You should not have to change calibers as the weight of the bullet could be the same or even heavier in a smaller caliber rifle. We seldom lose more than a pound or two of meat from the deer we process. The problem is that most people discard the area that was hit instead of taking their time to scrape the blood clots away and salvage the usable meat. Most of the time the impact of the bullet causes the blood to gel between the layers of meat and can be scraped off. (See our visual aids page on the website.)
    As far as cooking if you're talking about steaks and roasts then you may be leaving too much of the fat cover on the meat.
If you're talking ground venison then you may have made the mistake that a lot of people do by adding beef or pork fat to the venison when grinding. We only recommend and use pork shoulder butts and Ground Chuck when adding to venison.

Happy New Year,

Dave