NO!, NO!, NO!. Regular sizing dies will work just fine. In my wife's BAR 30-06, I only neck size the cases for the first 5 reloads, then I "bump" the shoulder just a tad for the next 5 at which time the cases are canned.
Small base dies are for lousy chambers, they shorten case life.
The chambering power of a BAR is very strong. NEVER ease the bolt forward on the first shot, let it slam and the subsequent ones will handle themselves.
There is a case to be made for only hunting with premium factory ammo (after testing each one to be sure it chambers) in a semi-auto. I do not and have never had a malfunction in the BAR at the range or in the field. The same is true of these:
Bennili R1 in 300 winmag, Merkel SR1 in 9.3x62 and DPMS LR 300 SAUM.