it seems like the #4's are your only bet with the .410. anything smaller with a sawed off barrel yield a looser pattern. i would pattern it if you can but i would also try to get my hands on a 20 guage if at all possible.

as for deer..... keep a look out for 000 buckshot for that thing. 000 size balls fit the shaft of a .410 shell perfectly and are almost like 3 slugs lined up in a cartridge. we have a .410 bolt in the family that is a slayer with those shells. i killed my first at age 7 with a single shot, my brother at 9 with one shot, and my little cousin got his first with it this past season!