Compared: .338 RCM and
By Chuck Hawks
The .350 Remington Magnum was the first short magnum cartridge designed for rifles with .308 Winchester length actions. It is a true medium bore cartridge, throws a .358" bullet, and is suitable for hunting large and heavy game around the world. The .338 RCM is the latest (at this writing) short magnum, also designed for rifles with .308 Winchester length actions. It is a very powerful hunting cartridge that might reasonably be used on all CXP3 game. Because both the .350 and .338 are medium bore short magnums intended primarily for hunting CXP3 game, comparison is probably inevitable. No doubt, Remington fans will line up behind the .350, while Ruger fans will support the .338. The real purpose of this review is not to pick a "winner," but to point out the similarities and differences between the two cartridges.
The .338 RCM
The .338 Ruger Compact Magnum (RCM) is based on the .300 WSM short magnum case and is available only in Ruger brand rifles at the time this article was written. The .338 RCM is based on a shortened and necked down version of the .375 Ruger Magnum case. This is a beltless magnum with a .532" rim and base diameter. It has a little more powder capacity than the belted .350 Rem. Mag. and a bit less capacity than the rebated rim .300 WSM, although all share the same .532" rim diameter. The maximum COL is 2.840" and the .338 RCM uses standard .338" diameter bullets.
Hornady, the only ammo company that loads for the .338 RCM, is offering two factory loads. These use a 200 grain bullet at a muzzle velocity (MV) of 2950 fps and a 225 grain bullet at 2775 fps. These ballistics are taken from a standard SAAMI 24" test barrel. From a 20" test barrel, Hornady claims MV's of 2850 fps and 2710 fps, respectively. Hornady does not offer a 250 grain bullet, the weight that made the .338 Winchester Magnum's reputation on dangerous game, because the length of the heavy bullet takes up too much room inside the short case.
Reloaders in the U.S. have an excellent selection of .338" bullets. The usual bullet weights chosen for hunting the various species of CXP2 and CXP3 big game include 200 and 220-225 grains, with 225 grains being the most popular bullet for large game. However, reloaders will not be able to duplicate the factory load velocities. The Hornady factory loads use special, non-canister powders not available to reloaders.
Like any .338 Magnum cartridge, the .338 RCM kicks hard. The cartridge's inherently heavy recoil is amplified by the fact that the Ruger M77 Compact Magnum rifles offered in .338 RCM weigh only 6.75 pounds and have 20" barrels. Besides the ballistic penalty due to the short barrel, the muzzle blast and kick make this a truly vicious combination from the shooter's standpoint!
.350 Remington Magnum
The .350 Remington Magnum, first introduced in 1965, is based on a shortened version of the standard 7mm Remington belted magnum case. Case length is 2.17" and the maximum cartridge overall length is 2.8". The original Remington factory loads included a 200 grain bullet at a muzzle velocity (MV) of 2710 fps and a 250 grain bullet at a MV of 2410 fps in a 20" test barrel. These loads were discontinued and the current Remington factory load drives a 200 grain Core-Lokt PSP bullet at a MV of 2775 fps from a 22" test barrel. Stars & Stripes offers Production Ammo factory loads using 200 grain and 225 grain Barnes TSX bullets in .350 Rem. Mag. at MV's of 2892 fps and 2713 fps respectively. Stars & Stripes offers factory loads using 225 grain and 250 grain Nosler Partition bullets in their Custom Ammo line.
Reloaders have access to bullet weights of 150, 180, 200, 220-225 and 250 grains and virtually all reloading manuals include the .350 Mag. The factory load velocities are attainable with maximum reloads in rifles with 22" barrels. Bullets around 200 grains have traditionally been the most popular in .35 caliber cartridges, as they seem to have adequate killing power and kick less than the heavier bullets.
Remington currently offers the .350 Mag. in their Model Seven line and Sturm Ruger has recently offered the .350 to their Model 77 Mk-II Standard (blue/walnut) and Sporter (stainless/laminate) rifles. Used examples of the Remington Model 600M and 660 carbines, the original home of the .350 Mag. cartridge, as well as the recently discontinued Model 673, are sought after and command high prices on the used market in places like Alaska where heavy game is common.
In order to evaluate these two medium bore cartridges we will compare them in terms of velocity, energy, trajectory, bullet sectional density, bullet frontal area, killing power and recoil. Since both cartridges are factory loaded with bullets weighing 200 and 225 grains, we will compare those bullet weights.
