This is actually a very easy question. Least ways seems to be.
First you find out what calibers holds the 1000 yard record for conventional prone shooting. Last three times it was set was done with 300 Win Mag. What calibers win the Wimbledon/Leech with regular efficiency? 6.5/284.
Next what caliber was outlawed in the Palma Trophy Match at Camp Perry after it won two consecutive years running. 30.06
What caliber holds the Palma Trophy Match record with a possible score? 308.
For closer ranges what caliber holds the 100 shot course records 200-600 yards and what caliber held it for 40 years?(answer coming) What caliber replaced it? 260 Rem.
What caliber held the 80 Shot Regional Course Record? 223 and I think 6MM Tubb? What caliber broke it this year? 260 Remington. Note: the 80 shot and 100 shot records are held by the same little young lady.

What caliber was damn close to taking it. 308 almost took it fired by Gary Anderson in 70s.

For 300 Meter shooting what is the most popular winning calibers
6 PPC and 6BR.
Performance counts, opinions are just opinions. If it doesn't hold records and doesn't win consistantly then............

If you want to compete in NRA competition and only buy one rifle it needs to be 308 Win caliber. This will get you to 1000 in all catagories. Any rifle irons and scope, match rifle and Palma Rifle.
If I were building a 1000 yard rifle today it would be 6.5/284.first choice, 30.06 second choice and 300 Win Mag third choice followed by 30/338 Mag and 7MM Rem Mag. Might even consider 7.5 Swiss but bolt face could be a problem, maybe not though.

There is no one caliber that is going to make you a winner without reliable fire control devices, load technique, barrel quality and most importantly skill from experience.

Shooting is like the NASCAR circuit. If Ford wins, folks buy Fords thinking they are fast but if you take a close looksee of a NASCAR set us there is no semblance of what you see inside as compared to the showroom. Last I heard the only factory thing many of them had was the hood.
The engine surely isn't, the fuel isn't, tranny is not, nor the rear end, springs, suspension etc. The motor oil in many is Mobil 1 and there is 80 quarts of that in the tank.
If I were you I would get a 308 and that will make you dangerous to 1000 yards and not worry about anything else right now.

To really explore this we need a definition of long range, accuracy requirements and terminal performance needed.

I shoot my 243 AI with 80 gr. FB bullets past 800 yds. on Rochchucks, my mile gun is a 338 Lapua Imp shooting 300's. I hold the NBRSA Heavy gun 1K yd small group record shooting FB 187 gr. 30 cal. That bullet also holds the IBS Hvy Gun small grouprecord. A very accurate bullet but not what I would use if I was out playing in the sand box.

What is long range?

Short range 400 yds. and in?
Intermediate 400-800yds ?
Long range 800- 1200 yds ?
Extreme long range past 1000 yds.



I have over 140 chamber reamers here and I get requests all the time for off the wall chamberings. I ask the customer to pick a bullet and speed and I'll tell them the reamers I have that will meet their requirements. Almost to a customer they will pick one I have already over reinventing the wheel.

Here's your questions that need to be answered in this order.
Pick your distance, look at accurate bullets availalbe with a BC high enough to get the job done, decide on the velocity needed, look for good quality brass then pick your cartridge.

25-20 sucks at LR

If the 6.5/,284 is that good (I used to have a .284 Ruger), I wonder what a 6.5/WSM could do?? And what's with the 6.5 Lapua ??

Of course, all mentioned are excellent, but somebody's always working on something new.

probably not 7.62x54r

Think bullet/twist/chambering/bbl length, roughly in that order.

Lot's of good LR bullets in 6mm, 6.5mm, 7mm, .308", .338". Just make sure you have the barrel twisted to accomodate the high BC bullets.

.257" and .277" are a little thin on LR bullet choices.