The 264 THOR

A Puissant 6.5 Magnum

By Charles A. Benke


Handloader’   Digest, 17th Edition, 1997


            Some years back, my decades-long passion for 6.5mm cartridges led me to a king-size one, the 264 Thor.  The Thor is a strongbelted case of good capacity, basically a necked-down, sharp-shouldered 8mm Remington Magnum.  It gives impressive velocities - like 3700 fps with 100-grain bullets, up to 3500 using 120-grainers, and almost 3400 with 140s.  To say that such ballistics will handle long-range shots at pronghorns, deer, sheep, caribou, etc., seems to be belaboring the obvious.


            The Thor isn’t the first 6.5mm magnum, of course.  Back before World War II, Schuler necked down the big beltless 8x68 case to 6.5, and RWS brought it out about 1939 with 93- and 127-grain Cone Point bullets, the former, according to advertised specs, at 3950 fps and the latter at 3450.  Hirtenberger’s two best-selling factory loads contain the 105-grain Nosler Partition and the 123-grain ABC.  CIP  specs call for a twist of 1:11 inches, which makes this cartridge most usable with projectiles weighing 140 grains or less.  The 6.5x68 has slightly less powder capacity than the Thor.  I’ve had a 6.5x68 for years, and it has performed well on lots of antelope and open-country deer.


            Slightly bigger is the belted 264 Winchester Magnum.  (Measured externally, the 6.5x68mm has more powder room, but RWS and Hirtenberger brass is thicker than Winchester’s.)  Col. Charles Askins took the American load to Africa in 1959, but it was the summer of 1960  before the 264 Model 70 could be found in gun stores.  This necked-down 338 Winchester Magnum offspring suffered bad press from the start.  It continues.  The Lyman 47th Reloading Handbook (1992) says:  “Due to short barrel life few hunters would select this round over the 270 Winchester which offers similar performance.”  That’s bad press for a big belted magnum cartridge!


            For an article in Handloader  No 160, I used six 264 Winchester Magnum rifles.  Two of them would crowd 3200 fps with a carefully prepared handload featuring Winchester’s old 140-grain two-diameter Power Point bullet, so designed to keep pressure lower.  So any 6.5mm wildcat cartridge designed to compete with these two factory magnums would have to clearly exceed 3200 fps with a 140-grain bullet.


            Winchester laboriously documented their development of the 264 Winchester Magnum.  It is so well done, one suspects the copy was put together after the cartridge was introduced.  Nowhere in that copy does it mention that several experimenters were already getting good results from the 7x61 Sharpe & Hart belted case necked down to 6.5mm.  (The 7x61 S&H, incidentally, was based on an early experimental French military rimless case, with variants in 6.5mm.  The 6.5mm Sharpe & Hart experiments simply brought this case development full circle.)


            One such experimenter was Wichita Falls, Texas, gunsmith Bill Mowrey (later of blackpowder Mowrey Rifle Co. fame).  Bill necked down the 7x61 S&H and called his creation the 6.5mm Bearcat.  Bill told me that his biggest problem in the mid-1950s was trying to find slow-burning powders suitable for the cartridge.  Today, that’s not a problem.


            While mid-size 6.5mm magnums were more popular, there have existed some rally powerful 6.55 magnums.  The 6.5 Gipson Magnum, based on the scarce Holland & Holland belted case, supposedly produced 3350 fps with a 130-grain bullet.  I don’t know the barrel length but this case also was said to push a 150-grain bullet to 3116 fps with IMR-4350.


            Oklahoma City gunsmith Art Mashburn shortened the 3000 H&H case to 2.6 inches to create his 6.5 Super Mashburn, while the 6.5 Critser Express kept the case at its full 2.8 inches.


            Col. Paul Wright used the 300 Weatherby case for a cartridge named the 6.5/300 Weatherby-Wright-Hoyer Magnum, which was used for impressive 1000-yard match shooting.  The Hodgdon lab fired this cartridge at over 3400 fps with a heavy charge of H-202 powder behind a 130-grain match bullet, at 55,000 pi.  Hodgdon carried this experiment further and built a 6.5/378 Weatherby.  It was concluded that this behemoth case would not produce more than 3400 fps with bullets of 140 grains, so it was no improvement on the smaller case.


