Loading for the .338-06 Ackley Improved

Let’s talk about one of the most underrated big-game cartridges that never caught on like it should have. That is the .338-06 Ackley Improved! For some reason, I’ve wanted this cartridge ever since I first heard about it. But then again, I am a sucker for anything based off, in my opinion, America’s well-rounded cartridge .30-06 Springfield.

First, let’s talk about the history of it. It comes from two different existing cartridges. The parent case is the .30-06 Springfield and from there the .338-06 A-Square was born from wildcatter’s in the late 1950’s necking up the case to fit a .338-diameter bullet. It was founded by Lieutenant Colonel Arthur B. Alphin in 1979 and during the 1980’s, the .338-06 was adopted by the U.S. semi-custom rifle and ammunition manufacturing company, A-Square. The cartridge was standardized as the .338-06 A-Square with SAAMI in 1998 by the A-Square company.

The .338-06 Ackley Improved (AI) is the same cartridge as the .338-06 A-Square but with a sharper shoulder of 40 degrees. This increases its case capacity helping to get a little more powder into the case which in turn increases the velocity and helps with brass life for us reloaders. The .338-06 A-Square’s water capacity in a Remington case is 69.1 grains. The .338-06 AI water capacity in a Remington case is 72.1 grains, making for a 3-grain difference in case capacity. That’s not much but it does allow for a little more powder to get you an extra edge. Plus, there is always the cool factor of the shoulder on an AI case. P.O. Ackley was a notable gunsmith, famous for developing wildcats from parent cartridges like the .30-06 Springfield. Maybe the most recognized one is the .280 AI which comes from the .280 Remington and its parent case the .30-06 Springfield.

The .338-06 AI really makes a great big-game cartridge as it lets the shooter use heavy bullets from 180 grains to 250 grains. When you are in areas that have big brown bears or even a good-size elk, the .338-06 AI really gives you big-game performance and knock-down power without having to use a magnum cartridge. But if you load the lighter 180-grain bullet then it turns into a deer slayer. With a 180-grain Nosler AccuBond bullet going around 2,800 fps, it will put down pretty much any size deer with a well-placed shot and little to no meat waste. It also shoots relatively flat out to 400 yards with a G1 Ballistic Coefficient (B.C.) of .372 sectional density of .225. It is pretty similar to the .35 Whelen but what separates the two is that a .338-06 AI can use longer, sleeker bullets and get up to 100 feet per second (FPS) in velocity. This really helps for flatter shooting. With the .35 Whelen, shooting a 250-grain Hornady InterLock SP-RP with a G1 B.C. of .375 and has a velocity of around 2,450 fps. Using the same bullet design from Hornady 250-grain InterLock SP-RP with a G1 B.C. of .431 has a velocity of around 2,600 fps. Now with that being said, you can get higher B.C. bullets for the .338-06 AI like the Hornady BTHP Match with a B.C. of .670, which is a great Match bullet but not a hunting bullet. Nosler also offers some great options as well like the AccuBond 250-grain with a B.C. of .575 and a sectional density of .313, which is outstanding for a hunting bullet. Barnes also offers a great hunting option with the TTSX 225-grain, all-copper bullet with a B.C. of .514 with a velocity of around 2,650-2,750 fps and sectional density of .281.

The .338-06 AI is a close comparison to the .338 Winchester Magnum, up to that 250-grain bullet. They perform pretty dang close to each other. The .338 Winchester Magnum does average about 100 fps faster at the muzzle with 2,650-2,750 FPS. When both cartridges are zeroed at 200 yards using the same bullet shooting a Nosler AccuBond 250-grain out to 400 yards, the drop on the .338-06 AI is 24.91 inches with 2,262 foot pounds (ft-lbs) of energy. The .338 Winchester Magnum drops 22.89 inches at 400 yards with 2,461 ft-lbs of energy. As you can see there is about a 2-inch difference in drop and 200 ft-lbs between the two cartridges.

One big bonus to the .338-06 AI over the .338 Winchester Magnum is the recoil. Felt recoil on the .338-06 AI with a 6.5 pound rifle using a 250-grain bullet is 40.2 Recoil Energy on the rifle. On the .338 Winchester Magnum, felt recoil with a 6.5 pound rifle using the same weight bullet of 250 grains is 53.28 Recoil Energy on the rifles. That’s a difference of 13.08 recoil energy. So if you’re okay giving up a little velocity for less recoil, the .338-06 AI makes a great medium-to large-game cartridge.

The main downside to the .338-06 AI is there is no factory ammo available, so if you’re not a handloader, the .338-06 AI is probably not the cartridge for you. If you are reading this then I would guess that you understand how much fun a cartridge like the .338-06 AI could be. However, the .338 Winchester Magnum is available in many loaded options from ammo manufacturers. For me, the .338-06 AI is a way around having to mess with a belted cartridge, it is also a lot cheaper on the brass end as you can use .30-06 brass. Good quality .30-06 brass is pretty easy to come by these days and keeps the cost down!

