To retire a useful rifle is a crying shame, but the rifle in my hands would take considerable work to get it back into the field. The rifle was originally a Winchester Model 70 .300 H&H Magnum, but sometime during its life its chamber had been reamed out to “.300 H&H Ackley Imp.” As was stamped on the barrel.

The Ackley Improved cartridge – with its body enlarged to remove most of the taper and a sharp shoulder formed – is based on the .300 H&H case. P.O. Ackley did not say when he came up for the idea for his cartridge in his Handbook for Shooters & Reloaders, copyrighted in 1962, but it was most likely about the same time as when the .300 Weatherby Magnum was introduced in 1944. About the only difference between the two cartridges is that the Weatherby has a double-radius shoulder, while the Ackley has a more conventional straight shoulder.

A lack of .300 AI cases was the major obstacle to getting the rifle ready to return to the field. Fortunately, a few cartridges came with the rifle to help determine the correct dimensions of the case and that it had, what I thought was, a 40-degree angle on the shoulder.

AI cases are most commonly created by fireforming .300 H&H Magnum cases to remove most of the taper to the case body and form a relatively sharp shoulder. I worried about cases stretching excessively during fireforming, though, because of the large expansion H&H cases would require. Instead, I used a box of once-fired Federal .375 H&H Magnum cases to start the process. I necked them down in steps by first partially running them into a .338 Winchester Magnum sizing die and then a .300 Winchester Magnum sizing die. The bottom of the necks were left a bit wide so cases entered the rifle’s chamber only with some downward pressure on the bolt handle. This false shoulder keeps the cases from stretching during firing.

I tried 72.0 grains of H-4831 with Speer 180-grain spitzers as a fireforming load, but the shoulders were short of fully formed after firing. Increasing the H-4831 charge to 77.0 grains produced fully formed cases.

I realized I started this project a bit backward. Now I had a batch of nicely formed cases but no sizing die to full-length size them. RCBS makes special order dies, so I called RCBS’s Product Marketing Manager Kent Sakamoto and said I needed a two-die set for the .300 Ackley.

 “Your rifle could be chambered for the .300 H&H Magnum Improved with a 30- or 40-degree shoulder angle,” he said.

“It should be the 40 degree,” I replied “I think.”

Kent suggested pulling the bullets and dumping the powder from three of the loaded cartridges that came with the rifle and sending those cases to him along with three fired cases. “I can get them measured up and get you the correct set,” he said.

I surfed the Internet while I waited and found several .300 Ackley shooters who posted it was easy to form Ackley cases from .300 Weatherby Magnum cases, because the only difference between the two was the shoulder. One even said he shot Weatherby factory ammunition in his Ackley. So I ordered 50 new Hornady .300 Weatherby Magnum cases.

Sakamoto got back to me a couple of weeks later and said my cases had a 30-degree shoulder angle, not the 40 degree I had thought. “According to our technician,” he continued, “they are not standard 30-degree Ackley Improved either. Headspace on your cases is short by about .019 inch, and the sizer will be produced accordingly.”

When the RCBS dies arrived, the sizing die was a perfect fit. I turned the die into the press a little bit at a time until the shoulders of the fired cases had been set back .002 inch. The shiny new Hornady .300 Weatherby Magnum cases were about .01 inch shorter at the shoulder than Ackley cases. So all the Hornady .300 brass required was fireforming to convert its double-radius shoulder to the Ackley’s straight shoulder. For that I used 77.0 grains of H-4831 with the Speer 180-grain bullet.

The Ackley book states the .300 Ackley can be loaded using the same loading data as the .300 Weatherby. However, the rifling does not start until a few tenths to upward of an inch forward of the chambers in Weatherby factory rifles that are chambered for Weatherby cartridges. A rifle chamber without this freebore requires reducing powder weights a few grains. The Ackley’s chamber had .20 inch of free run forward of the chamber and beginning of the rifling with Speer 180-grain spitzers seated for a cartridge length of 3.53 inches. So there was at least some freebore, but it was not as much as the .361 inch of freebore Weatherby cuts into its.300 Weatherby Magnum chambers.

The big Ackley case contains plenty of room for a heavy bullet and a hatful of slow-burning powder, plus I had elk hunting plans for the rifle. So I never even considered shooting bullets lighter than 180 grains. For loads I consulted the .300 Weatherby Magnum data in Hodgdon and Alliant reloading manuals and considered my maximum loads would be a couple of grains below the heaviest weights listed in the manuals.

The Speer 180-grain spitzers shot well with several powders. Top velocity was 3,070 fps with 79.0 grains of H-4831 from the Winchester’s 24.5-inch barrel. The extreme velocity spread was 36 fps for three shots. The Hodgdon manual lists 3,096 fps with 81.5 grains of H-4831 from a 24-inch barrel. Close behind was 87.0 grains of H-1000 with a velocity of 3,043 fps. That load had a higher extreme spread of 87 fps, but it shot three of the Speer bullets in .58 inch at 100 yards. That’s pretty good for the old rifle wearing a 4x scope. I ran out of Speer spitzers, so for the load of 79.0 grains of IMR- 7828, I substituted Speer 180-grain Mag-Tips. That load turned in a very even velocity of 2,971 fps, with an extreme spread of 18 fps.

I carefully increased the weight of H-1000 with the Hawk 200-grain bullets, but then impatience and sloth set in, and I jumped the powder charge from 79.0 to 83.0 grains. The first and only shot with that load blew the primer right out of the case. The velocity of 3,059 fps was impressive.

Reloder 25 was close behind with a velocity of 3,025 fps with the 200-grain bullets. That velocity indicates 84 grains of Reloder 25 is also too much, as that speed is about the top listed for the .300 Weatherby in various reloading manuals. However, it showed no signs of excessive pressure like a raised rim around the firing pin dent on the primer, flattened primer face or hard bolt lift. But often those signs of excessive pressure do not show themselves until pressures are far in excess of normal. Retumbo and Hybrid 100 V provided more anticipated velocities, but they turned in extreme velocity spreads in the 90s.

The rifle shot very well with Nosler 220-grain Partition semispitzers. Retumbo and IMR-7828 shot groups under an inch. Extreme velocity spread was 4 fps with Retumbo and 19 fps with IMR-7828. Reloder 22 also had a low velocity spread of 13 fps. Its group was about twice as large as the other two powders, but that may have been because the barrel was still hot. It only takes about three shots to heat up the Ackley’s barrel enough to raise a blur of mirage through the scope, which is like looking down an asphalt highway on a summer afternoon.

After all that work, I have my elk load in the big Partition for the .300 Ackley, and the old Winchester rifle is headed back to the field. I’ll let you know how we fare this coming elk season.