The Huntsman requires federal paperwork mainly because of barrel interchange ability as Cayugad has mentioned, however it is built on the SB1 action which will only accept shotgun barrels not including the 10 gauge.Handi-rifles can be purchased as a .243/.50 caliber combo package - in that instance the SB2 action is used (that is their centerfire action). The SB2 will accept a muzzleloader barrel while the SB1 will not be fitted with a CF barrel.

The Sidekick was H&R's effort at marketing a "Huntsman-like" muzzleloader ONLY that will not accept alternate barrels of any sort (by them) and therefore be available online, via mail, or over the counter without the paperwork requirements. As Cayugad indicated, the Sidekick action is a bit shorter but otherwise houses veryfew differences from its older brothers. Sidekick barrels are most commonly 26" but a 24" model is still available. The Huntsman barrels are 24".

Another difference is the powder handling capability of the rifles - the Sidekick is capable of handling so-called "magnum" loads while the loading limititations for the Huntsman are more restrictive. This is something I find puzzling, but true.

I own an SS/Nickel Huntsman that has the finest trigger I've encountered on any muzzleloader straight out of the box. I don't think you would go far wrong with either model, particularly if you only intend to use the rifle as a muzzleloader.They represent perhaps the best value available in their price ranges and most owners are amazed by their consistently good accuracy with a multitude of loads.

Both have quirks and a few issues that H&R could easily solve, but I guess they do not see the need.