Compared: .338 Winchester Magnum, .338-06 A-Square and .338 Ruger Compact Magnum
By Gary Zinn
The .338 Winchester Magnum has dominated the .338 caliber slot ever since its introduction in 1958. Many articles have been written extolling the virtues of the cartridge, so it would be redundant for me to repeat it all here.
The .338 Winchester Magnum set a performance level for the caliber at a point that most subsequently developed .338 cartridges have struggled to better. Five cartridges that are currently viable do this, but I am not very interested in these, for reasons I explain in, The .338 Win. Mag. Versus the .338 Super Magnums (.330 Dakota, .340 Wby. Mag., .338 RUM, .338 Lapua Mag. and .338-378 Wby. Mag.).
I am more interested in comparing the performance of the .338 Winchester Magnum with the only two SAMMI-standardized cartridges that nip at its heels, the .338-06 A-Square and the .338 Ruger Compact Magnum (RCM). A thorough examination of ballistic data indicates that these two cartridges are capable of performance that closely approaches the .338 Win. Mag., while being somewhat milder to shoot.
Factory load comparisons
Whether looking at a particular cartridge on its own merits or comparing different cartridges, the logical place to start is with the ballistic data for available factory loaded (commercial) ammunition. There is a wealth of commercial ammo made for the .338 Win. Mag., but the availability of .338-06 and .338 RCM cartridges is severely limited. I found only one line of ammo for each of these: Hornady Superformance for the .338 RCM and Nosler Custom for the .338-06. (When A-Square standardized the .338-06, Weatherby briefly offered .338-06 factory loads, but no longer does.)
This simplified my comparison problem. I used the Hornady Superformance line of .338 Win. Mag. cartridges as my baseline and matched those with .338 RCM and .338-06 factory cartridges with equivalent weight bullets. Hornady loads neither .338 Win. Mag. nor .338 RCM cartridges with a 250-grain bullet, so I used the Nosler Custom 250 grain load for the .338 Win. Mag., to compare with the .338-06 250-grain load.
Here are the comparisons, starting with muzzle velocity for each load. The total spread between highest and lowest MV for each bullet weight set is also noted. Muzzle velocity values are as stated by the manufacturers.
Muzzle velocity, 180 - 185 grain bullets
130 fps total spread; .338 Win. Mag. MV 4.4% > .338-06 MV
Muzzle velocity, 200 grain bullets
230 fps total spread; .338 Win. Mag. MV 8.2% > .338-06
Muzzle velocity, 225 grain bullets
240 fps total spread; .338 Win. Mag. MV 9.2% > .338-06
Muzzle velocity, 250 grain bullets
125 fps total spread; .338 Win. Mag. MV 5.1% > .338-06 (Note: there is no 250-grain factory load for the .338 RCM.)
There is nothing surprising about these data. The .338 Win. Mag. has the highest muzzle velocity in each bullet weight, with the .338 RCM running second and the .338-06 the slowest velocities. However, the velocity spreads are not startling; all three cartridges drive the various weight bullets fast.
The ballistic data for the .338-06 and .338 WM cartridges are for 24 inch barrels (typical of rifles in these calibers), while the .338 RCM data are for a 20 inch barrel. This is because the Hornady/Ruger team that developed the .338 RCM purposely set out to create a cartridge for a short action, short barreled rifles that would duplicate .338 Win. Mag. ballistics and Ruger M77 rifles in .338 RCM are supplied with 20 inch barrels. The data shows they fell slightly shy of the latter goal.
After muzzle velocity, one can generate reams of data on external ballistics, but to me there are only two variables that are important. These are maximum point blank range (MPBR) and retained energy at MPBR.
Here are these data for the factory cartridges listed above. MPBR is calculated for a bullet trajectory of +/- 3 inches from line of sight, using www.ShootersCalculator.com. Retained energy is calculated at the 25 yard increment nearest to the MPBR range of each load, using the ballistics calculator at www.hornady.com. The total spread between highest and lowest MPBR and retained energy for each bullet weight set is also noted.
