Fit ammo to your chamber and to your mag length. SAAMI applies to manufacturers, not hand loaders. I never look at book spec max length, since I will have my own max length based on my chamber.
Yup
Shape of the bullet and mag length comes into play as well as your rifle. Some rifles like Weahtherby rifles have as much as .25 free bore so with them you are not going to be seating near the lands and still function through the mag. The further out you have a bullet seated the more room there is for powder, but when kissing the lands there is not room for a bullet to have a jump and pressures will build up quickly without that jump. For instance in a Remington 257Wby we were blowing primer pockets with factory loads while a Weatherby rifle no blown primers or excessive pressure indicators. Difference in the rifles was that extra free bore in the Weatherby chamber. Just something to think about.
Work up in powder charge from low to higher and find a good shooting load without pressure signs and have fun. I usually do this starting kissing the lands with Bergers and .1 of caliber off the lands with most others if mag length and bullet allow it. Part of that bullet allow it thing, I want at least a caliber length in the case neck for proper neck tension so if a bullet is too short for a full caliber of seating depth then there will be more of a jump for where I load from on the bullet jump into the lands. Also for all other than single shots Mag length will dictate max coal, if I want a single shot I will shoot one.
Hope this is not too confusing just my
Kevin!