January 04, 2011
When it comes to delivering the entire package--accuracy, trajectory, energy, and the ability to buck wind--the .17 Hornady
Mach 2 outguns any .22 Long Rifle load presently available.
Years ago, I often traveled to and from Europe and the Middle East on both the British and the French Concorde airliners. A large monitor at the front of the passenger's cabin constantly indicated in large green letters the speed of that wonderful airplane.
As the sleek craft leveled off at just over 58,000 feet at the beginning of my very first 3.5-hour flight from Washington to London, "MACH 2.04" flashed on the monitor. So I whipped out my portable calculator and started punching its keys.
Always a shooter at heart, I was curious to compare my twice-the-speed-of-sound velocity to that of a rifle cartridge. I remember the thrill I felt when the little instrument in my hand showed me I was traveling faster than a 170-grain bullet fired from the .30-30 Winchester by a deer hunter who might be standing miles below me.
I was reminded of those long-ago Concorde flights when I first heard about a new cartridge from Hornady called the .l7 Hornady Mach 2 (HM2). How they came up with the name is no great mystery. The speed of sound traveling through air at sea level is said to be around 760 miles per hour, or 1,115 feet per second, so Mach 2 works out to roughly 2230 fps. Hornady rates the itsy bitsy cartridge at 2100 fps, so if we flatlanders want to be technically correct, we would call it the ".17 Mach 1.9" or something like that. But since that moniker sounds as awkward as calling the .44 Magnum the .429 Magnum, Hornady wisely chose to make things short and sweet by naming it the .17 HM2. That worked out quite nicely since it is indeed a sweet little cartridge--and it is also quite short.
ACCURACY & VELOCITY COMPARISION
|FACTORY LOAD ||VELOCITY (fps) ||100-yard ACCURACY (in.) |
| ||.17 HM2 Kimber 17 Pro Varmint, 20 Inch Barrel |
|CCI 17-gr. V-Max ||2083 ||1.25 |
|Eley 17-gr. V-Max ||2178 ||1.37 |
|Federal 17-gr. V-Max ||2155 ||0.95 |
|Hornady 17-gr. V-Max ||2113 ||1.29 |
|Remindton 17-gr. AccuTip-V ||2108 ||1.18 |
| ||.22 LR Kimber 22 Pro Varmint, 20 Inch Barrel |
|CCI 32-gr. Stinger ||1634 ||2.01 |
|CCI 40-gr. Velocitor ||1364 ||1.36 |
|Federal 40-gr. Classic ||1236 ||1.19 |
|Remington/Eley 40-gr. Match EPS ||1064 ||0.71 |
|Winchester 38-gr. Power-Point ||1282 ||1.20 |
|Notes: Accuracy is the average of five, five-shot groups fired from a sandbag benchrest at 100 yards. Velocity is the average of 25 rounds measured 12 feet from the rifles' muzzles. |
Just for the fun of it, and to give people who take life far too seriously something to complain about, I will also point out that whether or not the .17 HM2 lives up to its name in velocity depends on who is shooting it and where it is being shot. Since the speed of sound decreases as elevation above sea level increases, the 17-grain bullet fired from the rifle of a Sherpa porter standing 29,000 feet above base camp on Mount Everest would actually leave the muzzle at a speed greater than Mach 2.
One thing is certain, if the speed at which rifle and handgun manufacturers geared up to start chambering for the .17 HM2 could somehow be measured, it would likely prove to be even faster than twice the speed of sound. Quicker than you can say, "I love the .17," each and every manufacturer of .22 rimfire rifles and handguns was cha
mbering for the little round.
Bolt-action rifles from Kimber, Anschutz, and others came first simply because converting a bolt gun took no more effort than decreasing the size of the hole in its barrel. Blowback-operated autoloaders took a bit longer after it was revealed to the industry by CCI/Speer that time-to-peak chamber pressure for the .17 HM2 differs from the .22 Long Rifle.
In addition to causing bolt-cycle speed of an autoloader designed for the .22 LR to increase beyond an acceptable level, it could also cause the bolt to open prematurely, allowing a fired case to start moving from the chamber before pressure had dropped off. In other words, converting a semiautomatic in .22 LR to .17 HM2 required more than barrel replacement. The problem has been solved by either increasing the weight of the bolt directly or by indirectly adding weight to the bolt by linking it to a reciprocating weight hanging from the barrel and located inside the forearm, as Thompson/Center has done with the R55 rifle.
The .17 HM2 is the .22 LR Stinger case necked down for a .172-inch bullet weighing 17 grains and with a ballistic coefficient of .125. The Stinger was introduced by CCI in 1977, and its muzzle velocity of 1640 fps with a 32-grain bullet quickly added the word "hypervelocity" to the vocabularies of .22 Rimfire shooters around the world. Maximum overall lengths of the regular and Stinger versions of the .22 LR cartridge are the same at 1 inch. Powder capacity of the Stinger is greater due not only to its 0.100-inch longer case but also because it's shorter 32-grain bullet does not displace as much area within the powder cavity as the standard 40-grain bullet of the regular .22 LR. The increase in net case capacity of the Stinger allows the use of a relatively heavy charge of slow-burning powder for a muzzle-velocity increase of about 30 percent over the standard .22 LR. Yet chamber pressure is the same as for the high-velocity loading of that cartridge.