MPBR and retained energy, 180 - 185 grain bullets
15 yard MPBR total spread; .338 Win. Mag. MPBR 5.3% > .338-06
316 ft.lbs. energy total spread; .338 Win. Mag. energy 15.0% > .338-06
MPBR and retained energy, 200 grain bullets
24 yard MPBR total spread; .338 Win. Mag. MPBR 8.8% > .338-06
425 ft.lbs. energy total spread; .338 WM energy 19.4% > .338-06
MPBR and retained energy, 225 grain bullets
21 yard MPBR total spread; .338 Win. Mag. MPBR 8.0% > .338-06
349 ft.lbs. energy total spread; .338 Win. Mag. energy 14.2% > .338-06
MPBR and retained energy, 250 grain bullets
12 yard MPBR total spread; .338 Win. Mag. MPBR 4.9% > .338-06
262 ft.lbs. energy total spread; .338 Win. Mag. energy 11.3% > .338-06
Even with a stringent MPBR parameter of +/- 3 inches, the .338 Win. Mag. has impressive reach; about 300 yards with the 185-grain Hornady GMX bullet and 260 yards with the 250-grain Nosler Partition. The .338 RCM and .338-06 loads have MPBRs that are not substantially shorter.
Despite the current long range shooting craze, I feel that all of these loads have more than adequate MPBRs for practical and ethical hunting purposes. To me, long range shooting at the rifle range and long range hunting shots in the field are two entirely different things, but that is a subject for another article.
Several factors combine to determine the terminal performance of a bullet on a live target. However, energy on target is the variable that says the most about the effectiveness of similar cartridge/bullet loads.
Every one of these loads carries over a ton of retained energy at maximum point blank range. There is really not much more that needs to be said. A few hundred ft.lbs. difference in bullet energy is trivial, given the amounts of energy these cartridges carry down range. For instance, an elk hit in the vitals at 250 yards with a 250 grain bullet from a .338-06 will be just as dead as with an identical hit with the equivalent .338 Win. Mag. load.
Anyone who wants a high performance .338-caliber rifle, but who does not hand load, should buy a .338 Winchester Magnum and be happy. There is a wide range of .338 Win. Mag. commercial ammo available from all of the major manufacturers, so reloading the cartridge is not imperative. Conversely, one must be prepared to reload .338-06 or .338 RCM to get the most out of these cartridges and to be assured of a reliable ammo supply. Here is a summary of the ballistics of the top performance, maximum reloads for the three cartridges, starting with muzzle velocity.
Muzzle velocity, 185 grain Hornady GMX bullets
200 fps total spread; .338 Win. Mag. MV 7.0% > .338 RCM
Muzzle velocity, 200 grain Hornady SST bullets
150 fps total spread; .338 Win. Mag. MV 5.3% > .338 RCM
Muzzle velocity, 225 grain Hornady SST bullets
150 fps total spread; .338 Win. Mag. MV 5.7% > .338 RCM
Muzzle velocity, 250 grain Hornady Interlock SP bullets
200 fps total spread; .338 Win. Mag. MV 8.0% > .338 RCM
All data is from the Hornady Handbook of Cartridge Reloading, 9th Edition. The data for the .338 Win. Mag. are for a 24 inch barrel, while the .338-06 and .338 RCM data are for 23-1/2 and 20 inch barrels, respectively. Whenever more that one powder recipe gave the same highest muzzle velocity with a given bullet weight, I listed the powder that used the smallest charge weight.
These loads for the .338 Win. Mag. give muzzle velocities only 30 to 40 fps slower than the factory loads for 185, 200 and 225 grain bullets, while the 250 grain load is 100 fps faster than its factory load counterpart. Meanwhile, the .338-06 loads listed are 50 to 125 fps faster than the corresponding factory loads.
What might seem odd is that the .338 RCM reloads are 100 fps or more slower than factory loads. However, part of the .338 RCM development package was a specially formulated powder, designed to wring the greatest possible performance out of the .338 RCM case and the 20 inch barreled Ruger M77 rifle for which the round was designed. This powder is not available to reloaders and the available powders do not yield velocities that match those generated by the non-canister factory load powder.
Comments in the Hornady reloading manual suggest that most of this lost velocity could be regained if the load recipes for the .338 RCM were used with a 24 inch barrel rifle. However, no commercial rifle manufacturer currently offers a 24 inch barreled .338 RCM. Accordingly, the idea that .338 RCM reloads can be made to match factory ammo performance by shooting them in a longer barrel is currently irrelevant.
Here are the MPBR and retained energy at MPBR data for the hand loads listed above.
