The Rook Rifle Project Part 1: Concept & Foundation

A few weeks ago I came across an opportunity to divest myself from my disposable income in my favorite fashion. That, of course, means that I was going to buy a gun. However, I wanted to do more than simply buy a gun. Being what has been termed a rifle loony, I would only be satisfied by building the perfect niche gun. For this iteration, I had settled on building a modern version of the classic Rook Rifle.

Concept. For those unfamiliar, a *Rook Rifle was a British arm of moderate caliber intended for shooting small game and vermin. The archetypical Rook Rifle was a single shot (often a Martini design, but not necessarily) with excellent handling characteristics, a mild report, and a weight that was a joy to carry afield.  Historic Rook Rifles range from the proletarian, to the jaw-droppingly beautiful. When I originally made the decision to build a Rook Rifle, I thought that I was quite clever and probably the only person in modern times to pursue such a notion. I was unequivocally wrong. Furthermore, one could also claim that the British Rook Rifle has now morphed into the broader category of the Walking Varmint Rifle.

* Writer’s Note: a rook is the British equivalent of a crow or raven. If you are of Scots ancestry, you would call it a corbie.

Foundation. As a lover of single-shots, I was beholden to the Rook Rifle tradition. Single-shots provide a shorter overall length, enormous strength, excellent handling characteristics, and a variety of chambering options. In order to simplify the build process (and to satisfy a long-held lust) I opted for one of the Thompson-Center (T/C) break-open designs. This means one of two receivers: the Contender or Encore. The Contender is a more petite frame, with better trigger potential, but can only handle moderate pressure cartridges. The Encore is larger, with a trigger that is less easily improved, but can handle higher-pressure rounds. Truth be told, either frame would suffice for this project because of typically low-pressure rounds utilized. However, I happened to find an Encore Pro Hunter frame at an excellent price on Gunbroker and purchased it for economic purposes. In total, this saved me about $120 off the cost of the Contender frame, which could be applied to the barrel. The factory furniture that I received with the Pro Hunter frame was black injection-molded. The forend has rubber finger groove inlays for traction and the buttstock has internal recoil dampeners built in and a very soft recoil pad. For the purposes of this build the recoil countermeasures were moot. Generally speaking, the furniture is utilitarian and not particularly aesthetically pleasing. It is weather-proof, but will likely be replaced with walnut sometime in the future.

Thompson Center Pro Hunter Frame

Cartridge and Loads. Original Rook Rifle cartridges are all practically obsolete. I suspect that one could not find factory brass for a single one. Luckily, there is a plethora of suitable cartridges existent today (some still very old). In pondering cartridges for this project, I decided that my priorities would be (1) suitable small-game performance up to 150 yards, (2) availability of reloading dies and components, (3) cost of reloading dies and components, (4) mildness of report and recoil, and finally (5) pedigree / intangible coolness factor.

The short list that I developed is included below. Included for each cartridge is an example of a factory loading, cost per box (source Midway USA), and advertised external ballistics.

.17 Hornet

Load: Hornady Superformance, 20 gr. VMAX

Advertised Velocity: 3,650 FPS

Cost: $18.79 (per 25, $0.75 per round)

.17 Remington Fireball

Load: Remington Premier Varmint, 20 gr. Accutip

Advertised Velocity: 4,000 FPS

Cost: $29.99 (per 20, $1.50 per round)

.22 Hornet

Load: Hornady Varmint Express, 35 gr. VMAX

Advertised Velocity: 3,100 FPS

Cost: $18.29 (per 25,  $0.73 per round)

.25-20 Winchester

Load: Winchester Super-X, 86 gr. SP

Advertised Velocity: 1,460 FPS

Cost: $65.99 (per 50, $1.32 per round)

.25-35 Winchester

Load: Winchester Super-X, 117 gr. SP

Advertised Velocity: 2,230 FPS

Cost: $48.99 (per 20, $2.45 per round)

.32 H&R / .327 Federal Magnum

Load: Federal American Eagle, 85 gr. JSP

Advertised Velocity: 1,400 FPS

Cost: $26.49 (per 50, $0.53 per round)

.38 SPL / .357 Remington Magnum / .357 Max

Load: Remington UMC, 125 gr. JSP

Advertised Velocity: 1,450 FPS

Cost: $29.49 (per 50, $0.59 per round)