Use of the Stinger case in developing the .17 HM2 enabled engineers at Hornady to safely push a 17-grain bullet beyond 2000 fps from a 24-inch barrel without exceeding the maximum chamber pressure level of the .22 LR. The velocity they achieved is 150 to 200 fps faster than the .17 Aguila, which is on the standard-length .22 LR case. Overall length of the .17 HM2 is the same as for the .22 LR, and that along with the fact that it works fine in most magazines originally designed for the .22 LR helped to pave the way for manufacturers of repeating rifles to quickly adopt the new chambering.
All loads presently available are loaded with the Hornady 17-grain
V-Max bullet, and they vary in appearance only by the color of their plastic tips: red for Hornady, gold for Remington, blue for Eley, and black for both CCI and Federal (you can tell the CCI and Federal cartridges apart by their "C" and "F" headstamps). Hornady and Federal ammo is loaded by CCI, whereas Eley loads Remington ammo. The Federal and CCI loads are rated 90 fps slower than the others (2010 fps versus 2100 fps), but on my chronograph, both kept pace with their competition. Depending on the rifle from which they were fired, all loads exceeded their factory velocity billing by as much as 50 fps, with the Federal and Eley loads proving to be fastest.
How The .17 HM2 Stacks Up
My first field experience with the .17 HM2 took place during autumn of 2004 while hunting fox squirrels in Kansas with Hornady ammunition and a preproduction T/C R55 autoloader. I have also civilized a few prairie dogs with Federal ammo and a switch-barrel bolt-action Sako Quad. Added to the list are a few gray squirrels, cottontails, jack rabbits, flickertails, starlings, and one very unlucky lizard that a friend said I could not possibly hit at a laser-ranged 94 yards.
I mention all of this to emphasize the fact that I know a bit more about the performance of the .17 HM2 than how it performs on paper targets or how it looks in a company catalog. Some of my adventures were made even more educational by the fact that I shot the .22 LR Stinger and Yellow Jacket loads right alongside the .17 HM2.
My experiences in the field with those cartridges revealed a number of things about their differences, so the next logical step was to see how they stacked up on paper and in front of the chronograph. The test rifles I used were Kimber Pro Varmints, and both wore Bushnell Elite 4300 4-16X scopes. Using near-identical rifles from the same manufacturer reduced the number of variables that might have influenced the outcome of my comparison of the two cartridges.
Comparing how the .17 HM2 stacks up against the .22 LR, I first come to the noise factor. Ear protection should be worn when any firearm is fired, but I see more people shooting rifles in .22 Rimfire without ear protection than with it. Using ear protection when shooting a rifle in .17 HM2 is even more important because its report is both louder and sharper than regular high-velocity loadings of the .22 LR. Hypervelocity loads such as the CCI Stinger and Remington Yellow Jacket narrow the decibel gap a bit, but the newest .17 on the block is still louder.
The .17 HM2 operates at relatively low velocities, and for this reason, its bullets leave very little copper jacket fouling in a barrel with a smoothly finished bore. However, it will build up rather quickly in a rough bore.
I have yet to use a copper solvent in my match-grade barrels, but fouling of another kind will need to be kept under control regardless of the condition of the bore. Due to the relatively slow burn rate of powders loaded in the .17 HM2, propellant fouling seems to build up faster than with .22 LR loads. I do not find the buildup from a couple hundred rounds to have a detrimental effect on accuracy, but it tends to accumulate rather quickly in the chamber. So to assure reliable functioning of an autoloader, it will need to be cleaned more often than a bolt-action rifle. The best bet is to clean with a good powder solvent every 250 to 300 rounds, and since a slight amount of wear or damage to the rifling at the muzzle can harm accuracy rather seriously, a pull-through cleaner is the way to go. The bores of other types of rifles are best cleaned from the chamber end, and a cleaning-rod guide should be used to protect the rifling at the throat from wear.
Ballistic coefficients for the 17-grain bullet of the .17 HM2 and the 40-grain bullet of the .22 LR are close to the same, but the .17-caliber bullet shoots flatter because it starts out considerably faster. Its high velocity also enables the .17-caliber bullet to deliver the same energy levels downrange, even though it is 35 percent lighter.
The .17 HM2 strikes a 100-yard target with around 90 foot-pounds of punch, which is about the same as for both high-velocity and hypervelocity loadings of the .22 LR. However, it does fall short of the 110 ft-lbs delivered at that distance by the CCI Velocitor and its 40-grain bullet at 1435 fps. Also, I have found the .17 HM2 to be less sensitive to wind than the .22 LR Stinger.
Within its effective range, the .17 HM2 offers plenty of punch for hunting small game. Fox squirrels are tough critters, but the first two I toppled from the limbs of the same tree appeared stone dead before they reached the ground. Both took a 17-grai
n bullet through the lungs at exactly 61 yards, and damage to the eating part was no worse than with .22 LR hollowpoint ammo.
