I had a Vais (spelling?) break installed on my .300 Winmag. Now, I wouldn't shoot the thing without it. It tames the recoil. It cost about $150 bucks to have installed by a gunsmith. It may cost more if they have to pull the barrell off the gun, but hopefully they can do it without such drastic measures.
I have a friend with and without the break on .300 RUMS. I wouldn't bother shooting the RUM without the break.
Terry in Glendale ARizona