HAM'R Time - Hard-Hitting Horsepower for Your AR
August 21, 2018
Wilson Combat's new .300 HAM'R is to the .300 Blackout (BLK) what the .300 Win. Mag. is to the .308 Win. All it takes is a barrel change.
There will no doubt be a fair degree of internet angst over this new .30-caliber AR-15 cartridge with the predictable refrains of "it's just marketing" and "it doesn't do anything my .300 BLK doesn't do." No, it isn't and yes, it does (respectively).
Like many of you, I remain in love with the AR-15 but I was content with the rifles I already own. I was also skeptical of a new chambering in this still extremely popular, albeit slow-selling rifle, at least as of late. I already own rifles in 5.56x45mm, .300 BLK and 6.5 Grendel. I thought I was done.
The new .300 HAM'R offers a big step up in terminal performance over the .300 BLK by offering anywhere from 100 to 300 feet per second (fps) increase in velocity. That's from factory-loaded offerings using the same bullet weights and same barrel lengths.
Bill Wilson lives on a plot of land that allows him to shoot and hunt freely. He loves the AR-15 and has been tinkering with a cartridge that maximized terminal performance from it using standard receivers, bolts and magazines.
The .300 BLK is a great little cartridge, but it was designed around heavy, subsonic bullets and the use of lighter 110- to 130-grain supersonic projectiles was an afterthought. Velocities for the .300 BLK with those bullet weights are anemic because you can't get enough slower-burning rifle powder into the case to get close to maximum pressure. The case isn't big enough. Faster pistol powder is required to get close to max pressure and those powders don't generate much gas volume, hence the .300 BLK's weak velocities for a rifle cartridge.
Wilson's first foray into this optimization problem was with the 7.62x40mm Wilson Tactical (WT). This cartridge was designed by Kurt Buchert, then brought to market by Wilson Combat, working with all 110- to 135-grain bullets. Some of those bullets have long ogives (noses), so case length is limited to 1.565 inches.
Wilson knew if he could make the case a little longer and redesign the chamber to allow for lighter bullets to be seated further out, he would pick up a ton of velocity from the increase in case capacity. That's exactly what happened with the .300 HAM'R.
The .300 HAM'R case is .040-inch longer than the 7.62x40mm WT and .260-inch longer than the .300 BLK. The HAM'R's longer chamber throat means less when using bullets with long ogives, but it allowed Wilson to seat the lighter and stubbier .30-caliber bullets out quite a bit further. Longer seating depth combined with a longer case freed up massive amounts of case capacity. The only variable remaining was what powder to use with the new cartridge.
Most factory loadings for the .300 BLK use powder designed and commonly found in pistol cartridges. Hornady's loading manuals even list the .300 Whisper in the "Handgun" section.
Putting pistol powder in a rifle cartridge is unusual but it works with the .300 BLK because Hodgdon's H110 allows for close to max pressure in limited case capacity when using 110- to 135-grain projectiles. The HAM'R's longer case and thoughtful chamber design generated lots more case capacity. That extra case capacity meant that slower-burning rifle powders were now a viable choice.
Slower-burning rifle powders are preferred when striving for supersonic velocity because slower powders generate more gas volume and that increased volume is what pushes the bullet. The down side is the slower powders require more cartridge capacity (internal volume) than faster powders when powder charge weights are kept equal.
The powder that proved ideal with the .300 HAM'R is Hodgdon's CFE BLK. Hodgdon developed this powder for the .300 BLK to provide a slower-burning option than H110. CFE BLK does very well with the 200-grain and heavier bullets, but you can't put enough of it in a .300 BLK case to get to the ideal pressure with 110- to 135-grain bullets. When Wilson made the larger .300 HAM'R cartridge, it had the ideal volume to hit max pressure with CFE BLK. It was a match made in heaven.
Because CFE BLK is slower and bulkier than the same weight charge of H110, it generates more gas volume and helps get those awesome .300 HAM'R velocities. When compared to the .300 BLK, the .300 HAM'R offers significant performance increases across all bullets weights from 110 to 150 grains. The accompanying table shows my personal testing of factory-loaded ammunition from these two cartridges. Barrels in both test guns were 16 inches long.
I saw about a 160 fps increase with the lighter 110-grain bullets, but the 125-grain projectiles showed major velocity differences. Black Hills 125-grain Tipped MatchKings had a muzzle velocity of 2197 fps, measured by my LabRadar. The same LabRadar measured a whopping 2501 fps with Wilson's 125-grain TNT load. That's over a 300-fps difference and a significant difference in both trajectory and energy delivered on target.
The math of the .300 HAM'R doesn't lie and it can't be manipulated. It is a much more powerful cartridge than a .300 BLK and the reasons behind it are the greater case capacity through solid design work, selecting bullets that can be seated longer in the case and the ideal conditions for use of CFE BLK powder.
While all it takes is a barrel change to get any AR-15 to shoot the .300 HAM'R, the test rifle came complete from Wilson Combat. The test rifle is the Ranger model, complete with a 16-inch barrel. Some folks are going to look at the 1:15-inch twist rate of the barrel and scream for a tighter twist since that's all the rage these days. At moments like this, I'm glad Bill Wilson is no rookie and continues to do what is best instead of what is popular.
Not too long ago, a .308 Win. had a twist rate of 1:12 and they worked just fine with bullets weighing up to 168 grains. Since the bullet weight on the .300 HAM'R is anywhere between 110 to 150 grains, a 1:15-inch twist makes perfect sense to me. The accuracy table clearly shows that there are no stability issues with this twist rate.
The Ranger model is the quintessential "do-everything" AR. It has a tapered barrel contour that is light enough to carry for long periods of time yet retains enough mass to handle long firing strings. The billet receivers are so well machined they practically "click" together, and the lightening cuts on them only enhance their beauty.
The barrel has a mid-length gas system that sits under a 12-inch, M-Lok handguard. The handguard is a trim little thing that sits comfortably in the hand. Wilson Combat's Tactical Trigger Unit (TTU) is crisp and the Armor-Tuff finish is easy on the eyes while being hard to wear out. In short, the Ranger and the .300 HAM'R are perfectly complementary.
There's always room for any product that offers unrivaled performance and that is why I'll be buying this Wilson Combat rifle. The .300 HAM'R represents the high-water mark in standard AR-15 terminal performance.
Wilson Combat Ranger
Type: Direct impingement, semiautomatic
Caliber: .300 HAM'R
Capacity: 10, 20, 30 rds.
Barrel: 16 in.; 1:15-in. twist
Overall Length: 33.5 in. (collapsed), 36.5-in. (extended)
Weight: 6lbs., 4 oz.
Length of Pull: 11.75 in. (collapsed), 15 in. (extended)
Finish: Type III, hardcoat anodized and Armor Tuff
Safety: Two-position selector
Manufacturer: Wilson Combat