Magnum Rimfire Comparison: .17 HMR,
By Chuck Hawks
After reading my article "Compared: .17 HMR and .22 WMR," Guns and Shooting Online member Johnny C. Kitchens wrote to me suggesting the inclusion of the 5mm Remington Rimfire Magnum (RFM) in a magnum rimfire comparison article. Good idea!
I considered simply adding the 5mm Remington data to the existing article, which would have been a little easier from the html aspect. But ultimately I decided to use that data in a new, separate article. This piece is the result.
The .22 Winchester Magnum Rimfire (WMR), introduced in 1959, is the original magnum rimfire cartridge. It quickly became a best seller, is offered by all of the major ammo manufacturers, and has been adapted to a wide variety of rifles and handguns.
The 5mm Remington was introduced in 1970 as a higher velocity, flatter shooting alternative to the .22 WMR. Despite its excellent ballistics, it was a commercial flop. Remington rifles for the 5mm were discontinued after 1974, and the ammunition was discontinued a few years later. Today the 5mm Remington is an obsolete cartridge, as neither ammunition nor rifles are available.
Much later, in 2002, our third rimfire magnum varmint cartridge was introduced, the .17 Hornady Magnum Rimfire (HMR). Unlike the 5mm RFM, the .17 HMR was an immediate success. It is now available in pretty much the same rifles and handguns as the .22 WMR.
The .22 WMR
Winchester (Olin) designed an entirely new and larger case when they introduced their .22 Magnum. Unlike the previous .22 Long Rifle, the Magnum is based on a longer (1.052") and fatter case. And the bullet is a full .224" diameter, like modern centerfire .22 bullets. In form, the .22 WMR case remains a straight sided, rimfire type with a cartridge overall length (COL) of approximately 1.350". The maximum chamber pressure is around 25,600 psi.
The new bullet weighed 40 grains, the same as the .22 LR bullet, but it was a true jacketed bullet, available in jacketed hollow point (JHP) and full metal jacket (FMJ) forms. .22 WMR bullets are generally of flat point or round nose shape, although Remington offers a pointed AccuTip-V bullet.
The original catalog muzzle velocity (MV) from a rifle barrel was 2000 fps, or 1550 fps from a pistol barrel. The major U.S. manufacturers have since reduced the catalog velocity of the 40 grain bullet to 1910 fps (rifle) and 1480 fps (pistol).
Over the years, practically every manufacturer who loads rimfire ammunition has adopted the .22 WMR and different loads have been introduced. The original 40 grain bullet weight is still the most popular, but we now also have higher velocity loads using lighter 30-34 grain bullets from CCI, Federal, Remington, and Winchester. There are also .22 WMR loads using heavier 45-50 grain bullets at (necessarily) lower velocities.
The 5mm Remington Rimfire Magnum
The 5mm Rimfire Magnum is based on a case similar, but not identical, to a necked-down .22 Magnum case. Its case is a little bigger and it has to be stronger as it must contain 50% greater pressure, 22,000 psi Vs 33,000 psi. Bullet diameter is .2045", or .20 caliber, the same as the new .204 Ruger centerfire cartridge.
The Remington factory load drove a 38 grain Power-Lokt semi-spitzer hollow point bullet at a muzzle velocity (MV) of 2100 fps. This offered an increase of about 25 yards of practical range compared to the .22 WMR.
It was introduced in a pair of Remington bolt action rifles, the Models 591 (clip magazine) and 592 (tubular magazine). T/C chambered their Contender for the 5mm for a short time. As far as I know, those were the only firearms available in 5mm RFM. The cartridge was not picked-up by other rifle or ammunition companies. However, during the first decade of the 21st Century, Centurian brand began selling new 5mm Mag. ammunition made in Mexico in the U.S. (I was told by a Centurian representative that Guns and Shooting Online articles about the 5mm Rem. RF Mag. had helped stir interest in the cartridge.) This allows shooters who own Remington 5mm rifles to get them back into service.
In retrospect it is hard to understand why the 5mm was such a commercial flop. Its ballistics were quite appealing, as we shall see. I think that the answer is that in 1970 the market was simply not ready for a new rimfire cartridge with an "undersize" bullet. Like the .350 and 6.5mm short magnum centerfire cartridges and Electronix ammunition, the 5mm RFM was too far ahead of its time. If it had it been introduced in 2000 with much fanfare, the outcome might have been different.
