300 Ruger Compact Magnum

The 300 Ruger Compact Magnum (RCM) was designed in 2006/07 and released commercially in 2008, as a joint development between Ruger and Hornady Manufacturing. It was the third cartridge to bear Bill Ruger’s name. It is based on the 375 Ruger case but shortened and necked to accept .308-inch bullets. Testing factory loads and handloads offers excellent performance, accuracy and efficiency. It should be noted that it was never designed as an ultra-long-range cartridge; rather, it was intended to meet the needs of big game hunters who wanted to carry a lighter, shorter rifle but still have the power and long-range prowess of a .30 caliber magnum.

Perhaps the best place to begin this article is in 1999 when Remington introduced the 300 Remington Ultra Magnum, boasting a beltless case (.5500 inch head diameter) loosely based on the 404 Jeffery case. It offered greater powder capacity and velocities than the 300 Weatherby Magnum and, with an overall cartridge length of 3.600 inches, required a 375 H&H Magnum length action. It featured a rebated rim and a 30-degree shoulder. Few shooters know that Remington had simultaneously developed the 300 Remington Short Action Ultra Magnum (RSAUM) based on the same case, but short enough (2.825 inches cartridge overall length [COAL]) to work in 308 Winchester length actions. However, Remington decided to introduce the long action version first and then wait a couple of years to introduce the short action version. What the marketing department did not know was that Winchester had already been working on and refining the short action 300 Jamison cartridge, but there were complications, so they scrapped that round and developed their own beltless magnum known as the 300 Winchester Short Magnum (WSM) that was introduced in 2000/2001 and was likewise designed to function in 308 length actions (with a  COAL of 2.860 inches) and more or less duplicate 300 Winchester Magnum ballistics with bullets weighing 150 to 180 grains. Although similar, it was not based on the Remington Ultra Magnum case. However, it, too, had a rebated rim, and the head measured .5550-inch and was slightly larger than the Ultra Magnum case head. The shoulder was angled at 35 degrees.

The 300 WSM became a notable success, but soon thereafter, Remington responded by introducing the 300 RSAUM in 2001. However, the WSM had a slight ballistic advantage (usually an insignificant 15 to 50 fps) and, being introduced first, became easily the most popular. However, the RSAUM was an excellent design favored by many savvy shooters, especially target shooters, but it was not a huge commercial success.

In the meantime, Ruger and Hornady teamed up to design the 375 Ruger (introduced in 2007), which was a beltless, rimless case that was not based on any other design. Rather, the head and rim diameter are the same diameter at .532 inch, as well as the case body, which is exactly the same as the belt diameter found on the 375 H&H and all other cartridges that are based on that case. In addition to smooth feeding, the case body was larger in diameter (than the belted magnum case) for increased powder capacity. It had an overall cartridge length of 3.340 inches, the same as the 30-06, and featured a 30-degree shoulder. This combination gave it a solid 150 and even 200 fps velocity advantage over the great old 375 H&H, but utilizing powder much more efficiently.

The 375 Ruger case design was shortened and then necked to .30 caliber to permit functioning in 308-length actions. The overall cartridge length was 2.840 inches, while the case length measured 2.100 inches. The shoulder remained at 30 degrees. The .532-inch outside case diameter is .023-inch smaller than the 300 WSM, which actually served to improve feeding (which is occasionally a problem with the WSM cartridges).

Interestingly, the 300 RCM case capacity is slightly less than the 300 WSM; however, all Hornady RCM factory loads offer a ballistic advantage over the WSM. The 150-grain SST bullet is listed at 3,310 fps, the 165-grain at 3,185 fps and the 180-grain at 3,040 fps. In rough numbers, this is a 10 to 70 fps velocity advantage! These figures are based on velocities from 24-inch barrels and are from the Winchester Ammunition and Hornady catalogs. However, it should be noted that in order to achieve the above ballistics, Hornady used non-canister powders that were engineered specifically for this application. Regardless, the 300 RCM might be the best of the above short magnums; however, the advantages are minor. Before moving on, it should be noted that traditional ballistics for cup and core bullets in the 300 Winchester Magnum are listed to push a 150-grain at 3,290 fps and a 180-grain at 2,960 fps from 24-inch barrels. Clearly, the RCM offers impressive ballistics and utilizes less powder!

In spite of its impressive performance, Hornady and Ruger promoted it with comparatively short barrel lengths of 20 and 22 inches. The idea was for hunters to have a compact rifle that offered notable power at normal hunting distances on all North American game and African plains game. While I am first to favor longer barrels for use on long-range stalking rifles (due to their ballistic advantages, welcomed muzzle weight for steadier shooting, and lower muzzle report), there are times in the field when a short rifle is greatly appreciated! For example, they are handy to carry in brush and timber, carry easier when riding a horse or mule, are faster handling, especially when shooting offhand, and are generally lighter weight. In addition to being housed in compact rifles, the RCM is capable of making 500-yard shots-at least if the hunter has the skills. This qualifies it as a very interesting hunting rifle and cartridge combination.

The 300 RCM also offers outstanding efficiency. The shorter powder column (aka length to diameter ratio) results in more efficient and complete powder ignition and less unburned powder granules passing through the throat for the “sandblasting” effect that causes throat erosion. And pressure curves are more predictable and easier to control. This combination results in lower extreme spreads and outstanding accuracy.  

