I’ve gotten a few emails like this:

There is no getting around the laws of physics – every action has an opposite and equal reaction.
For this unit to impart that mass with that speed, something of that magnitude would be needed in the recoil.
a 30/06 at 3000 fps – 100 gr or 100/480 ounce would exert 39 ft/lbs of force (moving a 39 lb shoulder 1 foot).
Never mind pistol grips – this would need concrete reiforced beams. (unless the projectiles are self propelled – mini rockets)
Anyways, my scam meter is on reddish orange.