Acceptable Case length variations when trimming (.357 mag brass)

Your acceptable tolerance in trimming depends on the tolerance you will accept in your crimping.

With the batch you trimmed, I'd agree they should be fine. But I would keep trying to see if you can get them all to 1.280" on the next trimming. The Hornady Cam lock trimmer works great. Team those cases with a Redding Profile Crimp die for really nice uniform crimps.

if I am going to go through the effort of sizing them all, is this close enough?

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Well, there's your problem rat cheer there!!!

You must always resize brass before trimming it!

Always, no exceptions, Always.

You don't know what length it will be, before or after trimming, until after it has been re-sized first.

rc

The size of the crimp groove on cast bullets is not always the same. The one on the left will be ok with .005" difference in case length. Less on the right one.

Yes...trim them. 2 thousandths is negligible...

For wheel gun brass the only two things that really matter are cylinder fit, and having enough roll crimp to do it's job.

As to fit, if your brass gets too long, it can cause excessive OAL, which in some wheel guns can cause problems with the bullet protruding from the front of the cylinder, thus interfering with cylinder rotation. Other wise, there is no issue in this respect.

Regarding crimp, trimming to within +/- a couple thousandths (.002") will be close enough to keep crimps consistent.

But there is no reason to not use the short one's, unless they are excessively short for .357 mag. purposes. If your .357 mag. loads are full tilt 296/H110 loads, or the like, a good roll crimp is absolutely necessary to prevent bullets from jumping the crimp. So when ever I run into this situation, I just adjust my die down far enough to do the job, then proceed by crimping the short one's by feel, being careful not to crush any.

But if they are really, really short, you can trim/cut them down to 38 spcl, length, and then use them for those loads, if so desired.

GS

Guess I am the odd man here. I have reloaded the 357 for 30 years and have yet to trim a single case.

jmorris said:

Guess I am the odd man here. I have reloaded the 357 for 30 years and have yet to trim a single case.

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We are both odd then.

Well there is certainly no concern in not trimming wheel gun brass, but there is the practical aspect of consistent roll crimps. But if the loads are in the target pressure range, little to no crimp is even necessary. But most certainly full pressure loads need a good roll crimp to both, prevent crimp jump, and to produce a good consistent powder burn.

GS

What I do:

When I first buy NEW or USED pistol brass I always size and trim them to all the same length.
Then after that I never trim.

Revolvers are forgiving on length, but I try to keep them all the same.

That's Just Me.

TxD

I have upwards of .01 delta in the size of my brass pieces, too long I do trim. I usually take the tallest piece from a brass I'm going to make (or close to it) and crimp at the very top of the groove with it. If any go too low (which very seldom happens) in the crimp goove, I'll but them aside, and seat them a tench deeper. I have yet to trim any .357, brass. I do trim all my .38 brass 1.15 or longer to 1.148. Most of my .357 brass is in the 1.274 to 1.284 range.

I trimmed a few handgun cases somewhere around 1970-1971. Then I stopped and have yet to have a problem. Maybe I'm just lucky.

My goal on this matter is getting a uniform crimp.

To me that means setting the crimp die and locking it down and using the same case length.

Making adjustments to the die within a batch is simply not uniform to me.

Whether the cases are trimmed to 1.280" or 1.281" or 1.290" or anywhere in between is fine as long as they are all the same length. Any shorter, just adjust the powder charge considering a 38 special load and the COL will be controlled by the cylinder.

I keep 357 brass at 1.280" and do not adjust my 357 crimp die, ever.

1.283" is different than 1.289". Granted, its not much and we can't see it, but we measure dimensions to the thousandths easily and often.

In practice, I don't measure 357 cases. They just all go through the trimmer - set with a "standard" case, after resizing. I can trim, debur and chamfer as fast as I can measure and do any kind of sorting or adjusting of the dies.

Does it matter, I don't know. I've always trimmed 357 cases. I read it in a manual at the start and my crimp die says to trim cases for uniform crimps. With all the voodoo science of internal ballistics that we can't control - this one thing can easily be controlled.

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What HE said...Amen...

I've never trimmed handgun brass. BUT, I have measured some on occasion and found a +/- variance of ~.002 and they've always shot fine.

I do agree that if you wish them to be perfect, and are looking for the perfect crimp. Trim them and crimp them, and be happy

BUT, will that .002 excess harm your pistol? Nope, not at all

Mike B