As far as safety is concerned it is not the OAL that maters, it is the seating depth that makes a difference.
More to the point, it is the free volume under the bullet that is important. More volume, all other things being equal, less pressure. Less volume, more pressure.
Since we cannot measure the volume under the bullet, or even the linear distance from the case web to the bullet base (assuming a flat base), we depend on the cartridge length as a proxy to the measurement we wish to control.
Since the ammunition makers know the bullet length and shape and have signed on to the (voluntary) S.A.M.M.I. specifications, they (in theory) take into account stuff many handloaders take on faith (how many of us measure the length of a bullet, the depth of the web of all our different brands of brass and subtract that from the Cartridge OAL?).
Much less, how many of us pay attention to the chamber dimensions of the test guns from which the loading manuals derived their data, even if that information were available?
Rather than pick over the details, we watch our own brass, primers, leading and other diagnostics to see how much pressure our particular guns generate. This is why we start low and work up.
Be safe, always, all ways.
Lost Sheep