The service issue version was made by Ithaca and differed only in a shorter barrel length. Somewhere online is a complete military user's manual. It was designed for the USAF primarily for arctic flights vs the USSR. For this the light wieght and caliber sufficient for rabbits,ptarmigan and other small game encountered north was perfect. It was this military experience with the .22 Hornet that gave more impetus to 5.56 development. Survival school in Alaska actually had a trap shooting session with the little rifle. The .22Hornet in any commercial load is at best average in accuracy in this rifle. The primary problem lies in using small rifle primers which are far to violent to initiate a good burn rate. Handloading with pistol primers dramatically increases accuracy. There is a wildcat called the 'K Hornet' with the tapered case straightened out. You can gain some velocity, but better yet simply maintain or even slightly reduce loads for lower chamber pressures. Standard loads can still be used and the cases fireformed.