185gr vld Berger's is what it does it with. Can I realistically get there to 2km? If so, then I've been grossly misinformed.
Dead seriously, if this is realistic then I've overlooked something along the way and would be happy to push my gun that far.
Upgrade barrel twist to push 215 and 230 bullets and done?
I have had the pleasure and privilege to shoot very far for many years. I have built many boomers as well as other more competition focused rigs. I have helped a number of shooters fulfill their dreams in all manner of goals... but when it comes to 'want to shoot out to 2000m'... the first and most important question is
Where do you live or have access to? Many populated places in Canada have some real logistical problems when trying to reach out that far.
If this is a once a year/lifetime type trip, then consider the distances you can access often and build something that makes this as challenging.
I am now mucking about with rimfire at distance and I can say that getting the set up right to hit a reasonable sized target out to 500yds with a 22lr is a hoot. A few brave souls are trying to reach 1000yds reliably.... not my cup of tea but you want to learn all about ELR ballistics and wind and weather?
On a more accessible note, a mid sized 6.5 case will easily reach out to a mile.... and if you are like 90% of the shooters, your one gun will spend more time inside 1000yds then beyond. You aren't going to learn unless you put lead downrange... 1000rds isn't alot of shooting if you are truly interested in mastering LR shooting... so think of this journey in terms of BARRELS.
For plinking, I really enjoy my 22 Creedmoor and inside 1500yds, shoots great. for 1 mile, the good ole 308Win set up for FTR type bullets .... the combo can go alot further but the spot we venture to most often is best suited to the mile. And yes, I do shoot with those that use boomers including a 408CT (sigh, change the damn laws back).
Shooters have been shooting 6BR's to 1 mile for years. I did take a 223 Rem to 1 mile many years back... definitely not my choice today but that same set up had to no issue going hit for hit with a 338 Lapua to 1400yds.
The 284 Win can shoot ridiculously well at 1000yds... we know the bullets can easily reach 1 mile.
Your lowly 300WM has reached distance much further then your goals... and I have little doubt that 185gr VLD will make the trip. If not, just load some new gen Sierra 200grs or Berger 200-20Xs and hit 1 mile and beyond easily. Talk to those that have real world experience... ballistic app gurus may not understand what is actually going to happen downrange.
If you have a game or want to break something way out there, then by all means, build the horsepower to make the trip 'boring'. If you just want to have accurate fun way the heck out there, this is more a bullet question then a cartridge question.
To put things in perspective, each 150fps is around 100yds of addn ELR distance before things hit the wall... if they are going to hit the wall. compare the ballistics of a Berger 200-20X (BC data very well sorted) at 2600fps, 2800fps, 3000fps wrt to drop and most importantly DRIFT.
by all means, if a boomer is what you want, build it... but I would worry about finding components, dies, powder long before you worry about what action you want to use.
YMMV
Jerry