October 31, 2022
Mark Twain wrote: “It is difference of opinion that makes horse races.” We have choices in horses—and calibers. O’Connor loved his .270s. Warren Page and Les Bowman were 7mm guys, while Townsend Whelen remained loyal to the .30-caliber. 7mm fans quickly cite that, traditionally, 7mm bullets are longer and heavier-for-caliber than .270 or .30-cal bullets, resulting in higher sectional density (SD).
If bullet construction is equal, then higher SD suggests deeper penetration. Add in aerodynamic shape, and long, heavy bullets have higher Ballistic Coefficient (BC), which translates to velocity retention and flatter trajectory. The benchmark for maximum 7mm performance has long been a 175-grain bullet. Older .270 cartridges cannot compete because the .270 Win., Wby. Mag. and WSM are specified at 1:10 rifling twist, unable to stabilize bullets above 150 grains.
The .30 caliber can compete but only with heavier bullets. The .30s have also long been standard at 1:10 twist, which will stabilize bullets to about 220 grains provided they aren’t extremely aerodynamic, thus too long. So, with standard rifling twists as they have been, traditional heavy .30-caliber bullets can’t beat 175-grain 7mm slugs in the aerodynamics race. In magnum cases, you can push the heavy .30-caliber bullets as fast as large 7mm cases can push 175-grain slugs, but recoil goes up sharply, too much kick for a lot of folks.
For exactly 60 years the 7mm Rem. Mag., nicknamed “Big Seven,” has reigned as the most popular fast 7mm cartridge. Even in 1962 it wasn’t the fastest; Roy Weatherby’s 7mm Wby. Mag., introduced in 1945, edges it by at least 100 fps. However, the Weatherby cartridge remained proprietary—costlier rifles and ammo. Production rifles and factory loads proliferated quickly; the Rem. Mag. took off fast and never looked back; it’s a world-standard hunting cartridge: versatile, flat-shooting and powerful.
With its most common 1:9.25 twist, the Big Seven maxes out with 175-grain bullets. 7mm fans assert that there isn’t much one can’t do with a 175-grain 7mm bullet. To be honest, I really don’t know. I’ve used various 7mm Rem. Mag. rifles off and on for 40 years and used them heavily (though not exclusively) from 1980 through the 90s. I don’t think I’ve ever taken an animal with a 175-grain bullet from Big Seven.
Instead, I generally used medium-weight bullets from 150 to 165 grains. Note: Today’s high-BC bullets didn’t yet exist; the highest BCs were found in 160- to 165-grain bullets. Second Note: I was hunting mostly deer-sized game, occasional elk and never big bears. I found these medium bullets awesome for deer, sheep and goats and perfectly adequate for elk and African game up to greater kudu and zebra. I wasn’t pushing the limits of 7mm performance; I liked the lighter bullets because they didn’t kick as much, and I could push them fast.
In factory loads, the 7mm Rem. Mag. has an average muzzle velocity of 2860 fps with a 175-grain bullet. Loads vary, and it always depends on who is doing the loading. Handloads and select factory loads can be faster, but it’s difficult to get a Rem. Mag. all the way to 3000 fps with a 175-grain bullet. Faster 7mms have long existed. Warren Page’s pet load in his 7mm Mashburn Super Magnum pushed a 175-grain Nosler to a sizzling 3050 fps. Page’s wildcat isn’t the only extra-fast 7mm. In 1987 Remington trumped itself with the 7mm STW, and again in 2000 with with the 7mm RUM. Both are much faster than the Big Seven, but both are significantly over bore capacity.
This is sort of like pushing water down a hose. A hose of certain diameter will only handle so much water. You can increase the pressure, but water flow has a limit. In over-bored cartridges, more powder must be burned for diminishing return. This isn’t the end of the world, but suitable propellants are limited, and increased throat erosion reduces barrel life. Although both have their fans, these factors contributed to limited popularity for the 7mm STW and RUM. It probably didn’t help that both remained largely Remington exclusives; one-horse races are always a bit boring. They have also been standard with 1:9 or 1:9.25 twists, making them unable to accurately shoot heavier than 175-grain bullets.
Walt Berger probably led the way with longer, heavier, more-aerodynamic bullets. Hornady followed with their ELD series, and now most bullet makers have some form of low-drag or long-range bullet, designed for maximum aerodynamics and, if not heavier, are longer than traditional bullets and may need faster rifling twists. Fast-twist barrels aren’t new; any barrel maker can rifle them. Existing 7mm rifles have long been rebarreled to faster twists to take advantage of the longer, low-drag bullets. Cartridges are the next step.
As always, wildcatters led the way, but now we have 7mm factory cartridges designed for the most aerodynamic 7mm bullets, up to 180 grains and beyond. First was the 28 Nosler, based on the RUM case shortened. So far, the 28 has been the most popular of the Nosler cartridges, and it is the only one that has gone beyond Nosler, now loaded by Hornady and Federal Premium. It is over bore capacity, but not grossly so. However, although a standard, .30-06-length cartridge, with the longest and heaviest 7mm bullets, it probably needs a full-length (.375 H&H) action.
