Sunday GunDay: .204 Ruger Cooper M21 Montana Varminter
We are well into spring 2026. That means folks will be getting ready for varmint safaris into prairie dog country. Todays’ story may help you choose a cartridge for your next varmint rifle. This Sunday we feature a Cooper chambered for the .204 Ruger — an impressive cartridge with way more speed that a .223 Rem, plus a flatter trajectory.
For many years, Ken Lunde journeyed to South Dakota to visit with his father, and do a little varmint hunting. This article features Ken’s Cooper Model 21 Montana Varminter chambered in .204 Ruger. During past varminting holidays in South Dakota, Ken had a chance to try the speedy .204 against his “old reliable” .223. He came to favor the .204 for its accuracy, flat trajectory, and superior performance in the wind. Ken told us: “I love my .223, but the .204 has the edge for Dog-Town duty.”
The Cooper Montana Varminter in .204 Ruger
Story and photos by Ken Lunde
I’ve been a big fan of Cooper Arms rifles ever since my dad introduced them to me a few years ago. I prefer Cooper Arms rifles over others because they perform as they should out-of-the-box, and have outstanding workmanship and beauty. You get form and function. You don’t need to choose one over the other. For the price one pays, Cooper Arms rifles are a great bargain. I mount a quality scope, usually a higher-end Leupold with a 40mm objective, go through barrel break-in, and they always perform extraordinarily well. I should state that all of my rifle shooting is geared towards hunting. In other words, any shooting I do on paper is treated as preparation for using the same rifle for hunting, whether it’s for varmints such as prairie dogs, or for larger game.
Photos Copyright © Ken Lunde, All Rights Reserved
Cooper Varmint Rifles–Components and Variations
The featured rifle is a Cooper Arms M21 Montana Varminter (aka “MTV”) chambered in .204 Ruger. It has a 24″ varmint-taper stainless steel barrel with a 1 in 12-inch twist. This twist rate seems to be typical of .204 Ruger barrels from other manufacturers. The stock is AA+ grade Claro Walnut, and has the varmint fore-end, “Buick” vents, and steel grip cap that are standard on the Montana Varminter configuration. Among Cooper’s three wood-stocked varmint rifle configurations — Varminter, Montana Varminter, and Varmint Extreme — I prefer the Montana Varminter as it seems to be the best balance of value versus features. Plus, I like the “Buick” vents. They’re very pleasing, at least to my eyes. Maybe that’s why I own seven of them, in M21 and M22 actions, and in a variety of calibers. [Editor: Ken’s father has a near-identical .204 Ruger Cooper, with consecutive serial number.]
For this rifle, I decided to mount a Leupold VX-III 6.5-20×40 LR scope with the Varmint Hunter reticle. The rifle came with Leupold STD bases in Matte finish, and I used Leupold 30mm STD rings in Medium height and Matte finish. I took the time to align the bottom rings on the bases, and properly lapped them. Other than mounting the scope, no custom work was done, because none was necessary. The trigger is superb out-of-the-box, which is typical of Cooper rifles.
Load Development and Accuracy
I first tried factory ammo, loaded with Hornady 32gr and 40gr V-Max. The 32gr load shot the best — five-shot groups were slightly larger than a half-inch at 100 yards. My dad heard that Alliant Reloder 10X was a good powder for this cartridge, and he worked up a load using the Sierra 32gr BlitzKing bullet. He found that 26.5 grains was the right amount for his rifle. Considering that my rifle was probably made on the same day, having a consecutive serial number, I decided to try my Dad’s load, along with a half-grain up and down: 26, 26.5, and 27 grains of powder. I, too, found that my rifle prefers 26.5 grains of RL 10X. With this load, I could shoot consistent quarter-inch, five-shot groups at 100 yards. Cartridge OAL is 2.353″, or 1.990″ measured from the ogive.
I am using Winchester brass, Federal 205M primers, Alliant Reloder 10X powder, and Sierra 32gr BlitzKing bullets. I use Forster dies, and load with a Forster Co-Axial single-stage press. Here are two typical targets. As you can see, this .204 can shoot.
 |
 |
WARNING: Current lots of Reloder 10X powder may be somewhat different. 26.5 grains of RL 10X may be TOO HOT for your rifle and 32gr bullets. Seating depth, throat length, and COAL will affect pressures dramatically. START LOW at 24.5 grains and work up.
Cartridge Smack-Down — .204 Ruger vs. .223 Remington
Ken made these comments when he first tested his .204 Ruger vs. his trusty (and very accurate) .223 Remington: “I brought along two rifles. The first was my ‘proven’ varmint rifle, the one chambered in .223 Rem. It has stunning wood, and clearly escaped the factory with AAA grade Claro Walnut. That rifle also shoots consistent five-shot, quarter-inch groups at 100 yards. For the .223, my preferred load uses Winchester brass, Federal 205M primers, Hornady 40gr V-Max bullets (non-moly), and 26.2gr of Vihtavuori N133 powder.
I found that I very much enjoyed shooting the .204 Ruger rifle, which explains why I used only the .204 Ruger during the second trip, although I also brought along the .223. Why did I favor the .204? Well, those little 32gr bullets really zing out of the barrel, with a very flat trajectory, like a .22-250. And, to my surprise, they buck the wind very well, perhaps even better than .223. While I am no ballistics expert, I think that this may be due to its high velocity, clearly over 4,000 fps.
