M138 Experimental .358/.44 Invicta Cartridge with Black Adapter
Description: This is a variation of the .358/.44 Invicta cartridge manufactured by the Olsen Development Lab of Eagleville, Pennsylvania. The cartridge concept and associated revolver system were developed by Charles R. Olsen, who held two related U.S. patents: U.S. Patent No. 4,393,782, "Revolving Firearms and Ammunition Therefor,” issued July 19, 1983, and U.S. Patent No. 4,457,093, "Revolving Firearms,” issued July 3, 1984. Together, these patents addressed several persistent issues in revolver design and ammunition performance.
The primary objective of the Invicta system was to eliminate gas loss at the cylinder-to-barrel gap, thereby increasing muzzle velocity while still using a straight-wall cartridge case. The design also aimed to reduce carbon buildup on the cylinder face and frame, improving long-term reliability and reducing maintenance issues. Olsen’s approach used a conventional straight-wall case loaded with a slightly smaller-diameter bullet housed within a sliding plastic adapter. Upon firing, the adapter moved forward to seal the cylinder gap while the bullet traveled down the barrel. After the bullet exited the muzzle and pressure dropped, the adapter retracted into the cartridge case, allowing normal cylinder rotation and extraction.
The associated revolvers incorporated specially designed "inhibiting chambers” that prevented standard full-caliber ammunition from being fully chambered or fired, reducing the risk of incorrect ammunition use in modified, reduced-bore firearms. Despite its technical ambition, the Invicta system was never commercially adopted and remained strictly experimental.
This example consists of a flat-nose lead bullet, apparently unjacketed, housed within a black plastic adapter. The adapter is retained in a slightly necked brass case featuring a single smooth cannelure and fitted with a nickel primer. This cartridge represents one of the experimental .358/.44 Invicta variations developed by the Olsen Development Lab of Eagleville, Pennsylvania. A nice representative example of the .358/.44 Invicta cartridge, one of several known variations produced during development of the Invicta revolving firearm and ammunition system.
Headstamp: "R – P / 44 REM MAG”
Measures: OAL 1.803” CL 1.285” RD .509” HD .453” CM .438” BDaCM .433” Weight 308 Grs.
Price: $45.00 UPS Shipping Required
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American Civil War Relics &
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