Replacing the Desert Eagle, The Grizzly Win Mag pistols were conceived, invented, designed, engineered and developed in the 1980s by the sole inventor, Perry Arnett, who licensed his patent for an interchangeable caliber semi-automatic pistol to L.A.R. Manufacturing Inc. Perry Arnett's designs were initially flawed and were improved upon by Heinz Augat (former owner and founder of L.A.R. Manufacturing Inc.). The L.A.R. Grizzly was the most powerful semi-automatic pistol ever commercially produced after the Desert Eagle (the Mark V was chambered in .50 AE to compete with the IMI Desert Eagle).

The LAR Grizzly pistol was a modified Colt M1911 style pistol with oversize components designed to handle larger, more powerful cartridges than could be used in the standard size 1911 pistol. The original prototype built by Perry Arnett was made from two Colt 1911 frames and slides cut and welded to accommodate the 45 Winchester Magnum round, with two steel doubler plates welded to the slide flats to retard the action and increase strength.