The Tac-M79 can be configured in a variety of ways. A version that has proven to be very popular with law Enforcement and Reeactors is the "Breacher" configuration. This version combines a 6" barrel with the tactical configuration of the Tac-79.
The other configurations are below

This is a level of flexibility in a 37mm launcher that has only been dreampt of until now. Just Wow!
The Short Barrel version of the launcher does not come with any picatinny rails, the barrel is plain and undrilled.
The basic specs of the Tac-79 are as follows:
Designation: Launcher, 37mm, Single Action, Exposed Hammer, Top Break, Pistol Configuration
Country of Origin: USA
Manufacturer: Ordnance Group LLC, Sarasota Florida USA
Caliber: 37/38mm (1.5”) Rimmed Ammunition
Barrel Length: 6” (15cm). Fully enclosed rim. Transverse pin lockup
Dimensions (Tactical configuration):
- Length 11in. (28cm)
- Height 7.5in (18cm)
- Weight 2lb 6oz (1.1kg)
Nominal Trigger Pull: 1.5lbs (0.7kg)
Safety: Ambidextrous Hammer Block
Stock: None
Foregrip: None
Pistol Grip: A2 AR compatible grip
Materials: 6061-T6 Aluminum. 4140 Steel. All materials sourced from the USA
Finishes: MIL-A-8625 Type II Anodizing and Mil-DTL-13924D Black Oxide
Picatinny Rails: Special order
Drilled and tapped to accept any AR compatible butt stock using only the buffer tube, castle nut and alignment plate. Buffer and Buffer Spring are not required.
Download the complete specs here