Over the next few days, I made body shots on quite a few more of those big, fat critters, with some shots as far away as 125 to 130 yards. While I did not lose a single one, I could tell I was beginning to push my luck at those distances. Based on my experience, I'd say the little cartridge begins to run short on steam at about 100 yards for body shots on game the size of a fox squirrel.
One of the beautiful things about shooting the .17 HM2 is its accuracy in a good rifle along with its flat trajectory allow the hunter to consistently make head shots on small game at distances deemed impractical for the .22 LR. This can extend its effective range on game of that size beyond 100 yards. With solid hits to the body, the .17 HM2 kills California ground squirrels--a varmint that is considerably smaller than fox squirrels--dead in their tracks out to 130 yards, perhaps a bit farther. Longer shots become iffy as the velocity of that tiny V-Max bullet drops off to the point where it begins to lose its ability to expand effectively.
The vital areas of animals such as squirrels and rabbits are quite small, so in order for a rifle/load combination to be entirely suitable for collecting them for the pot, it should be capable of shooting bullets inside an inch at whatever range game is usually taken. If you bump off most of your small game no farther away than 25 yards, then the rifle you use should deliver 1-inch accuracy at that range.
Having spent quite a bit of time in the field with several rifles that are capable of squeezing the most accuracy possible from the .17 HM2, I have become convinced of its ability to cleanly take small game out to 125 yards, as long as there are no breezes to blow that tiny bullet astray. You can duplicate its accuracy with .22 LR match ammunition, such as Eley Tenex and Remington/Eley Match EPS. Regardless of how that type of ammo is zeroed, it does not shoot flat enough for consistent hits at unknown distances once the range begins to exceed 50 yards.
You can come close to duplicating .17 HM2 trajectory with hypervelocity loadings of the .22 LR, but the accuracy of those loads in the most accurate of rifles usually restricts their practical use on small game to about 75 yards. Long ago, manufacturers discovered that for the best possible accuracy with .22 LR match ammo, velocity has to be held between 1000 and 1100 fps, and the greater the velocity increase beyond that point, the more accuracy suffers.
Its jacketed bullet makes the .17 HM2 immune to that idiosyncrasy, not to mention the fact that an accurate jacketed bullet is more easily mass-produced on high-production machinery than an accurate lead bullet. When it comes to delivering the entire package--accuracy, trajectory, energy, and the ability to buck wind--the .17 HM2 outguns any .22 LR load presently available.
So what level of accuracy should you expect from the .17 HM2? It will vary a bit from lot to lot from the same manufacturer, but when the more accurate lots are fired in a match-grade barrel, they will average 0.25 to 0.38 inch at 50 yards and 0.50 to 0.75 inch at 100 yards. It is not unusual to see individual groups fired with the .17 HM2 run considerably smaller. The smallest 100-yard group I have fired with one of my personal rifles was with Remington ammo, and it measured 0.26 inch.
When discussing the pros and cons of the .17 HM2, I must not overlook the safety factor. Whereas the bullet of the .22 LR has a tendency to hang onto most of its original weight and ricochet off into the wild blue yonder, the bullet of the .17 HM2 disintegrates into extremely small pieces upon impact so long as the range does not greatly exceed 125 yards.
During one of my test sessions, I filled 2-liter plastic bottles with water, aligned them three deep at 100 yards, and shot them with Hornady's .17 HM2 loading and the CCI .22 LR Stinger load. The .17-caliber bullet went to pieces inside the first bottle with only a single small jacket fragment making its way through the near side of the second bottle and coming to rest inside it. The 32-grain bullet of the Stinger completely penetrated all three water-filled bottles and disappeared into the dirt backstop.
As I see it, the .17 HM2 has only two things going against it. One is the fact that it heats up a barrel much quicker than .22 LR ammo. This only becomes important when you are defending your position from stampeding flickertails.
The other knock against it is cost. The least expensive .22 LR high-velocity ammunition I could find locally was Federal American Eagle at $1.20 per 50-round box, although I have seen it for less than a buck a box in discount stores. Moving on up to top-of-the-line loadings, such as Federal Game Shok, Winchester Power-Point, and CCI Mini-Mag, we arrive at $1.80 to $2.05 per box, while CCI Stinger ammo runs around $3.60 per box (those prices are bound to zoom upwards with the alarming increase in the cost of lead). In comparison, CCI and Hornady .17 HM2 ammo I priced in several stores ran from $5.70 to $6 per box, while Eley wore a $7.20 price tag.
All things considered, I believe our newest .17 will see the most use as a serious small-game cartridge, whereas the .22 LR in its many forms will still rule over casual paper punching and other recreational shooting. That is okay by me since it was never meant to replace the .22 LR anyhow. Rather, it was designed to fill performance slots not filled by its parent cartridge, and it does an outstanding job of that. No battery is complete without rifles chambered for the .17 HM2 and the .22 LR.