The .17 HMR
The .17 HMR was introduced in 2002 and has become the most successful cartridge introduction since the .22 WMR. The initial sales of 17 HMR rifles was so strong that the demand for ammunition far outstripped supply for the first couple of years. Hornady was the first supplier of .17 HMR ammunition, but within two years CCI, Federal, and Remington all adopted the caliber.
The .17 HMR is based on the .22 WMR case necked down to accept .172" bullets. It is a bottleneck rimfire case about 1.060" long. The rim diameter remains .291". The chamber pressure and cartridge overall length are exactly the same as the .22 WMR, so any firearm that can be chambered for that cartridge can also be chambered for the .17 HMR.
The original Hornady load drove a specially designed 17 grain V-Max bullet at a MV of 2550 fps and ME of 245 ft. lbs. This is a polymer-tipped, spire point, boat-tail bullet. It is a varmint bullet, designed to fragment in small animals and disintegrate if it hits a hard surface. In 2004 Hornady introduced a less destructive 20 grain XTP bullet at a MV of 2375 fps. This bullet is advertised as a controlled expansion, deeper penetrating bullet for small game hunting.
Hornady's .17 HMR ammunition is loaded with great precision. It is intended to deliver 1 MOA or better groups at 100 yards. The other brands seem to have followed Hornady's specification in this matter. All of the .17 HMR ammunition that I have tested has proven to be very accurate.
We will compare the .17 HMR, 5mm RFM, and .22 WMR in terms of velocity, energy, trajectory, bullet frontal area, and killing power. But first we have to decide what loads to compare. Of course, that is an easy task in the case of the 5mm RFM, as only one load was ever available. So the discontinued Remington load using a 38 grain Power-Lokt JHP bullet at a MV of 2100 fps is it.
One of the newer high performance .22 WMR varmint loads is Remington's Premier Gold Box ammo. This load uses a 33 grain AccuTip-V bullet at a MV of 2000 fps (load #PR22M1). That will be our .22 WMR load of choice for this comparison.
In .17 HMR the 17 grain Hornady V-Max bullet is loaded to a MV of 2550 fps in the Federal, Winchester, Hornady and Remington brands. These remain the fastest, flattest shooting and most popular .17 HMR loads. The bullet in the Remington Premier Gold Box version is called an AccuTip-V, but is actually the V-MAX with a gold tip. This is the load (#PR17HM1) that will represent the .17 HMR.
So the three loads I propose to compare are the 17 grain Remington AccuTip-V at 2550 fps in .17 HMR, the 33 grain Remington AccuTip-V bullet at 2000 fps in .22 WMR, and the Remington 38 grain Power-Lokt bullet at 2100 fps in 5mm RFM. Ballistics for all three calibers will be taken primarily from Remington ammunition catalogs, supplemented by Hornady ballistic information for the .17 HMR where necessary.
Velocity matters because it flattens trajectory, making hitting at long range easier. Here are the velocity numbers in feet-per-second for various ranges from the muzzle to 200 yards (N/A = not available):
From these numbers it is obvious that the .17 HMR is the velocity king. This bodes well for its trajectory and long range energy figures. And at 100 yards the 5mm RFM has a 110 fps advantage over the .22 WMR.
Velocity is an important factor in calculating kinetic energy, but so is bullet weight. We have already seen that the .17 HMR is by far the fastest cartridge, but the .22 WMR and 5mm RFM shoot much heavier bullets. Energy is important because it powers bullet expansion and penetration and is a major factor in killing power.
Here is the energy of our comparison loads, in foot-pounds at the muzzle, 50 yards, 100 yards, 150 yards, and 200 yards (when available):
Here we see a different story. The 5mm RFM easily exceeds the energy of the other two cartridges at all ranges. And the .17 HMR, despite its high velocity, carries the least energy. I would guess that the 33 grain .22 WMR bullet retains an energy advantage over the .17 HMR out to at least 150 yards, which is well beyond its maximum point blank range (MPBR).
