There has been quite few responses reguarding shot making. I personaly have made shot four 4 years and at this point I dont think it has helped or improved my scores. I use a shot maker. and use all kinds of lead. However, if using tire weights---- remove the stick on type and the zinc alloy
good news, its not very hard but there is a learning curve. It need not take a lot of time. As long as you have some extra time. I make my shot in 50lb batches. I can turn on the shotmaker,set up,drop shot,clean,rinse and while it dries clean up put everything away about 1.25 hours.
Bad points....source of lead I get 90% of my lead for free. Wheel weights,range scrap and from the shot field on the trap range< this is kind of sucky BUT a good hour with a medium sifter I can yeild about 100lbs then smelt it down makes nice shot.
There are a few good threads going on here on TS.com
Also there is a good amount on castboolits.com, shotgunworld.com
Once I get some power lines to the barn I will be trying a shot tower. It all depends on what the outside temp is. If its to warm or hot it will not work but if its to cold it will not work. The temp I was told is the high 50 and in the 60's will work well for size 7 1/2 shot. The tower for smaller shot doesn't have to be 200+ feet but 20 to 25 feet.