How the .25-284 rates against the competition. L to R: 250 Savage, .257 Roberts, .257 Ackley Improved, .25-284, .25-06, .25-06 Ackley Improved and .257 Weatherby Magnum.

The .25-284 – A Short-Coupled .25-06

The .284 Winchester never broke any sales records, but its strong short case formed the basis for a number of excellent wildcat cartridges. The .25-284 for example, is ideal for rechambering  .257 Roberts rifles built on a short action to gain extra power.

When the .284 Winchester first appeared back in 1963, wildcatters ran around uttering strange cries and baying at the moon. They necked the .284 case up and down for a whole host of calibres – from .224 to .375 and just about everything in between. Robert Hutton, who was technical editor of Guns & Ammo at the time was one of the most prolific wildcatters of the .284 Winchester case and he adapted it for just about every known calibre. His clear favourites, however, were the 6mm-284 and the .25-284. And they are the two that survived and remain reasonably popular right up to the present time.

The .284 Winchester case was a modern concept that came out well ahead of its time. It represented a significant departure from standard  American cartridge design. Larger in body diameter than the .30-06, it had a rebated head of the same  .473” diameter – the first American cartridge to have this feature. It also had a 35-degree shoulder angle,the steepest of any U.S-made factory case and a straight-sided body section that tapered only 0.30 inch in just over 1.50 inches. The body diameter at the extractor groove was  .500 inch, hence the .284 case is only a shade smaller than the belted magnum body size of  .511 inch. Having a shoulder diameter of .475 inch, head-to-shoulder length of 1.775 inches, and 35 degree shoulder angle, the fat dumpy case holds  about the same amount of powder as the much longer .25-06 Remington.

.25-284 2

These four powders performed best in the .25-06, but Win-760’s usefulness was limited to the 75gn bullet.

Additional powder space is not the only advantage of this short, fat case design. The .284 Winchester  case is an exceptionally strong one, especially in that critical area just ahead of the extractor groove where brass is thickest. My load testing with not only the .284 but 6mm-284 and other wildcats showed noticeably less head expansion than is normally experienced with standard rimless brass. Case stretching is likewise minimal. These factors require less  cold working of the brass in resizing and result in longer case life.

Most knowledgeable handloaders realized long before the Short Magnum era began that short, fat, sharp-shouldered cases are more efficient burners of slow powders. I discovered this when I started handloading for the 6.5 Remington Magnum and my 7mm Harvey Magnum based on that case. And it also became apparent to me that longer-grained quick-burning powders tended to burn faster in these cases, thereby generating higher breech pressures for a given charge. Thus, smaller calibres on the .284 case are best served by slow burning powders in the AR2209 – AR2213SC bracket.
Case length of the .25-284 being only slightly  longer than  the .308 Winchester (2.170 inches for the .284 and 2.015 inches for the .308), overall cartridge length is the same at 2.75 inches, allowing both cartridges to work through the magazines of short-action rifles.

The reason for the short overall length of the .284 is that it was designed to be chambered in Winchester’s Model 88 lever- action and Model 100 autoloader. These rifles had short actions with magazines made to handle the .308 Winchester.

For a good many years my favourite deer rifle was a Model 100  Winchester in .284. It gave exceedingly fine accuracy, landing bullets of different weights to virtually the same point of impact. In more recent times, I had MAB rebarrel a BSA Royal bolt action in .284, and with it I was lucky enough to collect an outstanding bull tahr at really long range and a number of trophy deer. I found performance was practically indistinguishable from what I had experienced with the .270 Winchester and .280 Remington. It soon became obvious to me that the .284 was a  modern big-game cartridge and the top choice for building a light mountain rifle.   
My friend Ken Harding wanted to wring extra performance out of his short-action Remington 700 Mountain Rifle in .257 Roberts so he decided to have it rechambered and otherwise modified to shoot the .25-284. The rifle was easy to convert since the two cartridges have nearly the same overall length and no bolt face alteration is needed. The magazine rails have to be opened up to obtain reliable feeding with the fatter case. The .284 case forms an ideal base for this wildcat since all that needs doing is to neck the case down to take .25 calibre bullets without any other change. The case doesn’t need to be blown out or have the shoulder sharpened to gain extra powder space – body taper is already minimal providing maximum capacity for its length, and the shoulder angle steep enough for optimum efficiency in burning slow powders. The case neck too, was already short,  so there was no need to shift the shoulder forward. Nor was there any reason to set the shoulder back in order to lengthen it to gain a longer neck and shorter body. That would have been self defeating, because the body  was already short enough. So in order to form a wildcat   .25-284 cartridge to use in the short-action Remington 700, the only thing that needed doing to the .284 case was to simply neck it down.