High velocity has a big effect on trajectory, as does the ballistic coefficient of the bullet. (An area where plastic tipped bullets excel.) Here are factory figures based on a 100 yard zero and a line of sight 1.5" over bore (a scoped rifle):
As expected, the .17 HMR shoots flatter than the 5mm RFM or .22 WMR, which are just about equal out to 150 yards. In terms of practical maximum range the .17 HMR has at least 25 yards over either.
Bullet cross sectional area
Bullet frontal area is important because it is a factor in the diameter of the wound channel it makes. Of course, if a bullet fragments immediately after impact, its frontal area in the conventional sense ceases to exist. This is exactly what the 17 grain HMR, 5mm RFM and 30 grain WMR bullets are designed to do. Fragmentation is typical of varmint bullets in general.
Bullet frontal area is important when considering a controlled expansion or FMJ bullet intended to penetrate deeply. The frontal area of the tiny .172" bullet is only 0.0232", while the frontal area of a .204" bullet is 0.0326". The cross sectional area of a .224" bullet is 0.0394", the best of the bunch.
Assuming a proper hit in the animal's vitals, killing power is primarily determined by (but not entirely limited to) the width and depth of the wound channel. This, in turn, is influenced by bullet energy, frontal area, sectional density, and expansion characteristics. In other words, it is a complicated matter that is still not entirely understood. One thing for sure, bullet placement is the single most important factor in killing power. This is true of varmints as well as big game animals.
There have been many systems devised to compare the killing power of rifle cartridges. The best "system," in my opinion, is plenty of experience killing game. On big game animals this is rarely practical, but experienced varmint hunters have killed a sufficient number of small animals to have a pretty good idea of what works and how well.
In the case of the .22 WMR, 5mm RFM and .17 HMR, experience has shown that all three are effective on small varmints (prairie dogs, ground squirrels, sand rats and the like) beyond the cartridges' maximum point blank ranges. In other words, they will kill about as far as you can hit the target. This gives the .17 HMR the advantage on the smaller varmints, since it shoots flatter and allows lethal hits at greater range.
On large varmints such as jack rabbits (hares) and marmots (woodchucks, rock chucks and ground hogs), the greater energy and larger diameter bullets of the 5mm RFM and .22 WMR should add up to increased killing power within their MPBR. However, bear in mind that the .17 HMR out ranges the other two cartridges.
As a point of fact, the .17 HMR hits about as hard at 150 yards as the standard velocity .22 Long Rifle does at the muzzle, and we all know that the .22 LR will effectively dispatch these larger varmints at very short range.
Summary and conclusion
The .17 HMR, 5mm RFM, and .22 WMR are all useful varmint cartridges. Recoil and muzzle blast are low, particularly from a rifle. They are good cartridges for use in semi-populated areas. .17 HMR accuracy is typically exceptional, but the other two cartridges are not slouches in the accuracy department, either.
The .17 HMR has an advantage in velocity and trajectory/range. The .22 WMR has an advantage in bullet cross sectional area. The 5mm RFM has an advantage in energy at all ranges and probably in killing power on the larger varmints. It is in-between the other two cartridges in bullet cross sectional area and virtually tied with the .22 WMR in trajectory.
After researching and writing this article, not to mention having killed a reasonable number of varmints and small predators with rimfire cartridges over a period of some 40 years, I have reached some conclusions about these three cartridges.
Out to at least 100 yards, all three are deadly varmint cartridges. No varmint can live on the differences between them.
Between about 100 and 125 yards the .22 WMR and 5mm RFM probably have an advantage over the .17 HMR for the larger species of varmints. Between 125 and 150 yards, for the larger varmints, I would favor the 5mm RFM over the other two cartridges.
Stretch the range beyond 150 yards and the flatter trajectory of the .17 HMR makes it the best choice for any sort of varmint shooting, and on the smaller species of varmints it is the top choice at all ranges.
Ammunition and rifles in .22 WMR and .17 HMR are widely distributed and commonly available. Sadly, neither is available for the 5mm RFM, which makes it a non-starter for the varmint hunter seeking a new rimfire rifle. This is a shame, and Remington should seriously consider reintroducing their 5mm Rimfire Magnum, possibly with an improved AccuTip-V bullet. As this comparison shows, it is too good a cartridge to be allowed to remain obsolete.
Copyright 2006, 2012 by Chuck Hawks. All rights reserved.