            In more recent years, experimentation with 6.5mm magnums languished.  At the 1995 SHOT Show in Las Vegas, I was greeted at the Clymer Manufacturing Co. booth by Dave Manson, a Clymer employee and Mark Pinkston, of Kailua Custom Guns in Coquille, Oregon.  Mark moved to Oregon from Hawaii where he had full production capabilities, including manufacture of his own composite stocks. These two worthies teamed up to create a 6.5mm magnum based on the full-length 8mm Remington Magnum case, and they dubbed it the “264 Thor.”  Pinkston had built several hunting rifles for the cartridge, and it had already proved successful on elk by the time I got my hands on one.


            The 264 Thor can be described graphically as the 6.5mm-8mm Remington Magnum 35-Degree Improved.  The first sizing die was so marked.  Before apoplexy sets in contemplating such a huge container pushing a 6.5mm bullet, I remind you of the recent success of the very similar 7mm Shooting Times Westerner, and the even larger 7mm ICL and 7mm Dakota.  A fired 264 Thor case holds just a tad less powder than does a fired 7mm STW case.  As I measure it with Oklahoma well water, the 264 Thor holds 93.1 grains of water to the base of the neck, my 7mm STW case holds 94.3 grains to the same spot, while a Super-X  264 Winchester Magnum case holds but 79.7.


            The rifle Mark Pinkston shipped me for evaluation is a Remington 700 with 26-inch C. P. Donneley barrel and Mark’s own PPRS muzzlebrake.  This muzzlebrake is currently being evaluated by a major U.S.  rifle manufacturer.  The stock is out of one of Mark’s old moulds from Hawaii.  Included was a set of lading dies from Dave Daveson (4-D Custom Die Co.) of C-H Tool & Die.  The rifle came with Redfield mounts and rings, and I installed a Simmons 44 Mag scope. 


            The Rifle was shipped with twenty-five fire-formed cases.  Pinkston and Manson thought the 76.5mm wildcat would need a longer neck than the 8mm Remington parent case, so they moved the shoulder back a tiny distance.  Pinkston tells me the cases I received from him were formed by scrunching  the parent case in a 300 Winchesster Magnum die, a 7mm Remington Magnum Die, followed by a 264 Thor full-length die, then fire-formed using 25 to 28 grains of Bullseye powder with no bullet.  It obviously worked.  I grabbed several 300 Weatherby Magnum brass and sized them in the 264  Thor seater die firs, then full-length sized them in the sizer die, and fire-formed them with 28 grains of Bullseye.  I noticed no significant difference between his formed cases and mine.


            The 264 Thor, like the parent 8mm Remington Magnum brass, is 2.84 inches in length.  A loaded round of 3.66 inches functions through this Remington Model 700.  A rifle’s magazine dictates maximum loaded length, but 3.66 inches is probably typical.  Unless or until factory STW brass becomes more widely available, 8mm Remington Magnum and 300 Weatherby Magnum brass will continue to be the parent cases for this cartridge.  The 7mm STW brass converts to 264 Thor with one pass through the sizer die.


            The shooting began.  Since the 264 Winchester Magnum’s 3200 fps with 140-grain bullet was my beginning threshold, I created a table for the very slow powders that would achieve that initial velocity from the 264 Thor.  (See Table l.)


            This table belies its true usefulness.  I do not consider any powder burning faster than H-1000 to be suited for full-power loads in this cartridge.  For instance, 6/IMR-4831 indeed yields 33200 fps, but 68 grains of the same powder will lock the bolt.  Since a carefully prepared handload in a select 264 Winchester Magnum rifle will produce the same velocity, there’s no much merit in using the “faster” ultra-slow powders in this cartridge.


            Appropriate powders for the 264 Thor are those designed for the 50 BMG and the various 20mm and 25mm rounds.  Several companies market these ultra-slow powders through gun periodicals and retailers, but reloading information is scarce.  I’ll describe some of my components.