MPBR and retained energy, 185 grain Hornady GMX bullets
19 yards MPBR total spread; .338 Win. Mag. MPBR 6.8% > .338 RCM
146 ft.lbs. energy total spread; .338 Win. Mag. energy 6.6% > .338 RCM
MPBR and retained energy, 200 grain Hornady SST bullets
15 yards MPBR total spread; .338 Win. Mag. MPBR 5.4% > .338 RCM
180 ft.lbs. energy total spread; .338 Win. Mag. energy 7.6% > .338 RCM
MPBR and retained energy, 225 grain Hornady SST bullets
14 yards MPBR total spread; .338 Win. Mag. MPBR 5.3% > .338 RCM
306 ft.lbs. energy total spread; .338 Win. Mag. energy 12.7% > .338 RCM
MPBR and retained energy, 250 grain Hornady Interlock SP bullets
18 yards MPBR total spread; .338 Win. Mag. MPBR 7.3% > .338 RCM
306 ft.lbs. energy total spread; .338 Win. Mag. energy 13.4% > .338 RCM
The most significant thing about this data is how closely the downrange performance of the .338-06 approaches the .338 Win. Mag. Across the four bullet weights, the maximum differences are nine yards in MPBR and 116 ft.lbs. in bullet energy at MPBR. Maximum .338 Win. Mag. and .338-06 loads are very similar in downrange performance.
The .338 RCM reloads have 14 to 19 yards shorter MPBRs and about 150 to 300 ft.lbs. less downrange energy that the corresponding .338 Win. Mag. loads. Whether these are truly important differences is a matter of opinion. My opinion is they are not.
I give this much attention to reloads for these cartridges, because of the severely limited availability of .338-06 and .338 RCM factory ammo. This implies that anyone who wants to get the most from either of these cartridges should be prepared to handload them. Here are some additional thoughts on loading the .338-06 and .338 RCM.
Suitable powders and bullets are widely available for either cartridge, so the only real considerations that might separate them are the availability of cases, the amount of powder used and the relative cost of reloaded vs. factory ammo.
The only available brass for the .338 RCM is made by Hornady, so one must have new or previously fired Hornady brass in .338 RCM to reload. Currently (mid-2015) Hornady .338 RCM brass retails for about $1.10 each.
The selection of .338-06 brass is somewhat better, with Norma, Nosler and Weatherby brand brass on the market. Depending on brand and vendor, this brass retails for about $1.70 to $2.50 each. (I do not know why these suppliers are so proud of this particular brass.) However, the .338-06 is simply the .30-06 case necked up to accept .338 diameter bullets, so .338-06 dimension brass can be easily formed by resizing .30-06 cases with a .338-06 die. With new .30-06 brass retailing for 50 cents to $1.00 each, this is an attractive alternative.
The .338-06 and .338 RCM do not burn as much powder as does the .338 Win. Mag. Among the reloads listed above, the .338 RCM uses 10 to 23 percent less powder per charge and the .338-06 14 to 23 percent less.
Finally, if one is going to do volume shooting of any of these cartridges, reloading will quickly become cost effective relative to buying factory ammo. .338 RCM and .338 Win. Mag. factory loads currently retail for $40 or more for 20 cartridges, while .338-06 ammo is almost twice as expensive as the magnums. A set of reloading dies will cost about the same as a single 20-round box of factory ammo.
Using the .338 RCM as an example, the approximate cost of dies ($40) and 100 pieces of new brass ($110) adds up to about $150 in initial hardware cost for someone who already has a basic reloading outfit. Enough powder, primers and bullets to load 100 cartridges would cost about $70, making the total cost of loading the first 100 rounds approximately $220. The cost of 100 rounds of comparable factory ammo would be about $200.
With dies and brass in hand, the additional cost of loading the next 100 rounds will drop to about $70. Thus, the cost of a set of dies and supply of brass is amortized early in the second loading of the first batch of brass.
Sound and fury (muzzle blast and recoil)
I have had one experience with shooting a rifle in this power class. A while back, a fellow member of my shooting club asked me to help him sight in a new scope he had just mounted on his .338 Win. Mag. rifle. I spotted hits for him while he adjusted the scope and my reward was an opportunity to shoot some 100 and 200 yard target groups, to confirm those he had shot after zeroing the rifle.
The recoil of the .338 Win. Mag. commanded my attention, but it was not overwhelming. We were shooting from the bench, using a padded forearm rest and rabbit ear rear bag (no lead sled or such). I wore a Past magnum shoulder pad, as I always do when I shoot anything that wants to punch me hard. We were shooting 200 grain factory loads.
