[RETRO] .223 and 6mm-223 Load Data for Long-Range Handgunning
September 16, 2019
The .223 Remington, a NATO cartridge, and the 6mm-223 (6x45), a wildcat, are both performers for long-range handgun shooting; here's load data for each cartridge.
This article originally appeared in "Guns & Ammo" April 1982 issue.
Hunkered down behind a clump of big sage, I opened the action of my custom XP-100 Remington and dropped a 6mm-223 (6x45) round into the chamber. I don't trust safeties, so I slipped the bolt forward, but didn't lock the action. When the time came to shoot, simply camming the bolt handle down would ready the pistol for instant action.
Before moving, I checked the country around me. There wasn't a pronghorn in sight. Brilliant midday sun flooded the huge basin and glinted on the sheer rock cliffs of the Oregon Buttes that towered majestically above the plains some four miles to the north. I stood up and, with the XP-100 held muzzle-down in my right hand, set a course for the low ridge that hid me from my quarry- a massive-horned Wyoming pronghorn that I'd been stalking for over an hour. With any luck, he'd be just 75 yards beyond the ridge.
Drawing near the ridge crest, I dropped to my belly and crawled up to where I could glass the country beyond. Damn the luck! The buck and his smaller companion had moved off and were now feeding peacefully some 200 yards away. To make things worse, there was absolutely no way that I could stalk any closer without being observed.
I slipped the daypack off my shoulders and very carefully inched it into position atop a bush where it would provide an excellent rest for my pistol. I wasn't too concerned about hitting the pronghorn from such a good position, but I had some doubts about the 6mm-223 (6x45) cartridge I was using. I'd wrung it out thoroughly on chucks and prairie dogs in the preceding months, but I had no idea how it would perform on big game. The cartridge was loaded with a Sierra 85-grain hollowpoint boattail bullet pushed out the muzzle of the 14-inch barrel at 2,754 fps (feet per second) by 24.5 grains of Hodgdon's H322 powder. Would the little 6 mm have enough oomph to anchor a pronghorn?
There was only one way to find out. I estimated the range at 200 yards. With the pistol sighted dead on at 100 yards, the bullet would hit about 4½ inches below point of aim at that distance. Allowing for the drop, I steadied the crosshair of the Redfield 4X pistol scope just behind the buck's shoulder and squeezed the trigger. The XP-100 bucked gently in my hand and I heard the bullet hit, but it wasn't the reassuring "thunk" of a solid hit. The buck jumped, pranced forward a few steps and turned slightly toward me. Too low! I'd hit too low. The buck was farther out than I'd figured.
Ramming another round home, I aimed again, but this time the horizontal wire of the reticle rested atop the buck's back. At the crack of the pistol the buck whirled, sprinted for about 20 yards and stacked up. On my way to the buck, I paced the distance at 279 steps. Allowing for some error, the buck had been at least 250 yards away, accounting for the low hit on my first try. An autopsy revealed that the first shot had hit the antelope low in the brisket. The bullet had passed through, opening quite a wound, but its path was below the lungs and behind the heart. The second shot, though, was right where it should have been. The bullet smashed a rib going in, knocked out the lungs, angled back through the liver and exited, leaving an exit wound of about .35 caliber in diameter. The bullet had held together and I recovered not one piece of jacket or core.
Why was I out there stalking big game with a 6mm-223 (6x45) pistol? The answer is simple. I had to know what the little cartridge would do on deer-size game. As with rifles, there are two basic theories on handgun cartridges. Some hunters swear by the big bores. They thrive on heavy recoil and a booming muzzle blast and are content with the low-velocities and rainbow trajectories that go hand in hand with big bores. Me, I prefer high velocity and a flat trajectory and I've taken enough game of all sizes with a variety of handgun cartridges to know that when the proper bullet is used, a fast, small-bore cartridge is every bit as effective on game up through elk in size as any big bore and for the most part, the small ones are a lot more accurate.
Thus we arrive at the subjects of this article, the performance of a couple of high-velocity, small-bore cartridges in handguns- the popular .223 Remington and a wildcat, the 6mm-223 (6x45). Both cartridges generate high breech pressure- in the neighborhood of 45,000 to 50,000 psi- so until the advent of such pistols as the Contender and the XP-100, they couldn't even be considered by handgunners.
The .223 Remington, or 5.56 mm as the military calls it, is a natural for a pistol. It's been around since 1964 and has become firmly entrenched m the U.S. shooting scene. Because it's both a military and a commercial cartridge, its popularity is guaranteed. Brass is easy to come by and it's such a good performer in rifles that it has pushed the .222 Remington Magnum completely out of the picture and has done a fair job of taking over the hunting scene from the less powerful .222 Remington, the latter still being the favorite in bench rest circles, though.
