I don't really shoot long range but our deer are a lot smaller and at 250yards you need to be very precise.
I don't use a bipod as I find there are too many variables when it comes to field usage. The hardness of the surface varies, the angle is uneven, unless you're going to cant legs must be adjusted and the darn things are loud and uncomfortable to carry.
I choose to ball up my soft back pack (used for carrying back the carcass) and use that as a rest. It works very well and eliminates another piece of equipment.