7mm TCU trim length?

[rexican]

Hi, everybody
I just fireformed a few rounds for my 10" 7mm TCU, and I would like to know what length I should trim the cases to.
None of the reloading manuals I own have any information on the TCU, and I have been getting most of my information online.

I want to try out some loads with 4895 and 4759 this week, so I'd appreciate any help.
Thanks

[SandWedge]

Hi Rexican -

From Speer #13:  Max Case Length is 1.749".  Trim To Length is 1.739".  But on the Accurate Powder site, Max Case Length is 1.760".  Lyman manual states 1.750". 

I trim the to the longer number and try to keep OAL as long as practical. 

Good Luck!

Sandwedge

[WayneS]

After forming and fire-forming very seldom are 223 Rem cases anywhere over the max length. , I'ld say either don't bother, or trim all to a uniform length, also look at the Lee collet sizing die. There is no pulling and expander ball back through the case neck which should stop stretching the case

[rexican]

Thanks for the info! I've been thinking about a neck sizer die, but I'll check out the lee collet sizer.

[blpenn66502]

In my experience, when you neck up a 223 case to 7mm TCU the case will shorten about .010 and you'll loose some more length ~ .005 to .010 when you fireform the load.

I would say that a trim length of 1.740 would be appropriate which is what my older references say (Sierra & Lyman).  I think however, as long as your are consistent, it doesn't matter as long it they chamber.

Hornady alludes to IMR 4895 being a good performer.  I've only seen published data on IMR 4759 for cast, nothing for jacketed.

BTW, I don't think Lee ever offered a collet sizer for the 7mm TCU but they do currently sell a case length gage for their trimmer.

Best,
Brian