Obviously that is subjective to the size of the deer, but most people say the vitals of the average deer is about like an 8" circle.

If you still have a problem with that gun shooting the way it does, you may want to try different choke tubes as well as what I said earlier with different brands of ammo. In general the slugs will group tightest with an improved or open choke, but some people like a modified. Normaly a full choke won't shoot worth beans (it deforms the slug), and I wouldn't try it with an older gun but sometimes a full will shoot good.

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