The .25-284 is very close to the .25-06 in powder capacity and performance. Comparing the capacity of .284 Winchester and Winchester .25-06 cases revealed that the .25-06 case holds 68 grains of water completely full and the .25-284 holds 66.6gn. Only 1.4 grains less powder is not going to have a noticeable effect on the ballistics,  and the deeper seating required with long, heavy bullets in the .25-284  for the short actions only reduces powder capacity by a negligable amount. These minor differences are not enough to cause a serious reduction in velocity. 

With the 115gn Barnes TSX, the water capacity of the  25-06 is 2.5 grains more than for the .25-284 when the .25-06 is seated to give standard overall cartridge length and the .25-284 to function reliably through the Model 700 short-action magazine. This small advantage in powder capacity and the extra 50mm of barrel length standard for .25-06 rifles actually gives the longer cartridge about 100 fps more velocity at the same pressures.
The handloaded .257 Roberts  is a fine dual-purpose varmint- big-game cartridge, not much inferior to the .25-06. I consider it to be ideal for ferals and deer. My Ruger Hawkeye in .257 Roberts has the same 550mm barrel length as Ken’s .25-284, but is on a long action and long-throated into the bargain. Set up like this, the .25-06 shades it by less than 100 fps. And the .25-284 provides the same kind of performance in a short cartridge adapted to a short, light bolt-action rifle for mountain hunting where every gram and every inch counts.

It seems to me that instead of basing the WSSM cartridges on a much cropped .404 case, Winchester would have enjoyed a greater measure of success if they’d used the .284 as the basis for their new line of cartridges. They’d have fitted in a standard short action and  not required a special action that is handicapped because it can’t be rebarreled to anything except another WSSM.

Many years ago I played with the 6mm-284 and to a lesser extent the .25-284, but I found the .25-284 to be a better dual- purpose cartridge, mainly due to its performance with heavier bullets. Nothing you can load into the 6mm-284 can equal what the  .25-284 can do with 120gn bullets.

A few of the older reloading manuals list loads for the .25-284,most notably the Speer Manuals No’s. 8 and 9 and Hodgdon’s Data Manual No. 26. Comparing Hodgdon’s data for the   .25-284 and .25-06 taken in similar  length 26 inch barrels, revealed that H4350 and H4831 were the most suitable powders with bullets weighing from 100 to 125 grains. Those powders provided a basis for working up loads as they correspond very closely with ADI’s current AR2209 and AR2213SC.

Since the .25-284 is a wild and wooly wildcat, there are naturally some variations in chamber dimensions and hence the loads and the velocities delivered between the various reloading books, including  my own. Incidently, on page 142 of  my manual, the maximum charge of IMR 4350 with the 100gn bullet should be 47gn NOT 57gn, obviously the typesetter erred as I had listed it as 47gn! Speer’s maximum loads for the 100gn bullet were dropped from 54gn for a muzzle velocity of 3331 fps in their No.8 manual to 51gn and 3272 fps in the No.9 manual – a reduction of 3 grains. Loads for both were taken in a Mauser rifle with 24-inch barrel – possibly the same gun, so maybe a different technician had his own idea of what constitutes a maximum load. Bob Hutton’s data split the difference and he listed 53gn of IMR4350 as delivering 3400fps.  Hodgdon on the other hand, had 54gn of H4831 giving the 100gn bullet 3369fps.

Such discrepencies are not unusual with factory cartridges let alone an unstandardized wildcat cartridge like the .25-284 due to differences in chamber dimensions and throat lengths. None of these manuals listed the pressures and velocity readings for it prior to 1970 were rather limited in scope. This was inclined to make the average handloader wonder whether the listings were maximum or merely trial loads.
Ken’s rifle has a 550mm barrel and the standard 1:10 twist. The Model 700’s  magazine allowed a cartridge overall length of 74.80mm and the gun was throated so the bullet missed contacting the lands by about 1/32nd inch. Clem Stevenson’s chambering job was was tight and smooth and  followed published specs closely.

For my own load development I decided to use Win-760 and AR2209 with the lighter bullets and Re-22 and AR2213SC for all other weights. AR2209 is noticeably slower burning than IMR4350,  coming very close to IMR4831. The slower numbers always provided me with the highest velocities in the .25-06 with the exception of the 75-grainer. The .25-284 case does not have a big enough boiler room for a full pressure charge of AR2213SC with that light bullet. Re-22 ran close to AR2213SC with all bullet weights, except the 75gn, where Win-760 took the lead, but the extruded propellant was only slightly behind the ball powder. Overall, Re-22 proved very flexible.

