The .17 frenzy

With its case splits apparently a thing of the past, Hornady ammo is an accurate and reliable choice

With the runaway success of the .17 HMR, and the newly launched 17 Hornet hitting the shelves soon, Nick Latus looks at the lost .17 Mach 2 rimfire

Although many of you will be oblivious to its presence, the .17 Mach 2 has been around for some time. It was launched in 2004, and the first commercially available Mach 2 rifle to really be in the public eye was the Sako Quad, which included the Mach 2 in its team of four barrels. The uptake was slow, and most owners merely had the calibre in the cupboard as a result of the four-barrel package deal. So the question was never really answered: What is the .17 Mach 2 really for and how does it perform? I hope to shed some light on that.

Whereas the massively successful HMR was based on a necked-down version of the 22 WMR, the Mach 2 makes use of the CCI stinger case of the age-old .22LR. With a 20-degree shoulder and the same 17-grain ballistic tip bullet as the HMR, the Mach 2 followed the same design logic as the other .17 calibre. Using the latest technology in powder development, and the lightweight, incredibly accurate .17 V-Max bullet, the new calibre looked to far surpass the capabilities of its .22 counterpart. With much higher velocities, the .17s benefit from flatter trajectories and greater killing power.

Trajectory is a sensible place to start. Even compared to hyper-velocity .22 ammo, the HMR’s little brother is some 600fps faster, averaging 2,100fps. Pushing out the light 17-grain bullet, the .17’s corresponding trajectory is also markedly flatter. With a 100-yard zero you are only looking at a 0.7in rise (HMR is about 0.2in), whereas the corresponding 31-grain Hyper Velocity ammo in .22 would shoot 2.4in high at 60 yards. So it wins that contest hands down.

Compared with the HMR, it does lag just over 400fps behind in MV, with the gap staying consistent at 200 yards. Also, the HMR at 200 yards delivers just 16ft/lb less than the Mach 2 at 100 yards. What is more interesting, though, is that compared to 36-grain High Velocity .22 ammo at 100 yards, the Mach 2 only just edges ahead on energy, with 8ft/lb more.

The usual suspects: .17 HMR, .22LR and .17 Mach 2 line up alongside each other

The accuracy of the HMR has always been inherently good, although some rifles can be a bit picky with brand. There isn’t a lot of choice when it comes to Mach 2 ammo, as the only manufacturer readily available in the UK comes from the creator. That’s no bad thing, as Hornady HMR ammo is a top choice, and having used a large amount of their centrefire ammunition in recent months, I have no doubts as to its quality.

Despite my test rifle being a base model CZ, with the usual jittery creep in the trigger and stock touching the barrel down one side, the accuracy was very good. Grouping at 60 yards was constantly 0.4in, which was on par with any HMR ammo I had fired. Moving out to 100 yards the Mach 2 didn’t quite replicate its big brother’s performance, shooting into just over 1.5in. Having said that, my current .17 HMR has had the stock modified and a trigger re-work, which could easily account for this difference.

Beyond this range I did find that groups dropped off quicker than the larger-cased .17. This makes sense, as testing the .17 HMR at increasingly extended ranges has indicated that the accuracy wanes at reduced velocities. Given that the Mach 2 starts some 450fps slower, these effects will be seen sooner.

So compared to the humble .22 it seems to do just about everything better. Well, on paper at least. There are downsides, of course. The first is that there is no subsonic version, so it will never be as quiet as a .22 – although it should be noted that the crack from the Mach 2 is noticeably more subdued than the HMR. The ammo cost is also higher at around £9 a box, owing to the expensive heads and high tolerances required in the manufacturing process.

In testing there were two notable issues, which are worth bringing to light. The first is one that will be known to HMR owners, where the primer goes off without igniting the powder. This annoyingly results in the bullet jamming up the barrel. It can manifest itself in another form as well, where there is a noticeable delay between the two ignitions. Both of these I encountered with the Mach 2 in one batch of ammo.

The second issue has also occurred with HMR ammo, where the cases split down the neck. According to the manufacturers this was down to the annealing process, resulting in weak brass at this point. Although I know it does occur, I have to say I have not experienced this with the HMR. On the other hand, this problem was apparent with some of the Mach 2 ammo.

