If I buy one of the brand rifles I mentioned earlier, how would I add extra free bore? Or do I need to do a custom build?
I'm pretty new to all this. I ve only been shooting and hunting for about 18 months but I am reloading. I live in Florida so this firepower is over kill for down here. This would be a once a year hunting trip if things go well so I'm trying not to over complicate things. I don't expect to take a shot over 500 yds but on the other hand I d hate to limit myself. One thing I m certain of is that 300 win or WSM or prc is about as much recoil as I'm interested in "enjoying".
Although I love the idea of custom rifles, there are many "off the shelf" rifles available today that give you all the accuracy you need to shoot 700 yards with a 300 WM or 300 Weatherby. I've never shot a Sako that wasn't accurate enough for a 700 yard shot — if the shooter was up to it. Browning & Savage rifles also tend to be VERY accurate out of the box.
Recoil is much more than a function of cartridge. The weight, length, and configuration of the stock have HUGE impact on felt recoil. I have a Rem SPS stainless in .270 WSM that kicks harder (felt recoil) than my .300 Weatherby or even my .338/.378 Weatherby. That .270WSM will get a brake. If you don't like recoil, or have a chance to shoot enough to learn to handle it well, DO NOT buy an ultra-light "mountain rifle" — unless you are going to be hunting mountain goats in the near future.
.300 Win., .300 Weatherby, and .338 Win don't kick hard in full sized rifles. The only time they are at all "punishing" is in LIGHT rifles, especially when practicing on a bench. (I can't speak to .300 WSM as I've never shot one, but it should be very similar.)
You didn't mention your financial situation, so it's hard for me to recommend new or used rifles, but I bought most of my firearms used — and saved a fortune! It's worth considering. I do recommend shooting others' rifles before you make this decision. You may change directions abruptly once you try a few different rifles. If you lived closer I would offer you some range time. When I lived in Florida I found ranges to shoot at. People at those ranges should be able to loan you guns to fire a few rounds through so you know what each feels like.
Good luck!