However, you don't just take a .223 Remington, as loaded for rifles, and get top performance from it in a pistol. Powders must be chosen that will burn efficiently in the shorter pistol barrels and on the whole, .224-inch bullets of medium weight will give better performance than the heavier ones. As of this writing, Thompson/Center Arms offers both ten-inch and Super 14-inch .223 Remington barrels for their Contender pistol and such companies as Wichita Arms and M-S Safari Arms will chamber their superb bolt-action pistols for this cartridge.
Naturally, the .223 Remington is strictly a varmint cartridge, but for this purpose it has few peers. I couldn't begin to count the number of rock chucks and prairie dogs that I've taken with my .223s and I've rolled some at distances that never fail to surprise me. While hunting with the boys from Sierra Bullets at Goodland, Kansas last summer, I anchored a prairie dog at 350 yards while shooting my Wichita .223. My hunting partner, John Moeller, has a 320-yard prairie dog kill to his credit with his Super 14 Contender and the number of 200-yard kills we've made on varmints are so many as to be commonplace. The cartridge is also an excellent choice for handgunning coyote-size varmints and I'll guarantee that it'll put them down quickly at 200 yards plus.
The accuracy of the .223 in a pistol is almost good enough to be phenomenal. With any of my pistols, 100-yard groups measuring right around one inch are common and I won't settle for anything over I½ inches. However, this accuracy is attained only through very careful load development. But even then your most limiting factor on accuracy is the scope on your pistol. The long eye relief designs available today are certainly a big improvement over those of just a couple of years ago, yet the most powerful is 6X. For long-range work on small varmints I prefer 4X and 6X, yet these are a far cry from the high-powered models riflemen use to achieve tack-driving accuracy.
As I've said, good handloads are the key to top performance from the .223 Remington cartridge in a handgun. The accompanying table lists the loads that I've found produce the desired performance in my pistols. For small varmint shooting, the Sierra 50-grain medium-velocity Blitz bullet and Hornady's 50-grain SX are your best choices. These bullets will give the desired explosive expansion at pistol velocities and will shred a small varmint even when your shot is off target a little. But for days when the wind is blowing, I usually opt for the better wind-bucking qualities of 55-grain bullets. The 55-grain numbers are also best on coyotes and cats where you want to damage the valuable pelt as little as possible. Some very spectacular velocities can be obtained with 40- and 45-grain .224-inch bullets, but these lightweights don't have good ballistic coefficients, so they shed their velocity very fast and they're poor in the wind.
There are a few very important facts that you must keep in mind about the .223 Remington as a handgun cartridge. First, you'll get acceptable accuracy and velocity using nothing but factory loads. However, factory fodder won't give you peak performance. The burning rate and charge of powder used in factory loads are carefully chosen to give optimum performance in a rifle. In a short pistol barrel these powders won't burn efficiently. You'll get your best results only with good handloads.
Second, powders that give a good combination of accuracy and velocity in a 14-inch barrel are often total washouts in a ten-inch barrel. This is particularly true of such slow burners as H335 and 4895. It's nearly impossible to burn all of these powders in a ten-inch barrel, so velocities are quite low.
Third, powders that burn uniformly in a 14-inch barrel will sometimes give erratic performance in a ten-inch barrel. Out of a string of 10 rounds, six or seven will burn normally and produce velocities 11 or 12 percent lower than in the longer barrel. But in the other three or four rounds the powder doesn't burn completely and velocities will drop as much as 1,000 fps below that of the same load in a 14-inch barrel. When this happens, accuracy goes all to hell. In my .223s I find H322 consistently produces the best accuracy/velocity combination with all bullet weights and styles. Close behind it is H4198. However, I do a lot of loading and prefer to throw my loads through a measure to save time. Because 4198 stacks like straw in a measure, it doesn't meter accurately and charges must be weighed to guarantee uniformity. Hodgdon H335 and 4895 give good performance only in a 14-inch barrel while N200 works well in both lengths.
The 6mm-223 (6x45) is a wildcat cartridge that represents a logical step up in caliber from the .223. It's not really a new idea, but the cartridge is one about which very little has been written. In performance it's on a par with the 6x47, a cartridge based on the .222 Remington Magnum case that benchrest shooters have been playing with for some time. Similar performance will also be attained with a 6mm PPC in a pistol. Of these, though, the 6mm-223 (6x45) holds the greatest potential for the handloader owing to the availability of .223 Remington brass.
Because the 6mm-223 (6x45) is a wildcat, there are a number of versions floating around, the differences between them being mostly in shoulder angle and body taper. The one about which I'm writing is nothing more than the .223 Remington necked up to 6 mm. None of the other dimensions of the parent case is changed. My pistol is a 14-inch barreled XP-100. The barrel is a custom job made up for me by Trapper Alexiou of Trapper Gun, 18717 14 Mile Road, Fraser, Michigan 48081, from a Douglas barrel blank. The Fajen walnut thumbhole stock was fit and finished for me by Ralph Hastings and my dies were provided by Dick Bebee of Redding.
