At last count I had nineteen different types of .22 rim fire ammunition. Today, I have to make that an even twenty. Once again I have fallen to the curiosity of an offering previously unknown to me.
This time it was, perhaps, the most unusual .22 rim fire I have seen. Aguila, a company not afraid to offer something different, brings us it's 'Sniper Subsonic' round with a 60 grain solid lead bullet. Yes.... 60 grains. The heaviest .22 rim fire normally encountered is 40 grains. Higher velocity rounds usually drop that to 36 grains, or even 30 grains.
Aguila managed to squeeze that huge slug into a long rifle sized package by taking a unique route. They used a .22 short case, with a reduced powder charge, and loaded a very long lead bullet into it, bringing the whole cartridge out to .22 long rifle length. The SSS round looks the part too, with half the cartridge length being lead bullet. That's more than unusual, it's down right strange looking.
The idea is fascinating, with the heavy bullet retaining substantial energy while the low velocity and charge give greatly reduced noise. The problem with this approach is one of bullet stability.
Heavier low velocity bullets require a rapid twist rate to stabilize the bullet in flight. Lighter high velocity bullets can use a slower twist rate to accomplish the same stability. Bullet design also comes into play in the equation. Even the type of rifling can have an effect.
Typical .22 rim fire firearms shooting a 35 to 40 grain bullet at 1000 fps work well with a 1 in 16" twist rate, and this is standard for these weapons. A .223 center fire shooting a 60 grain bullet at 3200 fps usually works well with a 1 in 9" twist.
A .22 rim fire shooting a 60 grain bullet at subsonic velocities? A rapid twist would be in order, and its doubtful that 1 in 16" will do it. The test is simple. Load an accurate .22 rifle with the new ammunition, sight on a reasonable target, and note the results. That is exactly what I did, and the results are shown here.
The rifle chosen was a CZ452 Trainer, and is exceptionally accurate. It has shown a tolerance for various cartridges, without being overly picky about what it will shoot well. The long barrel and deep rifling may have something to do with that, as well as the tight bore. This rifle, even with open sights, constantly surprises shooters with it's consistent ability to group tightly.
Setting simple 4"x6" card stock targets at 50 feet, several rounds were fired. Only a were needed to answer the basic question. The very first round was a classic keyhole, as was every round after. The Aguila 60 grain bullets simply would not stabilize in the 1 in 16" twist CZ barrel.
Fired at both a paper target and a block of pine, the imprints are clear sideways impacts of a bullet tumbling in flight.
Perhaps this ammunition would be better suited to a .22 wearing a custom rapid twist barrel, as many folks have fitted to Ruger 10/22s. Also, it might be a perfect round for an AR equipped with a rim fire conversion, especially if it has a suppressor can installed. For my .22's, all of which have 1 in 16" twist barrels, I'm afraid this Aguila offering is useless.
Light loads, mixed results - After some more reading, decided to try sizing the bullets to .311". Also to try a recommended load in .30-06 of 3.2 grains Bullseye, and in .30-30 2.7 gr...
7 minutes ago