This is a topic we love here at SimpleShot because we think that shooting BBs is one of the best things you can do to improve your accuracy. Shooting BBs gives you feedback in a way that shooting larger ammo never will and you can massively improve your accuracy shooting BBs.
The question about a BB frame is simple. Any slingshot frame can be used to shoot BBs. It is common for shooters to use a small frame, but it is absolutely not necessary. You can shoot BBs from the Hammer if you like.
The more important question is that of bands. It is always essential that you match your band set to your ammo. If you do not match your band set to BBs, you will definitely lack accuracy and enjoyment. Make sure you use a properly matched band set for small ammo.
Then enjoy shooting small ammo with small bands. The draw is easy. The ammo is cheap. BBs are great for shooting paper and will help you shoot better in many ways!
We love BB shooting with slingshots and highly recommend it!