The Max COL listed in manuals has very little to do with your particular firearm. Each firearm will have it's own max COL. The Max COL listed in the manuals is for ammo manufacturers so as every round sold will fit every firearm made. The handloader is free to adjust the COL to fit his or her specific needs.
From Accurate Powders..
SPECIAL NOTE ON CARTRIDGE OVERALL LENGTH “COL”
It is important to note that the SAAMI “COL” values are for the firearms and ammunition manufacturers industry and must
be seen as a guideline only.
The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination.
This parameter is determined by various dimensions such as 1) magazine length (space), 2) freebore-lead dimensions of
the barrel, 3) ogive or profile of the projectile and 4) position of cannelure or crimp groove.
From Hornady #7