.44 SPL / .44 Remington Magnum

Load: Remington UMC, 180 gr. JSP

Advertised Velocity: 1,610 FPS

Cost: $41.99 (per 50, $0.84 per round)

Ultimately, I had to consider the availability of factory ammunition as well. My final decision was a derivative of the .22 Hornet cartridge, the .22 K-Hornet. This cartridge was developed by Lysle Kilbourn in 1940. Factory .22 Hornet loads can be fired in the .22 K-Hornet with a slight loss in velocity. However, this process effectively fireforms the brass, which simplifies the reloading process. Like other improved cartridges, the .22 K-Hornet has a characteristic steep shoulder and increases the powder capacity when compared to the parent case. This translates into increased velocity potential. For instance, the 9^th Edition of the Hornady Handbook of Cartridge Reloading shows the highest velocity charge listed for the Hornet pushing a 35 gr. VMAX as 3,100 FPS. With the K-Hornet, the same velocity can be attained with the 40 gr. VMAX. However, my intent in selecting the K-Hornet was not to push the velocity envelope, but rather to increase the longevity of brass life. The parent Hornet case is notorious for stretching the neck of the cartridge, which requires frequent trimming and frequent brass replacement. The 40° shoulder and decreased body taper of the K-Hornet derivative increases brass life and minimizes required trimming.

Hornady (Left) and PPU (Right) .22 Hornet Factory Loads, Skinner Rear Sight

As previously mentioned, this cartridge selection was not based on attaining maximum velocity. As such, moderate loads will likely be used. Typically, cartridges in the .22 K-Hornet class are loaded with highly frangible bullets suitable for high velocity and explosive fragmentation on non-edible species. For shooting prairie dogs in open country this is perfect as it immediately terminates the animal upon impact and reduces the possibility of ricochet. However, I am a consummate small game eater and prefer intact carcasses for proper butchering. This necessitates heavy-for-caliber bullets, thicker bullet jackets, and more moderate velocities. Although I have not had the opportunity to reload for the .22 K-Hornet yet, I have already purchased dies and a few of the Hornady bullet #2245, a 50 gr. soft point varmint bullet with a thicker jacket. A similar bullet (#2240) is of identical weight but is constructed with a much thinner jacket to facilitate fragmentation.  According to the Hornady manual, this bullet can be pushed to 2,700 FPS in the K-Hornet. However, I believe that I will keep it between 2,200-2,500 FPS (depending on what the rifle favors). I suspect that this will minimize meat damage and will be a boon while hunting game at the end of the medium-size spectrum (turkey, bobcat, javelina, and coyotes).

Factory Ammunition, Reloading Components, and Dies are Widely Available

Bullet #2245 has a G1 ballistic coefficient of 0.214, which is relatively poor. Assuming a 25 yard zero, a sight height of 0.5” above the center of the bore, and a muzzle velocity of 2,300 FPS we receive the following trajectories via JBM Ballistics Calculator:

Calculated Table
Range	Drop	Drop	Windage	Windage	Velocity	Mach	Energy	Time	Lead	Lead
(yd)	(in)	(MOA)	(in)	(MOA)	(ft/s)	(none)	(ft•lbs)	(s)	(in)	(MOA)
0	-0.5	***	0.0	***	2300.0	2.060	587.2	0.000	0.0	***
25	0.0	0.0	0.1	0.5	2202.7	1.973	538.6	0.033	5.9	22.4
50	0.1	0.1	0.5	1.0	2107.8	1.888	493.1	0.068	12.0	22.9
75	-0.4	-0.5	1.2	1.5	2015.2	1.805	450.8	0.105	18.4	23.4
100	-1.4	-1.3	2.1	2.0	1925.1	1.724	411.4	0.143	25.1	24.0
125	-2.9	-2.2	3.4	2.6	1837.5	1.646	374.8	0.182	32.1	24.5
150	-5.1	-3.3	5.0	3.2	1752.7	1.570	341.0	0.224	39.5	25.1
175	-8.0	-4.4	7.0	3.8	1670.9	1.497	309.9	0.268	47.2	25.7
200	-11.7	-5.6	9.4	4.5	1592.2	1.426	281.4	0.314	55.3	26.4

This configuration works perfectly for a 150 yard small game cartridge.

