Trimming Brass

N

ninosdemente

New member
I was online looking for RCBS shell holder chart and found a couple pdfs and some online ones. I found this one in particular that had the max length and the trim length.

https://op1.0ps.us/pdf/opplanet-rcbs-trim-shell-holder-ref-chart-pdf.pdf

Now I initially compared the calibers of interest to me to the Lyman 50th (30-06, .223, 9mm, and .380). Out of those 4, 30-06 and .223 had the same trim length in the pdf and book. For 9mm luger the case length are both at .754 where online trim length is .744 and in the book trim length is .751. The .380 both have same case length but the online trim length is .670 where the book trim length is .677.

Now the pdf does not indicate source of information for verification if possible so this only makes me think to only follow what the book says.

Is going below trim length from book a good/safe thing to do? Is there an acceptable tolerance of how much can be removed from what the book indicates?
 
Is going below trim length from book a good/safe thing to do? Is there an acceptable tolerance of how much can be removed from what the book indicates?
Click to expand...

Trimming below recommended length is fine when trimming for cartridges that headspace off the shoulder , rim or belt like 30-06/223 , 30-30 , 38/357 or 300win mag etc . There is a point where you can trim to much resulting in to little of bullet hold because not enough of the neck is gripping the bullet anymore . Generally speaking though if you go a tad shorter then recommended length you should not have a problem .

You do not want to trim below suggested trim length on cartridges that headspace off the case mouth like 9mm , 380 , 45acp , 40 S&W etc . When head spacing off the mouth of the case , It's the case length it self that determines the proper fit in the chamber .


I'll look up what SAAMI says about the 380 EDIT : SAAMI minimum trim length for the 380 auto is .670

9mm - SAAMI minimum is .744 and max is .754

223 Rem - SAAMI minimum is 1.730 and max is 1.760 . I trim mine to 1.750

30-06 - SAAMI minimum 2.474 , max 2.494 . Seems splitting the difference is the norm so trim to 2.484
 
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Nino,
For the most part i use Lee case length gauges. Has a post set to length.

For pistol cases380, 9mm, 45ACP i do not trim. Frankly not worth the time, as there is no shoulder for the pressure to push upon.
 
You're wasting your time if you're looking to trim handgun brass. They are for the most part too short, not too long.

Don
 
I haven't done any trimming of handgun brass. Being a beginner and seeing trim length on the book only naturally made me think that I did. Good thing I asked first. Thanks.
 
Thanks for asking. Still new myself and trying to learn all that I can while I go. I read lots of posts that likely don’t apply to me, just to absorb any new tricks or tips that I may need later. I bought a nice case trimmer, but looks like I’ll just be mounting brushes and primer pocket cleaners...and there’s nothing wrong with that!
 
While i do use the Lee case length gauges, old school on my rifle brass, i've been eyeballing the Lee Quick Trim. Trims, camfers and deburrs in one step. Issue is the need for a "trim die" ($5) for each different cartridge. Aka 250Savage, 257 Roberts etc..
 
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