ENTER THE PRC
Now meet the long-rumored and just released 7mm PRC, joining the 6.5 and .300 in Hornady’s family of PRC cartridges. Like its siblings, it is based on the .375 Ruger cartridge, .532-inch rim and base. Same as the 7mm Rem. Mag.’s base and belt but, absent the belt, case body is wider, with more capacity. In length, it’s between the 6.5 and .300 PRC, with the case shortened to 2.280 inches. This enables it to be housed in a .30-06-length action, at least with current 7mm bullets. The length and design are about efficiency, avoiding over bore capacity so as to maximize energy yield per grain of powder burned and maximize barrel life—which is of great importance to long-range shooters, who burn up a lot of ammo.
With shorter and fatter case, it is more efficient than the Big Seven, but only slightly faster. Hornady’s 180-grain ELD (X or Match) load is rated at 2975 fps. The 7mm Rem. Mag. with existing 1:9.25 twist cannot stabilize that bullet; the 7 PRC calls for 1:8 twist (or faster), and factory 7 PRC rifles will be so barreled. In bullet aerodynamics, the race is not always to the swift. The 180-grain ELD Match bullet I’m shooting has a shocking, off-the-charts G1 BC of .796, thus with aerodynamics superior to any bullet possible in the 7mm Rem. Mag. (with standard barrel).
Not everybody is a long-range shooter, and not every deer, sheep or elk hunter needs the extra-heavy 7mm bullets. So, I don’t predict a rapid demise for the 7mm Remington Magnum. However, with Hornady’s marketing agility, I predict rapid acceptance and industry adoption. The first factory platform chambered to the 7 PRC is the Mossberg Patriot bolt-action. It took some serious begging to get my hands on one, but that’s what I’m shooting.
The unbelted, fatter case is more modern and efficient. The cartridge will shoot, but I also don’t predict that it be instantly or consistently more accurate than the 7mm Rem. Mag. Manufacturers have 60 years’ experience building Big Seven rifles and cartridges, with myriad loads and generations of load recipes. This Patriot shoots well, initially pushing MOA with the single 180-grain ELD-Match load I have available. But, over the last 40 years I’ve shot numerous 7mm Rem. Mag. rifles that grouped better (and some not as well). With 180-grain bullets, recoil is sharper than with, say, 160-grain bullets (duh)…but not like a fast .30 with heavier bullets.
Which, ultimately, is the attraction of the “new” 7mms, with heavier bullets than ever before, with higher BCs than ever before, but without punishing recoil. It’s not that I intend to shoot game at x-thousand yards. I don’t. But I do believe in bullet weight and SD.
I can’t yet tell you exactly how the 7 PRC performs on game, nor can many folks; it’s just now going into its first hunting season. Hopefully I’ll know more in a few weeks. I can tell you how a 180-grain 7mm performs on game, because this past June I got a detailed lesson. I joined a half-dozen hunters in Carl van Zyl’s camp, John X Safaris in South Africa’s Eastern Cape. Some were friends, others friends of friends, but most elected to not bring guns. Carl had several well-scoped Gunwerks rifles on hand, all in 7mm LRM (Long Range Magnum). Like I said, wildcatters led the way; the LRM is a proprietary predecessor, similar in case dimensions to the 7 PRC, shooting 180-grain 7mm bullets at similar velocity, so similar performance.
Several of these guys were on their first safaris, and you know how that goes. Over the course of a week, I suppose I witnessed 30 animals taken, small to large, close and far. No extreme-range shots were taken, it was too windy, but take ‘em as they come and, with that equipment, we were prepared to take shots as presented. Kudus dropped at 400 yards and more, long shooting in Africa, but the kudu isn’t especially tough. It’s a myth that African game is tougher than ours, but some species are tougher than others. Two of the toughest are wildebeest and zebra. I saw both flattened with one 180-grain 7mm beyond 300 yards—over there, that is thought of as very long shooting.
I was beyond impressed, and that’s why I made a full-court press (and started begging) to get my hands on a 7 PRC as quickly as possible. My prediction: The 7mm Rem. Mag. will remain the more-popular, world-standard cartridge far beyond my lifetime (which doesn’t have all that long to run). Further prediction: The 7 PRC will become more popular than its brethren, and more popular than the faster (but flawed) 7mms that have come along.
In my 40-plus-year career, I’ve been right about acceptance of new cartridges, and I’ve been disastrously wrong. We, the shooting public, are finicky and fickle. Merit alone doesn’t cut the mustard. Still, I predict success for the 7 PRC, an awesome “compromise” cartridge that now has it all: bullet weight, speed and the ranging abilities that are now craved. This cartridge, in my opinion, for the first time since 1962, offers us a difference of opinion in the 7mm horse race. I look forward to spending quality time with it, but, until then, it makes me wish I’d followed Warren Page’s lead and shot 175-grain bullets in my Big Sevens. A lifetime later, now I get it!