The .22 K Hornet
By Chuck Hawks
Lysle Kilbourn created the "Improved" .22 K Hornet in 1940 by fireforming (blowing out) a standard .22 Hornet case. The result was a rimmed, bottleneck case with no body taper, a sharp 40 degree shoulder, and a shorter neck. Its powder capacity was considerably increased and along with it the muzzle velocity (MV) attainable with all bullet weights. This little wildcat became very popular and has been mentioned and written about by many famous gun writers over the years.
It is a pretty simple matter to have a gunsmith rechamber a .22 Hornet rifle for the .22 K Hornet. .22 Hornet factory loads can then be fired in the improved chamber and out comes .22 K Hornet brass for reloading.
Note that different versions of the K Hornet have different neck lengths. Another K Hornet variation is slightly shortened to work in S&W revolvers. These variations affect the maximum average pressure (MAP) of the load, and are points anyone reloading for a K Hornet rifle should keep in mind. Like any wildcat, the dimensions of the .22 K Hornet are not standardized, nor is its pressure limit.
The SAAMI MAP pressure for the .22 Hornet parent cartridge was originally 47,000 cup. In recent years this has been lowered to 43,000 cup. It would seem wise to not exceed the old 47,000 cup limit in any K Hornet rifle.
Here are the specifications for the .22 K Hornet as they appear in the 6th edition of the Hornady Handbook of Cartridge Reloading: Maximum COL 1.723", Maximum case length 1.403", neck length .243", rim diameter.350", bullet diameter .224".
Rifles that have been rechambered from the standard .22 Hornet to .22 K Hornet usually have 1-16" twist barrels and will not stabilize bullets heavier than about 52 grains. In most rifles, 45 grain bullets give good accuracy and performance. Remember that, although blown out, the .22 K Hornet is still a small capacity cartridge.
The Hornady Handbook shows that a reload using their 45 grain bullets in front of 12.0 grains of AA 1680 powder delivers a MV of 2400 fps. A maximum load of 15.1 grains of AA 1680 can drive the same bullets to a MV of 2900 fps. These loads used WSR primers and reformed Hornady cases and were tested in a 24" T/C Encore barrel.
That maximum load is 300 fps faster than the top load for the standard Hornet. Such maximum loads move the .22 K Hornet into the ballistic category of the .218 Bee. However, .22 Hornet brass is quite thin and does not have the case life of most centerfire .22's. Always inspect all brass carefully for incipient head separation before reloading.
Copyright 2005, 2014 by Chuck Hawks. All rights reserved.