Brass trimming for .357 Mag ?


January 19, 2004, 08:42 PM
Is it necessary to trim brass when reloading for .357 Mag ? I'll be using new Starline brass. The dies I’m using are the ReddingTitanium Carbide Pro Series with a Profile Crimp die. I measured about 30 random samples, and most were either 1.281 or 1.282" long, with a couple measuring 1.279 & 1.280. I did find one sample that measure 1.287". These will be fairly hot loads using W296, Hornady 125g XTPs and Nosler 180g partition bullets.

If trimming in necessary, what tool do you use ? I have a Wilson case trimmer and a Giraud trimmer I use for my rifle cases. Thanks.

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Mal H
January 19, 2004, 10:24 PM
Others might do differently, but I don't think I've ever trimmed any handgun brass. They will usually split or become unusable before they would need trimming. Rifle brass is a different matter.

January 19, 2004, 10:44 PM
I rarely trim handgun brass ... BUT!!! I should more often.

I say this because ... with cases from heavy loads in particular .. .357 mag, .44 mag ... I do notice that a crimp is not uniform around a grease groove or cannelure ... the case has very slightly stretched unevenly. I should take a pic but no time right now ...

It does not make a huge difference IMO for most practical purposes but if uniformity and consistency are important to you then i think it is a wise move.

I only use real simple Lee case trimmers ... but at least you do get the mouth back to square again .. instead of as eventually seems to happen .. ''up one side - down the other''!!

If I find a round showing this I'll be back with a pic if I can.


Have looked thru some reloads but can't find a ''bad'' enough example.!! Guess I have pitched some of my real old brass ... which really did show it. Still - if I find one I'll still try a pic later - to prove a point.

Smokey Joe
January 20, 2004, 12:44 AM
With Starline, I'd check the length on several of 'em. If they are all under the max. case length, and all almost the same length (which is what I'd expect from new Starline brass) all the others will be just the same. That being the case, they won't need trimming prior to first loading.

You ought to check the cases' length periodically, say, every 5 reloadings, but with straight-wall pistol cases, as has been pointed out, there is rarely a problem with case stretching. They headspace on the rim around the base, so there is no (or very little) pressure lengthwise on the case as the round is fired.

IMX, Starline is really good stuff as to pistol brass.

Lyman's 48th ed. gives the max case length for .357 mag. as: 1.290". The lengths you quoted, therefore, would not require trimming.

When trimming is necessary, I use a Lee Zip-Trim with a universal case head holder. It's a bit fussy, frankly, but it gets the job done right.

January 20, 2004, 12:46 AM
I have never had to trim a pistol cartridge, however I normally shoot loads that would be considered midrange. If you are shooting pretty hot loads you should definitely keep an eye on the length.

You might consider trimming all of them to the recommended "trim to" length so they will be uniform.

Paul "Fitz" Jones
January 20, 2004, 01:12 AM
I agree with P95 and would trim my brass to identical lengths so my my needed crimp for magnum loads would crimp properly in your bullet grooves at their identical seating and crimping depths.

January 20, 2004, 12:41 PM
I trim revolver brass once, then never again. I do find that the trimmed brass gives a more uniform crimp.

January 20, 2004, 12:52 PM
I trim my 357mag brass at nearly every reloading. One, to make sure they crimp properly, and two, to make sure the COAL using the long Rem SJHP 180s isn't too long for my cylinder when crimped at the cannelure.

I never trim 38special brass. I also get more cracks and splits with 38s than 357s.


January 20, 2004, 12:59 PM
I have to trim .357 brass almost every time I fire it. Some of my worst groups have been attributed to mistrimmed brass of varying lengths. I'm hoping that a FCD crimp die will help solve this.

January 20, 2004, 10:54 PM
Thanks for the replies.

How much of a variance in length do you allow and still get a good crimp ? I’ve been sorting my brass and have them in piles of 1.279 to 1.280, 1.281 to 1.282, 1.283 to 1.284, etc. Most are in the 1.281 to 1.282 range. Would +/- .002 be too loose a tolerance to get a good crimp ?

January 20, 2004, 11:11 PM
For most purposes I'd doubt a thou or two will matter ... if the crimp still pretty much holds on the canelure or grease groove, won't be too much difference.

If hyper critical loads then maybe .. load by case length or ... trim to uniformity.

I think it would be worse if what I alluded to earlier was present ... out of square (uneven) case mouth... then an ''unbalanced'' crimp.

January 23, 2004, 11:22 AM
The case length of the first brass I received from Starline was about 1/2 way between max and trim to length but all was within .003 of each other. I called Starline and their recommendation was to shoot it 'til it reached max then trim it. I've set myself a guideline of .003 since then. As long as they are all within that amount from each other I'm sure of a consistant crimp.

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