Ammo for .223 that is hunting worthy is far more expensive than anything soft point or hollow tipped in 762x39. I know, cuz I hunt with both. That being said (which you did, thank you) the capability of the 762 is superior to the .223 past 200 yards, and in the SKS or long-sighted AK, quite devastating.
Not so much when the .308 is thrown in. Good point.
For those suggesting KT sub 2ks: they have a checkered history of unreliability, experienced by myself, and if you suggest it, at least give opinions of what ammo function well in the rifle. By itself, it's not a really good choice, not compared to the 995ts.
The 223/5.56 has better range and flatter trajectory than the 7.62x39 or the 7.62x54. It's been found overall the 5.56 has better terminal performance than the 7.62x39 comparing FMJs. Terminal performance of the 308 beats the other three hands down.
I have found hunting ammo for the 223 at Cabella's in 100 round packs that costs less per round than most other calibers. (What surprised me is that 22-250 cam be had in 100 round packs for a decent price as well.)
A lot of 7.62x54 ammo is corrosive and I don't want to deal with that. Both the SKS and the Mosin are clumsy, crude and uncomfortable to shoot. Don't want any of that in a rifle I might have to trust my life to
Come right down to it, my $300 truck rifle would be used Remington 700, Ruger M77 or Winchester Model 70 in 223/5.56, 308 Winchester or 30-06. If I could find a sporterized 03-A3 in the right configuration in 30-06 within that price range, that's what I'd go with.
Since I can afford more than $300, truck rifle duty rotates between the M14, FAL and AR. They are sometimes accompanied by a 10/22 sporter or a Marlin lever action .22. But a $300 Remington, Ruger or Winchester is a good place to start