I just bought a new training pistol (starter pistol, blank pistol) from gun dog supply (http://www.gundogsupply.com). After visiting with them about the different options they have, they were very helpful, I decided on the Kimar 209 primer pistol Made by Traditions. I couldn’t be more happy with it. It has a solid feel to it like a real pistol, is loud without being too loud and fits nicely in an Uncle Mike’s Sidekick holster. Also, the 209 primers are cheap and easy to come by. It also comes with a nice plastic case. (I can see that the latches won’t last too long on the case, but it’s a nice touch.) It was a great buy for the money.
Pistols are nice to train with because they can be on your side, grabbed quickly when you want a gunshot, then put away so you have two free hands. If you want to train with a pistol, but can’t justify buying one the few months you’ll need it to train just one pup, if you have a .22 pistol, you can use it. Revolvers, like the Ruger single-six work particularly well with blank loads. (Ah, maybe a good reason to buy a new gun!) Simply use your .22 and purchase .22 blanks. Trust me, even though blanks may cost more than loaded shells, buy them so you don’t have to worry about where the bullet is going to end up. You’ll have enough on your mind training the dog. As a side note, if you buy crimped loads, like for a ramset concrete nail gun, there is some debris (probably acrylic glue in the end of the shell) that shoots out, so don’t point it at anything close.
Another is to make your own shotgun popper loads. If you have a shotgun reloader, simply reprime shotgun hulls and don’t crimp them. These work well in an over/under. If you have a pump, cut the crimp off and they should feed through the magazine fine. This works very well, helps the dog learn to look where the shotgun is pointed and it’s not quite as loud as a pistol. This is a great tool, one that I love to use with young puppies, but I often find myself having to lay my nice shotgun down on the ground so I have use of both hands, then it gets stepped on by a pup.
A final alternative is to use your muzzleloader with only the 209 primer or the cap. This will work just as well as the shotgun popper loads, except that you can shoot twice and they are a pain to clean.