I crunched the recoil energy numbers for the handloads listed above. Doing so required inputting, into a recoil calculator program, the various bullet and powder charge weights, muzzle velocities and a firearm weight. I assumed a field equipped rifle weight of 9.0 pounds for all three cartridges. I based this on the 8.0 pound catalog weight of the Ruger Guide Gun in .338 RCM caliber and added a pound for scope and mounts, etc.
Recoil energy values ranged from 24.2 ft.lbs. for the .338 RCM 185 grain bullet load, to 38.4 ft.lbs. for the .338 Win. Mag. 250 grain bullet load. Recoil energy of the four .338 WM loads averaged 33.6 ft.lbs., the .338-06 loads 27.6 ft.lbs. and the .338 RCM loads 27.4 ft.lbs.
These recoil levels are greater than those found with most smaller caliber rifles and loads, but I have dealt with worse. The hardest kicking gun which I have shot extensively is my Remington Model 870 12 gauge magnum turkey shotgun. The three inch shells that this gun shoots best generate about 45 ft.lbs. of recoil energy.
I have never really been aware of this recoil when shooting at turkeys, but I certainly notice it when I do range work with the gun. For instance, once I got a new choke tube and wanted to evaluate the patterns it threw against those produced by the tube I had been using. By the time I had fired five patterning shots with each tube, my shoulder told me it was time to stop.
The point is, I know what heavy recoil feels like and in my limited experience with the .338 Win. Mag., I would say its recoil is not too bad. Given that the numbers say the .338-06 and .338 RCM generate recoil levels somewhat below those of the .338 Win. Mag., I see no problem with tolerating the recoil of those cartridges. Your results, of course, may vary.
Further, all three cartridges can be loaded down to reduce recoil, while still maintaining solid ballistic performance. To illustrate, I did the math for a 200 grain Hornady SST bullet loaded to a muzzle velocity of 2500 fps. This bullet, at this velocity, would give a MPBR of 248 yards with retained energy of 1864 ft.lbs.
The Hornady reloading handbook shows this can be done with a powder charge of 46.2 grains of Viht N-135 in the .338-06, 49.3 grains of Varget in the .338 RCM and 52.5 grains of Viht N-150 in the .338 Win. Mag. In nine pound rifles, these loads would generate 18.8, 19.6 and 20.5 ft.lbs. of recoil energy respectively. (For context, an eight pound .30-06 rifle firing a 165 grain bullet at 2800 fps would generate right at 20 ft.lbs. of recoil energy.)
Turning to muzzle blast, I can give only qualitative speculations. Generally, the blast generated by .338-06 and .338 RCM rifles should be at least marginally less than that of the .338 Win. Mag. (for the same bullet weight loads at or near maximum muzzle velocity). The reason I assert this is that the .338 WM uses more powder per equivalent load than do the other two cartridges.
This assumes that comparable loads among the three cartridges are shot through equal length barrels. The ringer here is the Ruger .338 RCM Guide Gun comes with a 20 inch barrel, while .338 Win. Mag. rifles typically sport 24 or 26 inch barrels. If I were to have a .338-06 rifle built (more on this below), I would specify a 23 or 24 inch barrel. Generally, a shorter barreled generates more muzzle blast than a longer barrel, other things being equal. I would expect the Ruger .338 RCM to be louder in a 20 inch barrel than the other two calibers in 23-24 inch barrels.
The Ruger Guide Gun comes with a muzzle brake. My experience with muzzle brakes is that, acoustically, they turn a boom into a scream that is hard to adequately muffle with any hearing protection device. The Guide Gun muzzle brake can be switched out with either a provided muzzle weight or thread protector, which is the way I would go. I hate muzzle brakes and want nothing to do with a gun that has one. Many professional outfitters will not allow hunters to use rifles equipped with muzzle brakes, something to keep in mind if you are shopping for a powerful big game rifle.
My solution to dealing with the muzzle blast of any powerful gun is to wear double ear protection (plugs under electronic muffs) at the range. For almost two decades I have also used electronic muffs when hunting with a rifle or shotgun. I am trying to protect what hearing acuity I have left.
Availability of rifles
Virtually every rifle manufacturer who makes an action suitable for standard length magnum cartridges offer rifles in .338 Win. Mag., which is the most popular of all medium bore cartridges and a top 10 best selling cartridge. Accordingly, the buyer has a wide choice of well-built and appointed bolt rifles in, roughly, the $800 - $1000 price range (2015 prices). Economy rifles in .338 Win. Mag. are available (you will get what you pay for) and deluxe production, semi-custom, or custom built rifles are widely available at higher prices. In addition to bolt actions, the Benelli R1 and Browning BAR autoloading rifles are offered in .338 Win. Mag., as are some single shot rifles.
