Some rifle manufacture's magazines are longer than others, and some cartridges have a longer freebore than others. That is just the way it is. I have loaded for many Weatherby Magnums, and their freebore has never been a problem for me. I have also loaded the 7mm, .300, and ,.338 RUM's which also have freebores with no problems. The whole trick to handloading is uniformity. Try to make each round exactly as the last.

I have noticed thatBrowning A-Bolts have short magazines.

Good luck.