Closer inspection of these cases showed that some of them had developed a hairline crack before firing, resulting in a full case split upon ignition. Understandably, velocity and accuracy were affected when this occurred, and explained the odd spike when passing rounds over the chronograph.

On discovering this I went back to Edgar Brothers to share my concerns, and as to be expected from such an established and respected company, they were immediately on the case, feeding the information back to Hornady. Thanks to the close working relationship between the two companies, an investigation was promptly launched with batch numbers sent over to the USA.

I have to say I was impressed with the turnaround, which took little over 24 hours. I am informed that the issue with splitting cases occurs because the necks cannot be annealed, as with centrefire cartridges. The result of this was some cases splitting upon firing, while a smaller number showed visual cracks before chambering.

On the problem of misfires, it seems that it is actually a related issue, where the hairline case cracks allow moisture absorption, and in turn cause a misfire. Hornady acknowledged the issue but reliably informed me that this has now been resolved and all new lots will no longer experience these problems. As the shooter it is obviously frustrating, especially when these malfunctions occur in the field, but it is comforting to know how important the consumer feedback is to both the distributor and manufacturer.

Putting all this to one side, I was still very eager to see how the little wonder performed in the field. After all, the HMR has proven to be a runaway success. Over a couple of weeks the Mach 2 joined me on rabbiting forays both during the day and at night, where I fired just over 50 rounds in anger. It was obvious at the extended ranges that it was the not the bunny destroyer the HMR was, but certainly seemed to have greater immediate effect than a standard .22LR, augmented of course by the fact that shots out to 100 yards were infinitely less challenging owing to the much flatter trajectory.

The Mach 2's carcase damage falls in between the .22LR and .17 HMR

The little .17 is sold as suitable out to 100 yards on small varmints, and I would have to agree with that. The poor sectional density of the 17-grain bullet is compensated for by extreme speed, but the drop-off after 100 yards is such that it rapidly becomes less effective. I would liken it to the HMR beyond 200 yards. You will still kill with it, but with less repeatable consistency.

An observation displaying this occurred when I was undertaking carcase comparisons. The picture below shows three rabbits shot between 60 and 70 yards through the front of the chest. The substantial fragmentation of the HMR has left a two pence-sized exit wound, with a significant amount of shot meat around the area. A section of the lung is clearly visible. Internally very little of the lungs were left intact despite the bullet only passing through the front edge.

The .22 subsonic caused far less carcase damage, with a clean hole in and out. Far less bruising is visible, and apart from the immediate area of the lungs where the bullet passed through, there is very little extended damage.

Lastly, the Mach 2 exhibited an amount of damage that was unsurprisingly in between the two other rounds. The bullet passed slightly at an angle through the opposite shoulder, and fragmentation caused an external wound that was noticeably larger than the bullet diameter. However, on this carcase, as also observed in others, the internal damage was markedly different to the blended, congealed remains that were inevitably obvious from a shot with the HMR over the same ranges.

Examining the internals showed half of the lungs mangled and blood-shot, while the rear remained intact. I assume the reduced velocity means the level of fragmentation is curtailed. This seems to follow from the retrieval of the bullet under the skin of a number of rabbits shot just beyond the 100-yard mark. As shown in the picture, the 17-grain bullet is almost entirely intact with the exception of the plastic tip. I have never experienced this with the HMR, although often shots at the 200-yard range are not retrieved. To give some comparison, the energy delivery at 190 yards with the HMR is about the same as the Mach 2 at 100 yards.

There is no doubt that on trajectory alone the Mach 2 is superior to anything the .22LR can offer. Given that the issue with ammo reliability has now been addressed, it is also a very accurate calibre. I am still undecided as to the useful applications it has, though. I think for those who don’t own a .22LR, and have no intention of using the quiet subsonic ammo, this is a more sensible choice. On the other hand, the HMR does everything better and at longer ranges, though it has marginally more report and substantially more carcase damage. To add to this, ammo for the Mach 2 is about half the price if you can find it. I have to say I am neither here nor there, but I can’t see me replacing the HMR.

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