For hunting, and even beyond 500 yds, load testing off of a bag platform is
surely good enough. You are not wasting your time.
The main thing is that you are able to hold the gun dead steady, and it recoils the same each shot. Set your bags up so they dont "rock" back and forth when the gun recoils. Ideally, you want the gun to sit in the same place on the bags every shot, and try to apply the same pressures to the stock every shot.......................it's all about consistency.
If you are using the bags correctly, 1/4 moa accuracy or better is obtainable, assuming the rifle/load is up the the task. Even if everything is not perfect, 1/2 moa is easily done off "just bags", again assuming the gun is capable.
Once you get a load developed that consistently shoots 3/4 moa or better extreme spread, practice under field positions, ex bipod and rear bag, and make sure of your point of impact at distance.
You are GTG!