Now let’s talk gun options for a .338-06 AI, because this cartridge has not been SAAMI approved and it still falls into the wildcat category. The .338-06 A-Square was offered in some Remington and Weatherby rifles but if you want the .338-06 AI, you need to get a custom barrel spun up, chambered and put on to an action by a gunsmith or get the tools to do it yourself. I went the route of taking a Remington 700 ADL 22-inch barrel, chambered in .30-06 Springfield, to a gunsmith to ream and chamber it to the .338-06 AI. This was a great option for me as I had a .30-06 hanging out in the safe, so I was able to keep a gun and give it new life. This might be a good option for a lot of people. Most guns chambered in .338-06 A-Square and .338-06 AI use a twist rate of 1:10 but I have seen ones with a 1:9 twist which would help to stabilize the heavy bullets.

Okay, let’s talk about what we really want to talk about! Handloading for .338-06 AI.

Right now, components are not that easy to obtain and if you can they are not as cheap as they were 3 years ago when powder was 30 bucks a pound and a brick of primers were 34 bucks. So, I have decided to do brass the economic way; I happen to have a heap load of once-fired .30-06 brass. Since using .30-06 brass, I will have to fire form it to the .338-06 AI chamber, so I will load some light loads before I can really get into my load work up. I start off by annealing the brass to expand the neck enough to fit a .338 bullet. If you do not anneal the brass before sizing, the once-fired brass is work hardened, which can stress the brass neck and cause it to crack on sizing. Annealing brass also adds life and better neck tension. Once the brass has been full-length sized, I check to see if it needs to be trimmed. For some reason, AI cartridges seem to not grow like other cartridges. I almost never have to trim AI brass. Once that step is done, it’s time to prime. My choice for that is on my Forter Coax press. It’s really easy and fast to use and you can feel the primers seat just right.

Next step is powder. Once I have decided on what powder to use, I weigh that out on my Frankford Arsenal intellidropper and then set up my seating die. Once the die is set, it’s time to seat bullets for fire-forming the brass. For this, I am just using a hard-cast, 225-grain cast bullet as I am not shooting for groups. A lot of people think this is a waste of components, but I am a firm believer that any time you spend behind a gun is never a waste as you are building your skills! Also, you get out and shoot and in my book that’s never a waste. Once I have hit the range to fire-form the brass, it’s time to repeat all the steps above again.

Brass formed from .30-06 Springfield brass to fire formed to the .338-06 AI chamber.

Now for bullet options and powder. There is a good selection of bullets in the .338 line. Barnes offers some great options for hunting, like Triple-Shock X (TSX) bullets .338-Caliber 210-grain, hollow point boat tail, Tipped Triple-Shock X (TTSX) Bullets .338-Caliber, 225-grain spitzer boat tail or the LRX Long-Range hunting bullets .338-Caliber, 250-Grain LRX boat tail. All of these options are great choices for hunting! The TSX is my main bullet of choice to hunt with if I can get it to shoot around 1 inch out of a hunting rifle. They are lead-free and in my experience, I have seen these bullets expand and get the job done all the way down to 2,200 fps.

Nosler also offers some great options for hunting, like the 180-grain AccuBond SP, 200-grain Expansion Tip (Lead-Free), 200-grain Ballistic Silvertip, 225-grain AccuBond SP, 250-grain AccuBond. I personally have great luck on big game using the Ballistic Silvertip bullet.

Hornady offers a mix of both hunting and target bullets. Hunting bullets like CX bullets Polymer-Tip, Copper-Expanding boat tail (Lead-Free) is a new bullet that I have not had a chance to test. They offer it in a 185-grain and a 225-grain .338 bullet. Hornady offers a more traditional hunting bullet - the InterLock 225-grain Spire Point and ELD-X Polymer Tipped boat tail which is becoming more and more popular with people hunting long range.

For their more target and precision bullet, they have the ELD Match polymer-tipped boat tail bullet.

Speer offers three different bullets all of which I like. Speer’s Hot-Cor Spitzer 200-grain is a great cheaper option (and in my experience been pretty accurate), the Spitzer boat-tail, 225-grain and Grand Slam 250-grain.

Projectiles used in testing.

Now for primers. Right now, primers are like gold or maybe even rarer. But when it comes to this cartridge, I have found that you should use what you can find for large rifle primers. There is no need for magnum ones. For me, I like to use Federal Gold Match GM210 but they are getting tough to find.

For powder, this cartridge allows you to have a good variety of options. Here are some of the few I have found to be the best performers for me: Hodgdon Varget, H-380, H-4350, IMR-4064, IMR-4831, RamShot Big Game and Reloder 15.

My test rifle is a Remington 700 ADL with a 22-inch barrel and a Leupold M8-4x fixed power scope. The barrel is free-floated, and the action is bedded in the stock. The gun weighs in at 6.5 pounds.

In my testing I found the 225-grain bullets shoot best with a slower burning powder like H-4350 and IMR-4831. Although some of the medium burn rate powders did well, like Reloder 15 and IMR-4064. I did a lot of testing from 200-grain bullets up to 250-grain bullets with eight different powders and three-shot groups. The best results were with the Nosler AccuBond 225-grain. Shooting an average of a .73-inch group with a muzzle velocity of 2,601 fps average. Velocity was measured with a MagnetoSpeed V3 Ballistic Chronograph.

To sum it up this is a fun round to load and shoot with. It holds its own when put up against magnum cartridges. It has less recoil yet still has great knock-down power at hunting range. The downside is that there is no factory ammo made, and no rifles chambered in .338-06 AI. For us that have this cartridge, we really know the joys of loading and shooting it.