I have several chickens, and their coop is infested with mice. I transformed my flat headed lead pellets into sharp hunting pellets. Bbs and flat nosed pellets wouldn't always kill the mice with one shot ( they are fairly big), but these pellets almost always get the job done with a single shot. The materials needed are: -flat nosed pellets -small headed nails -wire cutters - super glue I am not reliable for any injuries or damage caused by these pellets.

Step 1: Cutting the Nails

Using the wire cutters, cut the nails right near the head. The wire cutters do not cut the nails evenly, so a sharp edge is left on the nail near the head. The picture with the pellet shows what the cut nail should look like (left). Make sure to keep the end of the nail with the head.
<p>I like the idea but wouldn`t it harm the rifling of the barrel?</p>
It's just me but I'd take less knock down and have a move accurate shot cause no matter how much knock down power you have its only worth anything if you can place it where you need it.
as far as ballistics go i can only see these decreasing accuracy and velocity. but i will give you the increased penetration, its just that if you want more damage\knockdown (for mice?) then use softer lead pellets or a hollow point for increased expansion