My trusty old RCBS rotary case trimmer doesn't have a collet for 375 Flanged, 450/400 and other cases with large rims. Rcbs doesn't make collets for theses cases. So if I'm going to have to buy a machine to trim big stuff, I'd like to hear some recommendations with justification.

I have ordered several custom case trimmer parts for the Lee trimming tool. It is not adjustable or very fast to use, but is really uniform. The uniform length makes crimping uniform. Don't know if it will work for what you want. I kept having fliers with my .45-70 until I tried the Lee trimming tool and got a more uniform crimp. Lee made pilots for me for the .458 Lott and 9.3x74R.

I bought a Forester case trimmer just for 450/400 and 450 NE brass. Works great but these trimmers can be hard to find sometimes.

Wilson beats every single other make we have tried.

Make a threaded tool to join a collet to a case holder, and a mandrel for the neck, then a South Bend Heavy 10 spins the works.

I don't see any Wilson case holders for any of the tropical/NE cartridges. Sure looks like a nice trimmer, though. I hate my Hornady.

I use a 12 inch engine lathe.

I'm thinking that little crow gun works' worlds finest trimmer big boy is the ticket. Chuck it in a lathe or mill or drill press, hold the case by hand and you're done. All of the adjustment is in the trimmer and the cutter is simply a milling cutter. https://www.littlecrowgunworks...-Assembly-p106089998

I prefer a file trim die, they are more accurate than anything else I assume..a lathe?? I don't know but I would suspect it would be very accurate??

Or the Lee type; like a file die, you can't possibly make an error.

VOL717, sending you a PM that may prove helpful.

I particularly like a file trim die as its accurate and your crimp is the same on each case. run the case in the file trim die and file off what sticks out the top, how fundamental can you get. It works an cost about $20 bucks last I bought..

Also most double rifle cases are soft and thin and prone to crushing, You can go by feel with a file..

check out Little Crow gun works and their WFT (Worlds finest trimmer) I have 3 of them and they work great.
https://www.littlecrowgunworks.com/

I also like the taper crimp die to go with a file trim die or any die for that matter..Lee, RCBS, whatever, they all work. Especially on big bore double rifle and lever action cartridges..and pistols..