6.5x55
7x57
6.5x57....improved????

.222 Remington

It's hard to believe that it is "obscure", but there isn't much being chambered for it nowadays. Mine is an (old man) Hart barrel and it is by far the most accurate rifle I have ever owned. It's very much over-shadowed by the .223 now. Mine has taken several hundred p-dogs, a couple turkeys, several fox and coyotes, and one deer, (long story).

I have a Win. M64 in .25-35 that I really enjoy, indeed, occasionally use it to hunt (Pronhorn). 6.5x55 isn't too obscure, but mentioned several times, and I really like it--my sheep rifle. Lastly, one that I'm surprised hasn't been mentioned is the .404 Jeffery. I don't have that one at present, but will in due time, for sure. The .264 Win in a pre-64 M70 is another I will have when oppertunity presents itself.

The 6mm Rem. International is my favorite. I got one in the early 60's in a 40X and used it, with success, in position target matches at 200 yds. I still shoot that rifle but by now it's been rebarreled, to the same cartridge and has a thumbhole target stock. The cartridge was developed for 300 meter position matches but the military went with the 308 Win. instead. Also the cartridge missed out as the bench rest game ruled it out in the Hunter class.

Others are the 8-57 JR in a drilling and the 358 Win.

The 222 Rem was a favorite but I moved on to larger .224's with reduced and full loads.

I have a few that I hunt with almost reloading only.The 375 win in big bore 94 Winchester,The 264 Win Mag in Stainless Rugers very accurate,and in pistol both the 41 mag and the 32H&R mag in Ruger single sixes . I forgot the 357 maxium a round that thinks it is bigger than it is.
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6PPC

22PPC

Great rounds for target AND HUNTING.
If you have one, you can make up the brass for the other.
The 22PPC sits between the high velocity .22 and the lower speeders, making it, in my opinion just about perfect for a high volume shooting varmint rifle.

I have a 6PPC which gets used on everything from varmints(when I'm overseas) to wild boar.
I have a whole lot of other rifles that would "do the job better" or with a lot more grunt, but just about every time I'll take that one out(which is nearly every day).

I'd take just about anything with that rifle...through the head.

Unless I missed it, no one has mentioned my newest addition
35 Whelen Improved...
and like many, the 6.5x55

The 6.5 x 55 is THE best rifle cartridge ever invented for medum-sized game - and its been around since 1896! I've got one in an M98 that does just under 3000 fps with 140 gr Hornadys with no signs of pressure. Zeroed at 100 yd it doesn't drop an inch at 200! Its as close to a "death ray" as anyone could want. Why its "obscure" I have NO IDEA!

Just my very humble opinion and 2 centavos...

BTW I think the 35 Whelen is cool too, and combined with the Swede (unless Jurassic Park is real) you're equipped for anything in NA.