.25-284 4 - Remington Model 700

These are the best powders I found for the .25-284 in this gun. As for accuracy, the Model 700 did best with AR2213SC and Re-22 with all weights of bullets except the 75-gn Hornady and that bullet gave its best accuracy with Win-760. Starting with the 87gn Speer hollow-point TNT and working up to 57gn of AR2213SC I was hoping to attain 3500ps, but 550mm barrel could manage only 3336fps. Speer  recommends this TNT bullet not be driven faster than 3600fps, a parameter that’s not  possible to reach in the test Model 700.

Working up from 55gn of AR2213Sc with the 87gn TNT, charges were increased to 59gn before pressures became excessive so I backed off to 57gn for my working load. This proved  a shade more accurate, although uniformity ran about the same with both loads, averaging only 25 foot-seconds extreme spread. When I started working up loads for the 6.5-284 Norma back in 1991, I soon found that when pressures approached maximum it became a touchy cartridge to work with.  Specifically, maximum troublefree loads could and did develop excessive pressures by the addition of only one more grain of most powders. Using ADI’s temperature resistant  powders  negated any problems that might have been caused by hot climatic conditions.

The .25-284 needs full or near full throttle loads before realizing their full accuracy potential. This trait demands that handloaders work cautiously toward the thin line separating optimum working loads from maximum loads.
Just like with many other small-bore high velocity cases burning hefty charges of slow powders, certain powders become very erratic when loaded to high pressure and a bit touchy when used in full throttle loads. This wasn’t the case with Re-22. I worked up loads with Re-22 with several different bullet weights, and velocity was always about the same or a bit higher than AR213SC produced. Both of the slower powders produced higher velocities than AR2209.

Working up from 50 to 57gn of AR2213SC with the 100gn  Hornady I got  3290fps, but settled for 56gn which dropped only 30 foot-seconds and  gave tighter grouping. – one-minute 5-shot groups. Supreme 780 was tried with 110, 115 and 120gn bullets but gave less velocity and accuracy than the other powders. AR2209 was short on velocity. Win-760 did best with the 75gn bullets but lacked with heavier 87gn.

The design of the .284 case makes it easy to check pressures using the head expansion method. You measure the diameter of the solid web of the head just ahead of the extraction groove with a standard micrometer, because the rebated rim doesn’t get in the way like it does with standard rimless cases. Thus, one needn’t file both sides of the rim and index the face of the case. 

As previously mentioned, .284 cases are strong and pressures were increased until the case web showed the first signs of expansion at 0.0002 to 0.0003 inch. That load could be used indefinitely with no further expansion, but the addition of one more grain of powder added another 0.0002 to 0.0004 inch expansion, and if the same charges were used again, this amount of expansion continued until the primer pocket expanded and became too loose for further use.

Loads worked up to this point developed very erratic pressures, and in a five shot string, two or three cases showed normal pressures while the others expanded primer pockets and showed ejector hole marks and sticky bolt lift. As I mentioned earlier, all powders tested showed rapid pressure rises after working loads were reached, but such increases are predictable when working with slow powders.

The .25-.284 with its overall length held down for use in short actions  gives optimum performance on deer-size game with controlled expansion bullets. In  the .25-06 the 110gn Nosler Accubond and the long 115gn Barnes TSX both give deep penetration, and the various 120gn spitzers are also good, but protrude far down into the case which lowers their efficiency somewhat. In both the Roberts and .25-06 I found the 100gn Nosler Partition to be deadly on fallow and chital deer, and a chest-hit 12-point red stag with a 100gn Partition that penetrated both lungs and lodged against the off-shoulder dropped dead on the spot. Shooting a stoutly structured bullet, the dumpy little .25-284 is fully the equal of the .25-06 on deer and other game of similar size if you land that bullet in a vital area. But if you want to shoot larger, tougher animals, use a cartridge with adequate power for that size game.

.25-284 3 - Loading Data


This article was first published in Sporting Shooter, March 2011.




Like it? Share with your friends!

What's Your Reaction?

super super
fail fail
fun fun
bad bad
hate hate
lol lol
love love
omg omg
Nick Harvey

The late Nick Harvey (1931-2024) was one of the world's most experienced and knowledgeable gun writers, a true legend of the business. He wrote about firearms and hunting for about 70 years, published many books and uncounted articles, and travelled the world to hunt and shoot. His reloading manuals are highly sought after, and his knowledge of the subject was unmatched. He was Sporting Shooter's Technical Editor for almost 50 years. His work lives on here as part of his legacy to us all.