Turning to the .338 RCM, there is only one game in town. The Ruger Guide Gun is a stoutly built version of the Model 77 Hawkeye rifle, featuring a 20 inch barreled action of stainless steel and a laminated wood stock that comes with butt pad spacers that can be used to adjust its length of pull. The M77 Guide Gun is currently available in seven calibers, including the short action .338 RCM. The 2015 MSRP is $1240.
To my knowledge, no commercial rifle maker currently offers a .338-06 rifle, although Weatherby did when A-Square was still offering factory ammunition. (A-Square was the company that had the .338-06 SAMMI standardized, but the firm went out of business in 2012.)
If you want a new .338-06 today, there are basically three ways to get one. First, you can have a barrel job done on a .30-06; i.e., have the barrel of a .30-06 rifle rebored to .338-06, or a new barrel made and fitted onto a .30-06 action. Second, you can order a semi-custom rifle from Shaw Precision Guns. Finally, you can have a true custom rifle built.
Regarding the second option, Shaw Precision Guns (a.k.a., E.R. Shaw Barrels) will build their Mk. VII rifle to your specifications. They offer a wide range of barrel options and walnut, laminated hardwood or synthetic stocks. The Shaw rifles are built on Savage 10/110 bolt actions and come with the excellent Savage AccuTrigger. A Mk. VII rifle will run from $775 to $1250, depending on the options selected. You can specify options for your rifle on their website (www.ershawbarrels.com) and immediately submit the specs for a price quote. (Guns and Shooting Online has ordered a Shaw rifle in .338 Federal caliber for a review.)
I used the "build your rifle" function on the E.R. Shaw website to spec a .338-06 rifle in matte stainless steel, with a 23 inch sporter weight barrel and laminated stock. I got a price quote via e-mail the same day for just over $900, including shipping to my FFL. The only caveat in the Shaw deal is that they are not into instant gratification. The e-mail I got from them noted that, "The average turnaround time on a Mk. VII rifle build is in the 12 month area."
I knew going into this project that the .338 Winchester Magnum dominates the .338 cartridge niche and after doing the research I now have a much better understanding of why. The cartridge is a perfect storm in the bore size, for it shoots 180 to 250 grain bullets far and hard. Further, it does so without obscene levels of recoil, muzzle blast and shooting expense.
The ballistics data clearly show that the .338-06 A-Square and .338 RCM cannot quite match the .338 Win. Mag. in performance (muzzle velocity, MBPR and down range bullet energy). However, I am convinced that these numerical differences are insignificant in practical terms. A few yards difference in MPBR and a couple hundred ft.lbs. difference in terminal energy are of very little consequence in the field, with cartridges as powerful as these.
Here are my thoughts on the merits of these two almost .338 Win. Mag. performance cartridges. Regarding the .338 RCM, I believe its best feature is that the folks at Hornady and Ruger found a way to get near .338 Win. Mag. performance from a .308 Winchester length cartridge. I am not sold on the 20 inch barrel length and I feel the cartridge (especially for the reloader) would benefit from being offered in a rifle with a normal, magnum length, 24 inch barrel. Even a 22 inch barrel, the length Remington chose for their .350 Mag. in the short action Model Seven rifle, would be an improvement. (See Compared: .338 RCM and .350 Remington Magnum.)
I do not expect Ruger to unbend and offer a longer barreled rifle, but perhaps the cartridge will gain enough market traction that other rifle manufacturers will eventually do so. A Browning BAR ShortTrac autoloading rifle in .338 RCM, with a 23 inch barrel, would be quite interesting.
On its merits, the .338-06 should have gained market viability after it was SAMMI standardized (circa 1996), but this has not happened. When the A-Square Company closed in 2012, it effectively orphaned the cartridge. However, the .338-06 continues to intrigue me, because it is capable of delivering near magnum level performance from a standard capacity case, without a lot of fuss. (See Compared: North American Medium Bore Rifle Cartridges for more information.) Perhaps that is the problem: the cartridge is not sexy enough to become a fad. They should have called it the .338-06 Light Magnum for marketing purposes.
If I get wild and crazy and decide that I must own a .338 caliber rifle, it will be a .338-06. I still have the price quote for that Shaw Mk. VII rifle.
Copyright 2015 by Gary Zinn and/or chuckhawks.com. All rights reserved.