Barrel. You might think that few rifles are chambered in .22 K-Hornet and you would be correct. However, there are a number of custom barrel makers for T/C Contender and Encore that do offer this chambering. One of the benefits of these rifles is that their barrels are easily swapped, thereby changing calibers. Barrel makers such as Bulberry, MGM, and SSK Industries all offer the .22 K-Hornet cartridge.

I opted to go with SSK Industries for no particular reason. To be honest, Bulberry seemed to be overly variable in the barrel prices based on caliber and I wasn’t certain that MGM would be able to install a ramped front sight on their barrel (they are, but more on that later). SSK Industries, owned by JD Jones, has a long history of Contender and Encore work.  In addition, JD has been on the forefront of cartridge development. His work includes creation of the .300 Whisper (the predecessor to the .300 AAC Blackout) and the JDJ series of cartridges. Notably, the .375 JDJ has long been held to be THE big game hunting cartridge for the Contender platform. After exchanging email with JD I decided that he would be my barrel-maker and I provided him with the following specifications:

Chamber: .22 K-Hornet

Profile: Same as factory Pro Hunter (.810”)

Length: 16”

Additions: Ramped front sight with 1/16” bead

Rate of Twist: 1 in 12”

These specifications are in keeping with the Rook Rifle concept. When applied to the Encore frame, this barrel would yield a relatively light, handy carbine with iron sights. You’ll notice that I did not ask JD to install a rear sight. That’s because I already had designs on the excellent Skinner aperture rear sight for T/C rifles. This sight, which is mounted on the factory-spaced scope mount holes, maximizes the sight radius for a short-barreled carbine. In addition, the aperture design is flexible; additional apertures of differing diameters can be ordered. By varying the aperture diameter one can let in more or less light as appropriate for the application.

Skinner Rear Aperture Sight

Photo from http://www.skinnersights.com/thompson_center_19.html

Intended Quarry. The sad truth of the American hunting scene is that the good old days of knocking on a farmer’s door and getting permission to big game hunt are coming to an end. Land access is the #1 challenge that hunters face. Although hunter numbers in recent years have declined, a deluge of next-generation hunters (the so-called “Hipster Hunters”) will likely exacerbate access issues. However, hunting needs all the advocates that it can get. These days, if you want big game access you either have to buy land outright, lease land, or hunt public land. Worse yet, public land is fraught with its own challenges. Belligerent or dangerous hunters on public land is often a sad reality. What is worse, each Congressional session threatens to sell-off the already limited public hunting land. What’s a man to do? Eat squirrel.

No, seriously! Small game opportunities still exist where big game hunting opportunities do not. Landowners don’t often expect to be paid for small game access, so prime real estate is often within reach. Despite being often overlooked as table fare, small game is also delicious. Preparations for small game are widely available and the general difficulty is low. Regardless of where you are located, prime small game hunting is likely only a short drive away. My experience hunting in Oklahoma and Kansas has been that squirrel, rabbit, raccoon, predator, and wild turkey hunting provides hours of entertainment without the pressures associated with whitetail deer hunting.

Double-Battered, Fried Squirrel is only Missing White Gravy

One of the reasons that I selected the .22 K-Hornet over the .17 Hornet (another .22 Hornet stepchild) is that the variety of .224” diameter projectiles offers much more flexibility. The lightest projectiles (such as the Hornady 35 gr VMAX, Barnes 30 gr. Varmint Grenade, and Calhoon 30 gr. Double HP) are perfect for non-edible rodent and vermin control. Yet, the option exists to shoot up to 55 gr. projectiles (perhaps heavier) that could be used for small deer-sized game in a pinch. I do not and will not advocate hunting deer with .22 caliber rifles, but shorter premium bullets (read as: non-tipped, non-homogenous) make it a possibility in the .22 K-Hornet. As I have previously noted, mid-range bullets such as the 50 gr. Hornady SP split the difference—you have the weight for larger quarry and the slightly controlled expansion does not render small game inedible.

Conclusion. At this time I am still waiting on my SSK Industries barrel, but I expect it to arrive within the week. That’s why this is Rook Rifle Project Part 1! In the next article I hope to offer up some eye-candy photos and to give my initial impressions on not only the rifle’s accuracy, but how well it fills the Rook Rifle niche.