.300 Win Mag. Wouldn't that be a bit too much on smaller game like roe? Even 30-06 has occasionally been too much (although, it seems 150g is strangely sometimes worse on meat than 165 or 180, but I guess it depends on what the bullet has struck). And it mostly gives you more range? So, for mountain and plain hunting?
That's why I would want the first rifle to be slightly weaker than the 30-06 (which I think is perfect for midsize deer to moose, but overkill on smaller game, like beaver, fox, roe, lynx etc, especially when using 180grain, and I would like to stick to one load, call me lazy). The second rifle should have only overlap on the medium spectrum of the hunted game, which means they could be used as backup for each other for certain game). I think the 30-06 is as such also a perfect backup caliber, I mean it can probably do everything from foxing to elephant, but it's not ideal for those extremes exactly (nor legal on the upper end).
400H&H looks really cool. Had never heard of it though and have never seen a rifle for it either. I guess it could be hard to get ammo for it as well.
Although I would rather just buy the 2 right rifles from start I have a feeling that I'll go for two CZ 550s in different calibers and later when I can afford it upgrade the second rifle to a double.
Slower bullets tend to destroy less meat. When I shoot something with my 45-70, pushing 425 gr or 525 gr bullets along at around 1600 fps, it's a rare day when I end up with more than a few ounces of ruined, blood-shot meat. Often, I can eat right up to the hole.
This is what high speed, coupled with thin-jacketed bullets does (300 PRC firing 212 gr Hornady, 200 yards to target). I wish I had a pic of the other side, I'm guessing there's probably not even an exit wound.
You will find vast expertise and experience here in this forum. Most of the dudes here who shoot fast movers have a good reason - it usually involves shooting a great distance (further than 300 yards), and they're all good enough to make those long shots. Or alternately, the shots may be nearer, but to a man, they're all shooting premiums like A Frame or TSX or similar.
If you wanted to go with a single rifle, it would be difficult to beat 375H&H/375 Ruger or 9.3x62. With the right ammo and the right game specie in your scope, you can stretch the 375s to probably 500 yards. You could stretch a 9.3x62 that far as well, but it has about the same ballistic arc as a 308 Win firing 180 gr bullets - not horrible, but also non-trivial.
The one challenge with 375/9.3 as a 1-gun solution is recoil. Neither are horrible, but can be daunting for someone with little shooting experience.
For a long range *hunting* gun, it's hard to beat 7mm RM/280AI or 300 Win Mag. I favor heavy-for-caliber in everything I own - 160 gr or 175 gr for 7mm bullets; and 200 - 220 gr for 30 cal bullets. Velocity gets a bullet to its target, but it's bullet mass that gets a bullet through the vitals. Heavier bullets with their higher sectional densities will out-penetrate (and usually ruin less meat) lighter bullets in almost all circumstances. Additionally, heavier bullets will also have higher ballistic coefficients than lighter bullets of the same caliber/construction, so their ballistic arcs tend to be flatter once you get past 300 yards. This translates to higher velocity (usually) past 300 yards. So you have a faster, more massive bullet to do the work of getting through the vitals.
I'd like a 450/400 or 470 NE as much as anyone, but because of the way barrels are regulated on SxS double rifles, I imagine accurately shooting past about 150 yards can be quite the challenge.
For the 416 and 423 cal bolt rifles, there are lightweight bullet options somewhere above 300 gr and lighter than 400 grains that can extend your reach. This becomes my exception area for favoring heavy-for-caliber. A 300 gr 416 or 423 bullet scooting along at 2700 fps will get you out to 300 yards fairly nicely. And there are a bunch of good choices in 458 cal bullets that are lighter than 500 grains. I'd still favor 400 gr in the "small" 40s and 500 gr in 458 for hunting cape buffalo or hippo.
