400yds isn't nearly as "far" Today...as it was 20yrs or more ago. Mainly because you can KNOW the distance and NOTHING will up connect percentages,in similar fashion as known distance and good boolits. 400yds+++++ is short action territory. Hint. Handy/dandy trumps all. Re-hint.

Now of course Today,Critters don't die any differently than they ever have,but reliably Dealing Death has never been so [bleep] easy. Again,due mainly to known distance. Hint.

I'd simply choose a boolit first and give it a thunk,in how I wanted to launch it. That thunk would include twist,throat,S/S spout(as a minimum),a synthetic handle,good mounts,good glass and a buncha trigger time. All of which is easily arranged and if you wasn't careful,you could have a GREAT [bleep] time doing it. A good LRF being a given. Hint.

I'd skirt 25's and 8mm's,due boolits,if only because there are vastly superior results available in other diameters,for like or less recoil. Hint.

Practice cain't be purchased and everyone is concocting reasons/ways to circumvent that portion of the equation,which is the BEST part of The Rifle,which I'll never [bleep] understand.

As a worst case scenario...noone hates 308's more than I,but I could take a newb with a NIB Montucky chambered same,set a 6x42 wearing M1 ele atop it in LW's,feed it good ammo(Skinners) and shoot cleans on 400yd clay birds until bored with doing same. That'd be aboutta #2 on the ascending Relative "Difficulty" Scale,with pouring coffee being a #1. Hint. That factoring a coupla minutes to ascertain correct assembly and tweak the trigger. Re-hint.

A guy makes his own "luck" and schit will reliably be as easy as you make it. Hint.

Cracks me up,how reliably stupid,people do schit.

Headed out to play with a new fast twist 243AI.(grin)