22 Hornet Primer Study M.L. McPherson
Tested propellant charges in cases, left-to-right: Alliant Power Pro 300-MP, 15.0 gr.; H110, 14.9 gr.; Lil’ Gun, 13.8 gr.; and IMR 4227 (Canadian made), 12.8 gr. Interestingly, I dropped all these charges with the same measure setting. Different granule size and shape results in variations in packing density, depending upon container shape. In terms of mass required to fi ll the case, 300-MP packs best in the Hornet, H110 comes next, and H4227 fi nishes last.
Synopsis: While it might seem
that handloaders have a surfeit of primer choices and that, therefore, we should have the ideal primer for every application, a moment of refl ection on the vast range of case capacity, pres- sure levels, and propellant properties with which we routinely work will put the lie to that assumption. Usable case capacities vary from about 3 grains of water to about 160 grains of water and propellant burn rate varies across a range of 20 times. Therefore, we have nowhere nearly the primer selection that we need. Particularly, we do not have primers that are energetic enough for the largest cases using the most heav- ily deterred (most diffi cultly ignited) propellants and we do not have primers that are mild enough for the smallest cases using the least heavily deterred (most easily ignited) propellants. BACKGROUND
The 22 Hornet is the epitome of a
too-small case for the available primers. Not only because it uses relatively small charges of relatively easily ignited pro- pellants but also because it has so little neck tension — the blast from any but the mildest of primers is almost certain to dislodge the bullet before ignition be- gins, which always degrades accuracy. With this in mind, I have always recommended use of pistol primers in
Hornet fi rearms that will tolerate these (blanking and piercing can occur in guns with, respectively, very light and very heavy striker impacts). I have conducted some experimenting with primers in the 17 Ackley Hornet and the 22 K-Hornet cartridges. But, until now, I have never conducted a rigorous primer test in the 22 Hornet case. ANALYSIS OF MEANING OF RESULTS Chronograph data indicates de-
gree of ballistic uniformity. Other than the limited number of shots, this result is robust: Those combinations of primer and propellant that generated smaller standard deviations are most likely to be good choices; conversely, those that generated larger standard deviations are most likely to be bad choices. The single caveat to this asser-
tion is that it is possible that variations in loading details could change neck tension suffi ciently so that some com- binations could work better and other combinations could work worse. I did everything I could to minimize these issues in the tested loads. I used a 0.222- inch expander, to provide signifi cant neck tension without deforming the bullet. I used a bullet with a long shank, to maximize neck tension. I used a bullet with a hard core, to maximize rifl ing engravement force and thereby to minimize how far the primer blast
Tested load: Remington case with Barnes 30-grain Varmint Grenade loaded at 1.78-inches overall length, to give 20/1000-inch bullet-to-rifl ing jump in the CZ.
might move the bullet. I seated the bullet 20/1000-inch from the rifl ing, because we
know that 20/1000-inch bullet-to-rifl ing jump is a good fi rst-guess toward con- sistency and accuracy. Overall, I believe that it is fair to
suggest that the results of this study are indicative of what anyone could expect when using these propellants with any bullet in the Hornet.
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