Related to the flat-shooting characteristics of the .204 Ruger cartridge, I found that I was able to depend on my Leupold’s Varmint Hunter reticle for both bullet drop and wind compensation. It was a very pleasing experience. For determining ranges in the field, I used a new set of optics for this trip, Leica’s new Geovid 8×42 BRF range finder.
| Comparative Ballistics: .204 Ruger vs. .223 Remington vs. 22-250 |
| Cartridge | Bullet | BC | Powder | Max Load | Muzzle Vel | 400yd Drop | 400yd 10mph Wind |
| .204 Ruger | 32gr V-Max | .210 | Benchmark | 28.0 | 4047 fps | 25.50″ | 17.88″ |
| .204 Ruger | 40gr V-Max | .275 | H4895 | 27.7 | 3741 fps | 26.93″ | 14.10″ |
| .223 Rem | 40gr Nosler BT | .221 | Benchmark | 27.3 | 3666 fps | 30.67″ | 19.02″ |
| .223 Rem | 50gr Nosler BT | .238 | BL-C(2) | 28.0 | 3428 fps | 34.21″ | 19.01″ |
| 22-250 | 40gr Nosler BT | .221 | H4895 | 37.0 | 4060 fps | 24.73″ | 16.67″ |
Load data from Hodgdon.com, for 24″ barrel. 2.250″ COAL .204s, Fed 205s. 2.210″ COAL for .223 Rem, Winch SR. 2.350″ COAL for 22-250, Winch LR. Always start 10% low and work up. Calculated at 1000′ altitude, 80° F.
This 2022 third-party video records the performance of .204 Ruger Hornady factory ammunition with both 32gr and 40gr V-Max bullets.
Editor: When this story was originally written, Ken Lunde made two summer trips to South Dakota to hunt prairie dogs with his father. Here is his account of those summer-time adventures. I drove to South Dakota twice [that year]. For the first trip, I brought two Coopers, both M21 MTVs, in .223 and .204 Ruger. My .223 Cooper was already proven during previous trips to South Dakota. I fired a total of 300 rounds, 200 from the .204 Ruger and 100 from the .223. I found the .204 Ruger to be flatter-shooting than .223, and it also seemed to buck the wind better, even with the light 32gr bullets. For the second trip, I ended up shooting 301 rounds, all from the .204 Ruger rifle. I had discovered the importance of accuracy when hunting prairie dogs — and the .204 Ruger had exceptional accuracy. There are many variables with which to contend while shooting: wind speed, wind direction, variable distance to target, bullet drop, steadiness, and the accuracy of the load in the rifle. I find that the more of these variables I can control or compensate for, the greater the success.
The best part of these trips is spending quality time with my dad, doing something that both of enjoy: shooting and hunting. I grew up in Wisconsin, and my parents moved to South Dakota in December of 2004. South Dakota, and sometimes Wyoming, have come to be our preferred hunting states, because they’re superb hunting destinations. It is great that my parents have decided to settle in one of those states. In fact, the drive from California is not bad. It takes a little over one day. I also brought my teenage son along. He enjoyed the chance to go fishin’ with Grand-Dad, and one day “teen-angler” managed to catch us six fine trout.
My father has a rather vast collection of Cooper Arms rifles, so I naturally invited Dan Cooper to check them out. A couple of them turned out to be special. One turned out to be the very first .22-250 rifle that Cooper Arms built. It is a Model 22 Varmint Extreme with ebony fore-end tip. Another is an Model 21 Classic with Schnabel fore-end, and according to Dan, less than 30 such rifles were ever crafted. It’s in the rack picture at left. Two of Dad’s rimfires are also very early Coopers, with two-digit serial numbers. They were made before Cooper started using the magazine insert supplied by Anschütz. And check out the middle rifle in the rack. It’s a Dakota Arms Model 97 Deluxe Hunter that I bought for Dad. He hand-picked the amazing wood blank, and it turned into an outstanding rifle stock. You can see how it stands out in the photo. Interestingly, the day before our dinner, I used Dad’s M21 with the Schnabel stock, chambered in .222, to hunt prairie dogs in the 9,000 acres of public hunting land bordering the eastern side of my Dad’s 56-acre “recreational” property, situated just north of Hot Springs, SD. Here’s a photo. Yes, I’d say this is a great place to hunt and “get away from it all”.
|
I estimate I bagged about 250 prairie dogs during each trip, meaning about 500 in total for this season. There were misses, of course, but those are generally 400 yards and beyond, when wind becomes too much of a factor, or shooter error. And, for each trip, I managed to get two or three “doubles,” which is lingo that means that a single bullet results in two dead prairie dogs. Prairie dogs tend to congregate, and when they do, “doubles” become possible, and “triples” are not out of the question. One of these “doubles” was clearly visible through my scope.
My first trip to South Dakota, at the end of June, offered a unique oppor-tunity, since First Stop Guns was having a show that coincided with my time in the area. Dan Cooper, founder and owner of Cooper Arms, was present at the show. My dad and I decided to host a small dinner at my parents’ new home, and we invited Dan Cooper and others. I brought tenderloin steaks from California for this. In addition to Dan Cooper, Mark and Steve Blote of First Stop Guns, along with Paulette Kok of Dakota Arms, attended the dinner. It was a pleasure and honor to be in their company. They’re all very personable.
