Where does a fella sit if he has both…
On the naughty step, alongside me when I come home with another rifle I don’t need and the wife finds out.
It is amazing how many rifles I’ve bought for her, as presents. Look what I got you, wife! Cue rolling of eyes and a frosty glare. Mind you she is a lethal shot with everything I’ve ever “given” her.
I shoot deer with everything from a .223 Rem to a .300 WSM, and a bunch of rifles in between in 6mm, 6.5mm, 7mm and regular flavour .308. I’ve had a bit of a clear out in the last year and got rid of a .270, a 6.5 Creedmoor and a .243 Winchester, and fairly shortly I will also be giving back the two 7mm rifles I’ve been babysitting while a mate works overseas. Give or take they all do the same thing, assuming you use them in the same way.
Sometimes on a long day with variable conditions from woodland to long-range, between two of us we might have half a dozen rifles with us, chambered between .223 and .300. Normally the rifles are used for different tasks, that’s the idea. But things never really work out like that.
For example, you can shoot a deer at 500m with a .300 WSM, and at the sound of the shot the mob hidden in the gully directly below you scatter, and then stop to look back on the opposite spur, in the open. That might be an only 150m away, so you shoot as many of them as you can with the rifle in your hand. It’s not like you say oh hang on a minute, I’ll just go and get the .243. What I’m saying is that with like-for-like placement, the .300 knocks them over in exactly the same way as the .243, 6.5 Creedmoor, 7mm-08, whatever the guy next to you is using. You only start
seeing the additional power of the magnum in the animal’s reaction at much much longer range than 300m. And that’s usually because at range, the higher velocity, heavier bullet, and higher ballistic coefficient, make it easier to put that bullet into the bang flop spot than it would with a lighter slower bullet that will struggle with the wind.
The OP asked his question into different ways, which can be interpreted quite differently. He used the words “capable” in the title and “comparable” in the text, and he specifically referenced a maximum range of 300m and only with respect to British game.
I know from a shed load of experience on exactly the same game that if I point a 6.5 Creedmoor at the shoulder of a red deer within 300m, it is going to fall over in precisely the same manner that it will if I shoot it in the same spot with a 7mm Remington Magnum. That is unequivocal. The idea that the additional power of the 7mm Rem Mag will magically knock the deer over more emphatically is a myth. I imagine some kind of cheesy Hollywood scene where the deer is hit by the Magnum and thrown 20m backwards. What was that film where the Ranger was using hand loaded .45-70 Govt and the bad guys were flying backwards left right and centre? Well it doesn’t happen with deer, does it. Shoot the animal in a bang-flop spot like the high shoulder, the hilar or the base of the neck, it will go down instantly. There’s a bottomless pit of videos on YouTube of guys shooting large, heavy feral hogs with .223 Rem in AR-15s, be it at night with thermal or from helicopters. Watch those videos and then watch the guys doing the same thing with AR-10s. With a competent shooter you will be extremely hard pressed to tell the difference.
Recently, one of our SD members kindly sent me an excellent video of an acquaintance shooting a proper large lowland red stag with a .243 Winchester. I can’t remember off the top of my head what the range was but it was something like 300m. He followed what I regard as best practice point of aim, the animal dropped like it had been struck by Mjölnir. I could’ve shot that exact same animal in the exact same way with my .300 WSM, the reaction would’ve been exactly the same. I’ll bet that if you didn’t know what cartridge had been used, some of you would have assumed it must have been a Magnum.
So you can make your own mind up between the two different interpretations. Similarly capable within 300m? Absolutely, without question. Comparable? Absolutely, without question. Within 300m, if you are a competent shooter, shooting medium game, then you should not be seeing any difference at all. You can’t get any more emphatic than in the video I just mentioned, or the videos I posted on here a few years ago of me shooting deer with 6.5 Creedmoor a lot further out than 300m.
This question is at the very root of “how much is too much?” when it comes to cartridge power for use on light framed, thin-skinned medium game. My view will never change, that being that a lot of European deerstalkers are over-gunned for what they are chasing, and that too much power often negatively affects accuracy. It’s a myth that a much more powerful cartridge automatically translates to more “emphatic” killing at relatively short range. Unfortunately quite a lot of us have the direct experience of watching those with powerful rifles adopt the questionable tradition of shooting behind the shoulder, and consequently demonstrate how easy it is for traditional stalker + over-powered rifle to lose deer, often at surprisingly short range.
This is already longer than I expected but I will just add one last thing. In recent times I’ve come to really enjoy shooting large deer with slower, heavier, wider bullets, e.g. 220gr round nose SPs in .308 Win or 280gr HPs in .44 Rem Mag. Adopt the normal point of aim and the killing is spectacular but without the attendant tissue damage. There’s an awful lot to be said for re-visiting the old timers’ methods, but with modern weapons, binos, rangefinders and so on.