Well, the actual powder charged used might just come into play...?
The MAX OAL for 10mm is, as previously stated, 1.260". Almost all Hodgdons load data for 180gr bullets (the exception being the XTP?) is at that suggested length.
How they fit in your magazines, chamber, etc. will be yours to determine. Any clue as to how hard they are?
Cheers!
P.S. I load a similar bullet from MBC (IPD #5, Brinell 18) in both 10mm & 40 S&W with fine results a bit shorter than the MAXs...