Free: Contests & Raffles.
150 grain is fine but I'm not sure the type of bullet you're using is the best. For the perfect broadside shot behind the shoulder it will work, but if shot placement and/or the angle isn't ideal, you'd be better off with a "premium" bullet. Something like a Nosler Partition or any of the bonded bullets would be great, even if they are in a lightweight 150 grain. If you do use the standard 150 grain bullets just be very careful about shot placement. (You probably don't want to try shooting through a shoulder)