            VV 24N41 if VihtaVuori Oy’s extruded powder for the 50 BMG.  The granules are smaller and shorter than those of IMR-5010.  VihtaVuori considers this a canister powder; the canister weighs 8 pounds.  Its burning rate (in the Thor is between H-1000 and IMR-5010.  VV 24N41 appears to be useful in other cartridges, such as the 6.5mm Gibbs and the 25-06 Remington. 

            H-570 is a very old surplus powder.  It is an extruded powder that Hodgdon sold in bulk many years ago.  In 1988, some readers reported that their supplies of this powder were beginning to deteriorate.  My own small lot of H-570 came in 1-pound white paper sacks packaged and sold by Hodgdon.  The powder remaining in my sacks does not yet show signs of deterioration.


            IMR-5010 is an extruded powder with very large granules.  I’m not sure if Dupont  (or IMR)  ever sold this powder in canisters.  All lots I have seen have been repackaged.  The labels on some containers have “IMR” as part of the powder’s name; many do not.  Hodgdon sells a version called H-5010.  By whatever name, 5010 is one of the best powders in the 264 Thor with 120- and 140-grain bullets.


            TCCI 5050 is a spherical powder that looks much like H-870, burning just slightly slower.  Surplus powder labeled as pulled from the 20x120mm Vulcan round burns much like TCCI 5050 in this cartridge.  The differ visually, as TCCI  5050 is totally spherical while the surplus Vulcan powder has an occasional tail on the spheres.


            The slowest powder I found usable in this cartridge is called RVO-70 by its distributor, River Valley Ordnance Works, in Harvester, Missouri. This extruded RVO-70 (also known as HC 30) was manufactured for 25mm ammo and is slightly slower burning than most lots of IMR-5010.  A heavily compressed load of 87 grains of this powder under a 140-grain Nosler in the 264 Thor produces about 3265 fps, but extraction is sticky.  RVO-70 is also good with the 155-grain Sierra match bullet.


            Bill Mowrey couldn’t find them in Wichita Falls, Texas, forty years ago, but there are powders on the market today that are too slow for even the 264 Thor.  Accurate Arms sells a powder they call AA 8700, and River Valley Ordnance Works sells one they call RVO Super-Slow.  Both are too slow for most small-arms applications.


            I tested some little-known projectiles.  The Armfield Bullet Co. swages plain and bonded bullets in most calibers and weights.  I used their 90-grain hollowpoint and their 120-grain bonded bullet in these trials.


            The HT  bullet does not contain lead.  It is made form homogeneous stock, similar to the Barnes X Bullet.  The body of the HT bullet is smaller and only the driving bands contact the lands of the barrel.  Such a design is said to reduce chamber pressure because only the driving bards are engraved.  The ballistic coefficients of these bullets are among the highest in the industry.  These bullets are extremely long for their weight.  The 120-grain HT bullet is longer than most 140-grain conventional bullets.


            The 138-grain Lapua bullet actually weighs 138.8 grains on my Lyman electronic scale.  Both the 138- and the 144-grain Lapua bullets are of match design and have recently become available through precision-shooting supply houses.


            After about 200 shots, I removed Mark Pinkston’s muzzlebrake.  Field artillerymen will instantly recognize the bulbous suffix on the barrel.  It has the same profile as the bore evacuator found on 155mm artillery pieces.  This brake matches the barrel on the outside at .654-inch.  It is 2.115 inches long with two 1/2-inch holes drilled at right angles to the bore.  The holes are .222-inch apart, forming two 90-degree planes for the escaping gases to blow against.  One-half-inch of the end of the barrel is reduced to .500-inch and threaded.  The muzzlebrake can be unscrewed with the fingers, although I can’t imagine anyone removing it.  It works well.


