming is recommended in order to provide a uniform crimp. If you don't trim the end crimp will be more or less according to case length, that is unless you adjust the crimp die for every round.

For Auto Loaders most have the case index off the case mouth. Unless your firearm is finicky over headspace the taper crimp does just fine on varying case lengths as it's primary purpose is to just squeeze the brass back against the bullet, removing any "flare" or "belling" that was added to ease seating of the bullet. Excessive taper crimping can lead to the case moving too far into the chamber thus "Headspacing" off the extractor. This can lead to misfires in many instances.

Most cases in autoloader calibers don't grow like the straight walled cases can and they certainly don't grow in length like rifle cases. Trimming of pistol cases, for me, has been limited to only .38 or .357 which both are roll crimped when finished. the rest are shot until they start to split without trimming.

If you do trim pistol cases, the best value trimmer out there is the Lee. A stud and cutter for under $10 with pilot and case holder set a little less. For about $15 one can trim a lot of cases. PS: The Lee Case holder/turner also makes a good polisher. Just chuck it into a drill motor, spin the case, and polish it with a rag wetted with your favorite car wax. Great for finished rounds if you like to show off your finished ammo.

sasquatch · Nov 16, 2011

Overall length of brass is very important, and should be within the specs shown in reloading manuals. Trimming brass is a pain, but may be necessary in certain cases. A good vernier caliper is worth its weight in gold for measuring brass length.

Brass that is too long, as well as too short, can cause numerous problems, some serious. Autoloaders like 9mm, 40 S&W, 45 ACP, to name a few, headspace on the case mouth. That is why a taper crimp is used instead of a roll crimp for autoloaders. For revolvers headspacing is usually not an issue.

Reloading manuals are the best source of info. If you adhere to the specs in the manual (i.e. overall case length), you will be safe. Ignore the specs at your own peril !!

davef · Nov 16, 2011

If you have cases of varying length, like I have discovered, wouldnt the same taper crimp deform a bullet due to too much crimp in one case and be perfectly fine in another case where the case is a bit shorter? Isnt that the argument for trimming cases to the same length or are the few thousands of an inch difference were talking about not going to matter that much.

ma96782 · Nov 16, 2011

I don't trim my 9mm, .45ACP, .38 Special or .357 Mag cases......****, I don't trim my straight walled pistol brass. If I had bottle necked pistol brass (like: .44-40, .357 Sig) I'd have to evaluate that issue.

I figure for most uses.......

Most pistol chambers are generous enough. As for the trimming and the crimp (assuming "enough of a crimp" and a "close enough plus and minus range for length") affecting accuracy.......of course it does but, I doubt that you'll notice when you're mostly shooting a hand held weapon at only up to about 50 yrds. So, if you think about it.......there is the length issue and crimp issue. But, what about the thickness of the brass itself? OK, see how one can over think this?

OK, OK......for me.......
The used brass get's picked up off of the ground and looked at (inspected for splits).
IF you like pretty brass.......clean it. Me, I don't bother with shiney. So, I'll just load them (using a carbide die set).
I've found that this method is so much faster since I tend to shoot alot of pistol ammo.
And.........invest in a progressive press. If you don't already own one.

Aloha, Mark

ma96782 · Nov 16, 2011

SPU,

Trimming RIFLE brass is an issue because, you're dealing with very high pressures vs. pistol pressures.

Check this out to learn more about it:

Internal Ballistics - Hornady Manufacturing, Inc

Yes, there is a great difference in trimmers. Some are geared more towards production and can be expensive.

Example: http://www.giraudtool.com/prod02.htm

Aloha, Mark

civilian75 · Nov 16, 2011

I agree with most of what's been said above. I don't trim handgun brass. Maybe straight walled, and only if I must (uneven mouth, or pushing the limit of a 357Mag load for my 1894 lever action rifle). Handgun pressures are so low and tolerances so wide I do not bother. If any case looks odd, I'd measure it. If it is off, I'd toss it instead of trim it.

Rifle? Yes, because of higher pressures and because every little thing can translate into decreased accuracy.

deadshot2 · Nov 17, 2011

"Trimming" threads should be divided into three categories. One for Autoloading Pistols, One for Revolvers using straight walled cases, and another for all rifle cases.

There are different requirements for each and when one answers "I never trim" it's usually for the Autoloader group which then brings a response "You should always trim" which represents the rifle group. Every one is right when speaking for their own area of interest but not necessarily for the other(s).

chrislind2 · Nov 17, 2011

I measure all my brass before I reload it. At least a large sampling of a hundred rounds, maybe 20-30. None have ever even come close to needing trimmed at least as far as the Speer book says anyway. I keep thinking someday I will measure and have to buy a trimmer, but so far no trimmer. I load 5 handgun calibers two are revolver only rounds. Much of my brass has been reloaded 4-5 times, maybe that is a small number for reloads..?

branchbuster · Nov 22, 2011

I use the Lee trimmer on .357 and .44 cases as well as ALL my rifle ammo.. This makes for a uniform crimp. I chuck the holder in a cordless drill, use the trimmer, then chamfer followed by cleaning with 00 steelwool. With 44 mag I use a very heavy crimp.