300 Win Mag Cartridge length

[Kilkenny]

I have been loading for my 300 Win Mag in a Weatherby Vanguard for years with fairly good results. Will usually get sub MOA groups with 73.0 gr RL19, 215 primers and 165 gr Barnes TSX BT at 2994 fps. (I do more hunting than long range target shooting, but have shot my last two deer at 454 and 468 yards). For some reason I never questioned the data of a Cartridge OAL of 3.340 when I started reloading for this rifle. I just bought a new Cooper rifle in 300 win mag and noticed excessive room in the magazine on this rifle, so was going to reload with the bullets just off the lands. To my surprise I just had to barely stick the bullet into the case and it fed into the chamber. After checking SAAMI this caliber has quite a bit of free bore. Does anyone have better luck seating the bullets clear out on this caliber or better accuracy seating to std OAL lengths?