The representative loads for the .338 RCM will be the Hornady Custom factory loads using a 200 and 225 grain SST bullets with Hornady's published ballistics for rifles with 20" barrels (Ruger M77 Hawkeye Compact Magnum). The Hornady SST is an ultra-streamlined bullet with a pointed plastic tip and a boat-tail base. The ballistic coefficients (BC) of SST bullets are among the highest of all commonly available hunting bullets.
The representative loads for the .350 Rem. Mag. will be the Stars & Stripes Production Ammo using the 200 and 225 grain Barnes TSX bullets fired from rifles with 22" barrels (Ruger M77 Mk. II and Remington Model 673). The .358" TSX bullets are hollow point spitzers with a flat base, considerably inferior to the SST design in ballistic coefficient, but they offer very deep penetration in large game.
Velocity matters because velocity is the most important factor in calculating kinetic energy and it contributes to a flatter trajectory. Here are the published velocity figures (in feet per second) for our selected factory loads:
Clearly the .338 WSM is the higher velocity cartridge downrange, although the two cartridges are similar in MV. This is entirely due to the superior BC (and thus slower rate of velocity loss) of the Hornady SST bullets used in .338 RCM factory loads.
In the case of a hunting rifle bullet, kinetic energy powers penetration and bullet expansion, very important factors in killing power. Velocity is the most important factor in calculating kinetic energy (bullet weight is the less important factor) and the .338's velocity advantage naturally translates to an energy advantage. Here are the kinetic energy figures (in foot pounds) for our selected loads:
Although the .350 has a slight advantage at the muzzle, note how the disparity in energy increases as the range increases. This is again because of the superior BC of the .338 SST bullets. Load the .350 with equally sleek bullets (such as the Swift Scirocco) and the downrange energy would equalize. In terms of remaining bullet energy, around 1200-1500 ft. lbs. at bullet impact is considered adequate for 500 pound game such as elk.
Here are the trajectory figures in inches for our selected loads at 100, 200 and 300 yards. For comparison purposes, all are assumed to be fired from scoped rifles zeroed at 200 yards, the basic parameters used by Hornady in developing their ballistics tables.
Not surprisingly, due to the superior BC of its SST bullets, the .338 RCM shoots a little flatter than the .350 Mag. The difference with both bullet weights amounts to 0.2" at 100 yards and about an inch at 300 yards, which is surprisingly little and unlikely to be critical, considering the size of the vital heart/lung area of big game animals and the fact that the maximum point blank range of both cartridges is well under 300 yards. In terms of trajectory, both calibers are in the same class.
The sectional density (SD) of bullets is calculated by dividing a bullet's weight (in pounds) by the square of its diameter (in inches). Sectional density is important because, given bullets of identical design at identical velocity, the bullet with the greatest SD will penetrate the deepest. The deeper the wound channel (of any given diameter) in a game animal the more tissue is destroyed and the greater the killing power. However, in this case the design of the bullets is definitely not the same. The SST is known for rapid, large diameter expansion, while the TSX expands more slowly and to a smaller frontal area. Indeed, the TSX bullet is famous deep penetration. Here are the SD numbers for our selected bullets:
Because the .350 bullets are fatter, their SD is lower for any given bullet weight. The 200 grain .338" bullet is almost equal in SD to the 225 grain .358" bullet. SD's of .223 are excellent for CXP2 game and SD's of .250 and better are satisfactory for CXP3 game. In the case of the .350 Mag., the 200 grain bullet has also accounted for plenty of CXP3 game, so it is hard to generalize. The big .35 caliber bullet is a ruthless killer.
Because of the differences in bullet performance, I doubt that either caliber has much real world advantage in either the length or diameter of the permanent wound cavity with bullets of comparable weight. The difference in bullet design and performance probably nullifies the .338's inherent advantage in SD.
Bullet cross-sectional area
Bullet cross-sectional area is important because the wider the wound cavity (of any given depth), the more tissue is destroyed and the greater the killing power. The actual diameter of a .338 bullet is .338" and the actual diameter of a .350 Mag. bullet is .358". Here are the bullet cross-sectional areas for our two calibers:
Clearly a .350 Mag. bullet will, other things (such as bullet expansion) being equal, always punch a larger diameter hole than a .338 RCM bullet. The .350's advantage in cross-sectional area is a constant, regardless of velocity, energy, SD, or bullet weight. However, in the case of our selected factory loaded bullets, the Hornady SST is known for greater expansion than the Barnes TSX, just as the TSX is noted for deeper penetration than the SST. Because of the differences in bullet performance, I doubt that either caliber has much real world advantage in either the length or diameter of the permanent wound cavity. The difference in bullet design and performance probably nullifies the.350 Magnums inherent advantage in cross-sectional area.
