How to Handload for the 300 HAM'R

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The .300 HAM’R cartridge has been around for several years and has even received SAAMI (Sporting Arms and Ammunition Manufacturer’s Institute) approval. However, there are not a lot of factory loads to choose from. So, if you’re a .300 HAM’R owner, handloading is something you’re probably considering. The first rule of handloading for an AR-15 is that you must work within the magazine limiting 2.26-inch overall length. The .300 HAM’R’s case is 1.603 inches long, so that only allows .657-inch of bullet protrusion. This means bullet selection is critical; those long and slender bullets so popular today just won’t work.

I’ve been shooting an AR-15 in .300 HAM’R since Wilson Combat introduced it. Initially, I purchased a good supply of ammo, but it has dwindled, so I decided to embark on a handloading journey with two goals in mind. First, I wanted a load I could rely on for deer hunting. Second, I wanted an affordable load for practice and play. Sometimes, handloading projects can become unpleasant ordeals never producing the desired results. This project was not one of those, but before I go into detail, some history for those unfamiliar with the .300 HAM’R is in order.

.300 HAM’R History

Like most cartridges, the .300 HAM’R evolved from another cartridge. If we go back to the beginning, the first cartridge with a .378 rim diameter was the .222, which Remington introduced in 1950. As they say, the .222 Remington begat the .221 Fireball (1963), which begat the .300 Whisper (1990), which inspired the .300 Blackout (2009). The Blackout is often thought of as the .30-caliber AR-15 cartridge and as similar to the .300 HAM’R, but the HAM’R evolved from the .223 Remington, which descended from the .222 in 1962. Ultimately, the .300 HAM’R was introduced in 2018, but its next closest kin is the 7.62x40WT.

What’s the 7.62x40WT? It was a cartridge designed for Wilson Combat in 2011. Bill Wilson, Wilson Combat’s founder, is an avid hunter, especially for feral hogs. Bill had tried all the AR-15 compatible cartridges of the time, and though he liked the .30 Remington AR, brass was — and is — as scarce as unicorn poop. Bill didn’t want to pick up brass in the middle of the night while slaying hogs, and he was lukewarm on the Blackout. So, the 7.62x40WT was born, and just about as quickly, it was forgotten.

Bill altered the 7.62X40WT case to hold a bit more powder and created the .300 HAM’R, which, with sponsorship from SIG Sauer, was SAAMI-approved in 2020. SAAMI lists the .300 HAM’R at 57,500 psi, with an instrumental velocity of 2,450 fps with a 125-grain bullet. By comparison, SAAMI specs for the .300 Blackout list a maximum average pressure of 55,000 psi with an instrumental velocity of 2,280 fps with a 123-grain bullet. Though the .300 HAM’R has yet to gain widespread acceptance, it’s a popular cartridge in rifles from Wilson Combat, and you can easily convert your .223/5.56 AR-15 to .300 HAM’R. However, other than Wilson Combat and Lehigh Defense, there’s not many options for factory ammunition.

The Handloads

Before I began the project, I reached out to Bill Wilson for advice. Hodgdon lists four suitable powders for the .300 HAM’R, and Bill said not to waste time screwing around and to just go with CFE BLK. I started with 100 rounds of new brass all primed with CCI 450 Magnum small rifle primers, four Lehigh Defense bullets tailored to work with the .300 HAM’R, two Hornady bullets, and one Barnes bullet. My rifle is a Wilson Combat Protector Carbine with a 16-inch barrel that’s outfitted with a Trijicon 1-4X AccuPoint with a post reticle. I conducted all the test firing with the AccuPoint set at 4X, and I also outfitted the rifle with the new MeatEater suppressor from Silencer Central.

I started with the 125-grain Lehigh Defense Tipped Controlled Chaos bullet and worked up from 26.5 grains to the 27.6-grain maximum Hodgdon lists for a 125-grain bullet. I set the overall length for that load at 2.256 inches and did not alter the seating depth for the other three Chaos bullets; they just ended up at whatever length the setting for the 125-grain bullet put them at. I loaded the Hornady 125-grain SST and the 110-grain Barnes TSX bullets to an overall length of 2.256 inches.

Maybe the most interesting load was the one I wanted for plinking, practice, and play. For some reason, I had a box of 110-grain Hornady .308-caliber FMJ bullets on hand and thought they just might work. I shoved them ahead of 27.0 grains of CFE BLK, and not only did they feed phenomenally, but they also shot to nearly the exact point of impact as the 115-grain TXC load, which I think I’ll ultimately use for deer hunting. Sadly, it appears Hornady no longer manufactures this bullet, so if you want some, you’d better get to them before I do. At the time of this writing, they’re available from several online retailers.

I could have tweaked each load a bit for a little more velocity and probably even more precision by adjusting the overall length, massaging the powder charge, or even by using different primers. However, there’s no guarantee the same recipe would provide the same results in your rifle. You can easily tune these loads to work your gun on your own; they serve as a great point of departure for your personal .300 HAM’R handloading project. The way it all turned out, I see no need to mess with the 115-grain Chaos load or the Hornady FMJ load. They both shot into less than an inch and will do what I need done.

What I Learned

Several things stood out and should be obvious to even an inexperienced reloader. The first was that the .300 HAM’R cartridge — with the CFE BLK powder — is simple and straightforward to load. Just dump in an appropriate amount of CFE BLK powder, seat the bullet (a short bullet) to an overall length of less than 2.26 inches, and start shooting.

The other thing that was obvious is the Wilson Combat Protector Carbine is an excellent shooting rifle. I fired seven different first-run handloads, and the average group size for the seven three-shot groups was an impressive .978 inch. That’s amazing, but so was the fact that I overlaid all seven groups on a single target, and the aggregate group size for all 21 shots with seven different loads/bullets ranging in velocity from 2,150 to 2,530 fps was less than 2.5 inches.

It’s a shame the .300 HAM’R does not get more attention from gun scribes and even firearms and ammunition manufacturers. As far as I’m concerned, it’s the best big-game cartridge you can chamber in an AR-15 — unless you want to shoot out to silly distances. It’s also perfectly suitable for self-defense and recreational shooting. A little birdie tells me a major ammunition manufacturer will soon be offering a new factory load for the .300 HAM’R, but until then, there are lots of handloads you can craft. If you have a Wilson Combat Protector Carbine, I expect they will all shoot the cents off a quarter at 100 yards.

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