Practically every P14, regardless of manufacture date or factory will have groove dimeters of .3125" or larger. I have slugged a couple that were at .3153" This is usually NOT due to wear but the nominal groove diameter of the 303 Brit is .313" ( .303 bore +_ .005 groove depth x2 = .010 Total .303" + .010" = .313" Do keep the brass fron your Lee-Enfields separate from your P14. The LE action, while strong enough, tends to be a bit springy, and warm loads will reduce brass life dramatically. The P14 is a front locking action of substantial strength, and will digest loads that would be poison for a LE. There is a caution out there for the ERA built P14's, since the heat treatment was suspect, but the Remington and Winchester units have no such problem.
I have a 1916 vintage Winchester-built P14, and while I have not used much 4895 in it, my pet loads are as follows; 150 gr., 44/45 grains of N540, depending on bullet. 174/180 grain 49/50 grains of W760, again depending on bullet. These loads challenge the 308, and are very accurate in my rifle. As a matter of fact, My 150 Hornady load will shoot under 1" @ 100 meters consistently. The usual caution applies,Work up these loads from 5 grains below, watching for any undue pressure signs. My brass lasts a long time, some have been fired 9 or 10 times with no incipient separations, and no primer pocket issues. I shot two deer with mine last fall, one with a 180 Norma Semi spitzer (.312"), one with a 180 Sierra Pro-Hunter Spitzer (.311") Both were one-shot kills, and I was very pleased with the performance. Regards, Eagleye.