Killing power is very hard to quantify due to the mass of variables, not the least of which are the game animal's state of mind when shot and the effect of bullet expansion on the wound channel. These facts notwithstanding, many authorities have tried to devise formulas to estimate the killing power of rifle bullets.
In my opinion, one of the best attempts is the "Optimum Game Weight Formula" (OGW) devised by Edward A. Matunas. This at least attempts to take into consideration the various quantifiable factors affecting killing power and is not intended to prove some special theory. Most of all, OGW seem to have a positive correlation with actual results in the field.
The results of Optimum Game Weight are expressed in terms of the range and live animal weight for which a given cartridge is optimum. (There is an extensive OGW table on the Tables, Charts and Lists Page of Guns and Shooting Online.) Here are some OGW results (in yards) for our cartridges:
Once again, the .350 wins at the muzzle, but the superior BC of the Hornady SST bullet, because it retains energy better downrange, accounts for most of the difference (on paper) between these two cartridges as the range increases. On the other hand, the Barnes TSX has established a reputation as a superior killing bullet on large game in the field. We know from experience that both of these calibers, with bullets of proper construction and weight, are adequate for hunting elk, moose, grizzly bear and similar size big game. Keep in mind that outsize 1000 pound or dangerous animals are seldom shot at ranges exceeding 150 yards.
The .338 RCM's advantages in lightweight, highly portable rifles and increased case capacity are purchased at a price, and that price is heavy recoil. Neither cartridge is a soft shooter, but the .338 is definitely the worst offender.
Any magnum rifle should weigh no less than 8.5 pounds, including a scope, which is about what the Remington Model 673 and Ruger M77 Mk. II .350 Mag. rifles actually weigh. For calculating .350 Mag. recoil, we will use a rifle weight of 8.5 pounds.
Unfortunately, Ruger's 6.75 pound M77 Hawkeye Compact Magnum rifles will only reach about 7.75 pounds with a scope, which puts the .338 RCM at a definite disadvantage. For calculating .338 RCM recoil we will use a figure of 7.75 pounds.
The reality is than anyone can shoot more accurately with a rifle that kicks less and bullet placement remains, by far, the most important factor in killing power. Those are important facts to keep in mind when choosing a powerful rifle. Here are some recoil energy (in foot-pounds) and velocity (in feet/second) for comparison:
What this table illustrates is that the .350 Rem. Mag. kicks hard compared to a typical small bore all-around rifle, but not as violently as the .338 RCM. The majority of shooters are happy with a rifle that kicks with less than 15 ft. lbs. of energy and 20 ft. lbs. is about the maximum tolerable recoil. Both of these cartridges and all four loads are far above that amount of recoil.
The .350 Mag. shooting a 200 grain bullet is way over the average shooter's comfort level and the .338 RCM is a couple of foot-pounds worse. The .338's recoil velocity is also higher. Excessive recoil and muzzle blast were blamed for the lack of popularity of the Remington Model 600M and 660 carbines in .350 Mag. back in the late 1960's, and the .338 in Ruger's Compact Magnum carbine is even worse. Frankly, that does not bode well for the long term success of the .338 RCM cartridge.
We've had a lot of fun with numbers, but just how good are these two cartridges at killing (or stopping, if necessary) large and/or dangerous animals? The answer is that both cartridges should be very good when using heavy bullets, as long as the hunter can arrange to get the bullet into a vital spot. The .338's advantage in sectional density with 200-225 grain bullets is largely negated by the .350's advantage in bullet frontal area and the differences in terminal performance. With controlled expansion bullets, both calibers will shoot from side to side through the chest of a bull elk.
The .350's biggest advantage is that it normally kicks less than the .338 due to the availability of heavier rifles. The .350 would be a better choice for anyone who has misgivings about the recoil of the .338 RCM. In reality, the choice may be decided by what model of rifle the buyer prefers or can find, since rifles in both calibers are scarce.
Reloaders will likely prefer the .350 Rem. Mag. because reloading data is widespread and it can handle the heavy 250 grain .35 caliber bullets. These provide an SD comparable to the 225 grain .338 bullet with greater frontal area and bullet weight, the best of all possible worlds. Maximum reloads can typically drive a 250 grain bullet at about 2500 fps (as do Stars & Stripes Custom factory loads using the 250 grain Nosler Partition bullet) and this would probably be the best choice for hunting very large or dangerous game with either caliber.
Copyright 2009, 2012 by Chuck Hawks. All rights reserved.