Forming 6mm-223 (6x45) cases is a cinch, a job requiring no form die. You simply run a .223 Remington case through a 6mm-223 (6x45) full-length sizing die. While the step up from .22 to 6 mm is a minor one, some alteration of most expander balls is necessary if you are to avoid wrinkling some cases at the mouth. This is because 6mm expander balls normally have an undersize knurled section on them just above the decapping pin. Even though this section is undersize, it can be anywhere from .001 to .008 inch larger than the inside diameter· of a .223 case mouth. The size of this knurled section varies with the make of the die, but if the standard expander is used to swage up new, unfired .223 cases to 6mm, the knurled section usually resists entering the case mouth and will often wrinkle the neck, ruining the case. Redding provided me with two expander balls, each with a diameter of .242 inch. One is a standard design while the other is smooth and 'tapers to maximum diameter rather gradually. The latter does a slick job, entering the .223 mouth and swaging it out to 6mm with nary a hitch. After the initial forming, the standard expander can be used for all subsequent reloading.
Since there is no alteration to the .223 Remington case except to open up the mouth, there is no time consuming, costly fire-forming involved with the 6mm-223 (6x45). Once the cases are run through the full-length sizing die, they're ready to load. The maximum length for 6mm-223 (6x45) cases is 1.760 inches, the same as the .223 Remington. In the forming operation a new .223 case will shrink about .005 inch due to necking it up, but don't let this bother you. It'll stretch out as it's fired and when it reaches 1.760 inches, trim it back .010.
Like the .223 Remington in a pistol, the list of powders that will give satisfactory results in the 6mm-223 (6x45) are limited. The slower ones, H335, 4895, N201, etc., produce decent accuracy, but not optimum velocity. Two powders are best in my XP-100, H322 and H4198. The accuracy with both of these is excellent. However, H322 consistently produces the best combination of accuracy and velocity.
The enclosed table lists the better loads I've worked up for my XP-100 6mm-223 (6x45). Those using H322 and H4198 are the most accurate. All of these loads are near maximum in my particular barrel and could develop dangerous pressure in any other chamber. Therefore, the powder charges should be reduced ten percent for any other pistol.
Conspicuous by their absence from the table are loads for 6mm bullets weighing 90 grains or more. The reason for this is that I couldn't find any load with 87- to 105-grain bullets that is accurate in my pistol. When I was considering this cartridge, I visualized it only as a varmint number, so when I discussed the project with Trapper I talked of a twist rate of one-in-14 inches. This is exactly what I have and it has proved to be a mistake. The slow twist is great for bullets weighing 60 to 85 grains, but it won't stabilize anything heavier. Heavy bullet accuracy is very poor in my pistol and certain ones have a tendency to keyhole at 100 yards. A twist rate of one-in-ten inches would probably suffice to stabilize the heavier bullets and I doubt that it would have any adverse effect on the performance of lightweight designs.
As it turned out, my choice of the wrong twist places a serious handicap on my use of the 6mm-223 (6x45). The cartridge isn't just a superb varminter, but in fact has considerable potential for use on deer-size big game. Last fall I not only bagged that pronghorn as described in the beginning of this article, but a dandy four-point mule deer fell to one shot at 190 yards. The load was the same one I used on the pronghorn. In both instances, bullet performance was excellent and the animals went down for keeps. However, both bullets were able to do their jobs without having to break much bone to reach the vitals. When a shoulder must be broken, I'd feel a lot better with a 100-grain bullet loaded in the 6mm-223 (6x45).
As my 6mm-223 (6x45) is rigged, it's at its best as a long-range varmint pistol. The accuracy is there-minute of angle with a variety of bullets-and those lightweight 6 mm offerings are explosive on the smallest of game. My favorites for varmints of all sizes are 70- and 75-grain bullets. The little 60-grain Sierra is excellent, but because of its low ballistic coefficient, it's not a good long-range choice.
Why even bother with the 6mm-.223 (6x45) on varmints when the standard .223 Remington is such a good cartridge? The answer to this should be readily apparent if you study the load tables for a minute. Bullets in 6mm can be pushed almost as fast from the 6mm-223 (6x45) as .224-inch offerings from the .223 Remington. On a calm day, the .223 will hang right in there with the 6mm version, but when the wind is whooping it up, as it often is here in Wyoming, the 6mm-223 (6x45), with its heavier bullets, eliminates a lot of guesswork.
Both the .223 Remington and the 6mm-223 (6x45) have their advantages and disadvantages for the shooter. My 6mm-223 (6x45) is undoubtedly the most accurate pistol in my battery and it's versatile in that it can be used on both varmints and deer-size big game. However, it's strictly a custom job from chambering through handloading and this adds up to considerable cost. The .223, on the other hand, is a commercial offering. Production guns are chambered for it and you need not be a handloader to shoot the .223. Which of these cartridges you choose, then, will be governed by your shooting needs and your budget. But whichever you select, I can guarantee you'll be satisfied. The two cartridges mark another big step forward for long-range handgunning enthusiasts.