I have started shooting in a pistol league and am reloading my forr my 45. Im not real serious about it yet so I'm still using a hodge podge of once fired brass. I'm using the lee carbide dies and the rcbs crimping die to reload with. When mesuring for case length I come up with .890 +/- .003, the books say to trim to .898. My trimmer dosent go that way! Should I just trim to .890 to keep a uniform crimp on all my shells? any help is appreciated looking for anything to tighten up my groups.

I don't know what pistol you use or how it is put together but you might want to start by checking with some "GO" and "NO GO" gauges to make sure your pistol has nominally acceptable head space. You may then want to get some headspace gauges (or borrow them) and measure the headspace in your particular pistol with different length brass. If you've got acceptable headspace with brass trimmed to .890 (measure after sizing) then yes, trim them all to the same length for consistant crimping and bullet tension.

Dillon precision Gase Gage 45acp $9.95

Link

http://dillonprecision.com/template/p.cfm?maj=14&min=0&dyn=1&

The max lenght for a 45ACP is 0.898" and the trim lenght is .0888".
I wouldn`t worry about trimming ACPs, I`ve some brass that`s been fired at least 10 times and hasn`t reached max lenght yet. Matter-of-fact I haven`t ever trimmed a 45 ACP. The stuff acually shortens with the first couple fireings. I would check a few when starting to load a batch and if they aren`t at max don`t worry. You will likely lose them in the grass before they reach max or the mouths will start spliting from working it through belling andcrimping.