            With muzzlebrake in place, an eleven-year-old boy unleashed a 140-grain projectile at 3300 fps and declared the experience “fun.”  Unscrew that brake and the perceived “kick” and noise levels go up.  This same phenomenon occurs with other muzzlebrakes.  The shooter ranks noise and recoil as tolerable.  Anyone standing to the side gets pounded by those gases.  This muzzlebrake can be unscrewed with the fingers, although I can’t imagine anyone removing.  It works well.


            That’s enough technical information.  How do I rate the Thor overall?  It’s what most of thought we were getting when we bought our first 264 Winchester Magnum.  This cartridge, in this rifle, produces about 5 percent more velocity than will the very best 264 Winchester Magnum.  The Winchester Magnum, with a select 140-grain handload, in a select rifle, will reach 3200 fps.  This 264 Thor puissant magnum will almost reach 3400 fps with the same 140-grain bullet.


            An extra 200 fps with the 140-grain bullet does not alter the trajectory much, but it does increase striking energy considerably.  A few cynics still label the 264 Winchester Magnum as “marginal” for elk.  The 264 Thor is not “marginal.”  The quickest way to get a 264 Thor is to re-chamber a 264 Winchester Magnum built on the M700 Remington or similar long action.  Several years ago, I spent good money to set the barrel back on a 264 Winchester Magnum that had a bad chamber.  I’d never do that today.  I’d simply re-chamber it to the 264 Thor.







Grains  Powder
67 IMR-4831
70 MR 3100 (bulk)
70 RL-22
71 IMR-7828
72 AA 3100
72 VV 165
76 H-1000
77 VV 24N41
77 MR 8700
78 H-570
79 H-870
80 IMR-5010
81 TCCI 5050
85 RVO-70




            CCI 250 primers, fire-formed R-P 8mm Remington Magnum brass, 140-grain Hornady Interlok bullets.  Velocities are 3200 to 3225 fps with these charges.


            Warning!  Do not interpret this chart as a bona-fide powder burn-rate chart of the ultra-slow powders.  As chamber pressure increases, some of these powders change position slightly.  Many “surplus” propellants are not canister grade and other lots may vary significantly in burning rate.





Bullet  Wgt. Grs. Load Type Velocity    (Grs./Powder) Comments (fps)


90 Armfield 82/IMR-7828 3828
90 Armfield 85/H-1000 3873


100 Nosler Ballistic Tip 83/H-1000 3710
100 Barnes X 88/H-870 3687   Compressed
100 HT 88/VV 24N41 3727   Compressed
105 Nosler Partition 88/IMR-5010 3673   Compressed
120 Sierra  76/H-1000 3342
120 Nosler Ballistic Tip 79/VV24N41 3367
120 Armfield 84/H-570 3434
120 HT  84/H-870 3491
120 Sierra HPBT 84/IMR-8700 3433
120 Speer 85/IMR-5010 3440
120 Barnes X 85/IMR-5010 3505
120 Remington 87/TCCI  5050 3468
125 Nosler Partition 85/IMR-5010 3481
129 Hornady 85/IMR-5010 3421
138 Lapua 78/VV 24N41 3297
139 Norma SP 85/TCCI 5050 3342
140 Speer 80/H-570 3286
140  Hornady 84/H-870 3364
140 Sierra HPBT 83/IMR-50150 3309   Compressed
140 Nosler partition 87/RVO-70 3267   Heavily Compressed
140 BarnesX 87/RVO-70 3390   Heavily Compressed
144 Lapua 86/RVO-70 3213   Heavily  Compressed
155 Sierra HPBT 83/RVO-70 3073   Compressed
160 Hornady 83/RVO-70 2992



            All heavier bullets were seated to an overall length of 3.66 inches to function through the magazine.  Warning:  Do no capriciously interchange bullets of the same weight.   Some projectiles are so long that they decrease case capacity drastically when seated to function through the magazine.  Components:  Fire-formed R-P 8mm Remington Magnum brass, CCI 250 primers.

            Temperature:  50 to 90 degrees F. 

            Test Rifle furnished by Mark Pinkston; M700 Remington, 26-inch C.P. Donneley barrel, with Pinkston’s own composite stock and PPRS muzzlebrake.


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