Do I just ignore the manual and start loading hotter? Obviously that's what Winchester has done with their factory loads...
You can ignore all the data in all the books if you want ... just please let me know if you do so I can avoid beign at the range that day ... watching a gun explode in someone's hands is not my idea of a good time.
Not neccessarily what Winchester has done. Typically, they would be testing their loads with a barrel & chamber that is "perfect" for that round.
Also, you (me, or anyone else) have no idea what powder they are using, which primers, etc.. They are also using Non-Fired Brass.
There are so many subtle differences when it comes to reloading that comparing the same "recipe" between two people with different guns of the same caliber will usually generate very noticable differences. A few thousands difference in seating depth, case sizing & trimming, etc can all play a factor.
Also, 40 Yards is really only usefull to see if a scope is hitting the paper. If you want to develop a load for your gun, you need to start at 100, then in the case of your rifle, stretch that out to 200 after you find something you like at 100.
It's fine to say 'don't exceed the manual' but that begs the question: which manual!?
Doesn't matter

Pick a manual you like and go with it. Just remember that 30 or 40 years ago, testing and measuring methods were nowhere near as technical as they are today - for all we know some of those older books have loads listed that may actually be a grain or two higher than what newer metalurgy & pressure testing deems safe. It's your gun, in your hands ... only you can determine what you are willing to do (experiment) with it.
If I'm developing a load, I'll check a few manuals, then take the average Max Load for the powder of my choice. I'll then usually back it down a fair bit.
In your case (two max loads shown at 46 & 49), I'd pick 47.5 as a "practical max" with 49 as a "full max".
From there, I'd probably start at about 42.5 grains, and load 3 of those, then 3 at 43, 3 @ 43.5, etc.. up to 47.5. IF the range is a long ways away, I'd load up to the 49 grain limit just to have them with me.
From there, start shooting @ 100 yards ... When developing, I like to leave at least a minute or two between shots with the chamber open. I watch each group for tightness and whatnot, and inspect the brass for any unusual signs.
IF I find a spot that seem to get a tight group (ex: 46.5) and then as I continue up to my "pratical max" load and see the groups expanding again, I'll skip even firing the > max loads and just pull them and reload them at home later.
After that, for a gun in your caliber, it's time to stretch it's legs ... if 46.5 was the tightest at 100, I'll load up a few at 46, 46.2, 46.5, 46.7 & 47 and try those at 200 Yards.
For each day out with your test loads, I'd also suggest ensuring you are using "equal" brass each time as well ... avoid mixing once, twice and higher fired brass in the same "development" shoot. And dont' check a few for neck size, case stretch, etc ... what you do to one, you need to do to all ... this is a science, and the attention to detail si what will get you to a result that will be well worth the effort you put into it.
And of course, you really want to do all of this on days with zero wind ... no sense confusing the matter
A lot of this is what I consider "basic common sense" as it is pretty much the first of what I was taught by my uncle when I was introduced to reloading 25 years ago ... I only repeat it now because I tend to worry when people openly question the validity of exceeding "published limits". Unless you have years of expereince at loading and know exactly what to look for (which I doubt since you named yourself a Newbie), I'd suggest that the "book limit" (of whichever book you chose to use) should be considered "Law" if you want to come home with all your fingers attached.
Good luck! Happy Loading! Hoep you find a load that works for your gun.