When Ozz was in the Navy years ago, they had battle ships with 16" guns. Is it the pictures, or my computer monitor but shouldn't that target be a little bigger for 16" shells? And maybe some framing and an axle or two to tow it around.
Finally, if Ozz uses one of his spare 16" guns for prairie dog shooting he won't need a scope or any rifle or that target for that matter. A shot anywhere close to the prairie dog colony should be able to pretty much take them all out with the one shell. Just make sure you are not near a residential neighborhood when you do it. The residents might get upset at the noise and all the prairie dogs dropping out of the sky and into their yards.