For today’s purposes, a Ruger M77 Hawkeye All-Weather stainless with a 22-inch barrel chambered in 300 RCM was selected. A Leupold 4-12x variable with an adjustable objective was (previously) installed. The factory hammer forged barrel has proven accurate using 165-grain SST factory loads easily grouping under 1-inch for a 4-shot string, and velocity was recorded at 3,121 fps. Interestingly, the Hornady catalog lists the velocity of this load at 3,185 fps from a 24-inch barrel. However, the box lists the same velocity but from a 20-inch barrel, which is clearly in error. Incidentally, several sources list the Ruger barrel twist at 1:12 inches. However, that is incorrect. Original Ruger specifications list it with a 1:10 twist, which the test rifle measured. This will stabilize bullets from 110 to 220 grains (but we will discuss that subject more in a moment).

In addition to factory loads, Hornady offers new unprimed cases as a component for handloaders that were used to develop the accompanying Pet Loads data. Naturally, they were first prepared by sizing to true up the case mouth, checked for proper length, case mouths chamfered and the primer pockets uniformed. Cases were then primed with Federal Gold Medal 210M primers. In spite of the RCM being a magnum cartridge, standard primers offer proper ignition and low extreme spreads and are recommended by Hornady and other ballistic labs. If using a large rifle magnum primer, maximum loads must be reduced.

SAAMI lists the maximum average pressure for the PRC at 65,000 psi. Most of the accompanying data has been pressure tested and is within that limit. However, it is suggested to begin five percent below maximum charges and work up carefully to the maximum loads. Listed loads containing spherical (aka Ball) powders should not be reduced below the suggested start charges, or delayed ignition, hang-fires, or erratic pressures can occur.

There are many excellent powders for handloading the 300 RCM. For lightweight bullets, such as the 110-grain Hornady V-MAX or 125-grain Nosler Accubond, powders with a burn rate similar to IMR-4064, Hodgdon Varget and Alliant Reloder 15 are ideal choices. Both of those bullets gave impressive accuracy with select loads and are good choices for varmints, pests, etc. Moving up to 150-grain bullets, Hodgdon Superformance, H-4350, H-414, Ramshot Big Game, Hunter, Accurate 2700, A-4350, Winchester 760, IMR-4451 and Alliant Reloder 15 each gave excellent results (including velocity and accuracy). Moving up to 165-, 180-, 200- and 208-grain bullets, Alliant Reloder 17, Reloder 19, Hodgdon Superformance, Hybrid 100V, H-414, H-4350, Ramshot Hunter, Accurate A-2700, A-4064, W-760, IMR-4350, IMR-4064, IMR-4451 and IMR-4831 each proved worthy choices. (Note: Winchester W-760, Hodgdon H-414 and Accurate A-2700 are all exactly the same powder. They split the same shipment and then distribute them under different brand names. However, like any canister-grade powder, there will be differences from one lot number to the next.)

Extruded powders generally offer an accuracy edge; however, spherical powders performed extremely well in regards to low extreme spreads, accuracy and obtainable velocities. I would not hesitate to throw spherical powders from a quality powder measure, as they offer excellent metering qualities and save time during the handloading process, and then go hunting! Notable examples include Hodgdon Superformance, Ramshot Hunter, Big Game and Winchester W-760, A-2700 and H-414 powders.

The Ruger RCM (as well as other short magnums) is short enough that they tend to be best when used with bullets that typically weigh between 110 to 180 grains, as heavier bullets tend to seat deep enough that they extend into the powder capacity. This is not a handicap, as there are many outstanding premium hunting bullets that fall within that weight range, including the Nosler Ballistic Tip, Accubond, Partition, Hornady SST, ELD-X, Swift A-Frame and many others. Many whitetail deer hunters favor various 150-grain bullets, with select loads reaching 3,250 to 3,300 fps. Various 178- to 180-grain bullets were pushed from 2,850 fps to 2,900 fps, which again is a respectable performance, especially when limited to canister-grade propellants and being fired from a 22-inch barrel! In spite of seating deep to stay within the correct overall cartridge length, handloads were developed for the Hornady 200-grain ELD-X, the 200-grain Nosler Accubond and the 208-grain Hornady ELD-Match bullets. The 200-grain versions reached 2,825 to 2,875 fps and repeatedly produced sub-MOA accuracy. Again, these velocities are respectable from a short action cartridge that uses notably less powder than larger cartridges that more or less duplicate ballistics but require more powder.

Throughout extensive handload development, the 300 RCM and the Ruger Hawkeye rifle performed flawlessly. Virtually any reasonable load produced low extreme spreads and good accuracy, with many loads giving single-digit extreme spreads for a five-shot string. Most loads were capable of sub-MOA accuracy.

Trends for rifles, scopes, cartridges, and long, heavy-for-caliber bullets have been geared to extend effective range as far as possible. However, most hunters are not skilled enough to take full advantage of state-of-the-art guns and loads that offer such outstanding levels of performance. And many things can go wrong when shooting game at extreme long ranges. Personally speaking, with respect to the game, I would rather stalk closer and eliminate many long-range variables, but that is another subject. The point is that the short magnums have slipped from the limelight, but the RCM is still a very interesting hunting cartridge that is capable of taking all North American game, even at long distances.