I have one of D rock's tools and it works pretty good for me. I tree squirrel hunt alot so I have been trying to find the prefect squirrel bullet I have tried target bullets but they were not working, I had one squirrel that I had to shoot three times in the head and I still had to run it down.
I used sub sonics but the only come in deep hollow points and they were doing to much meat damage if I made a chest shot so I ended up just using CCI SGBs but they are high velocity and ended up scare the other squirrels in the tree so I'm hoping to be able to make some custom bullets for hunting that are subsonic and meat friendly.
Here are some hollow points with different depths they started out as Aquila super extra solids (the second one from left is a Remington subsonic that I made the hollow point bigger).

and this mushroom is the deepest one after I shot it in wet newspaper @ 30 yards,it made a 1'' hole in the paper

This is a EPS wadcutter with a mushroomed bullet next to it from paper test @ 30 yards. I think this one will make a good squirrel bullet but I will have to a month for season to come in to find out

I'm not saying that you can make a better bullet then what you can buy. but what you can do is make hollow points out of the ammo that you have on hand and make it fit your needs. You also get a round nose and flat nose die in the set.