Welcome back to a most enjoyable sport.
What were you shooting before? Where?
Things have certainly progressed especially in the last 5 to 7 yrs. The smallbores (6mm to 7mm) have really come into their own. The 22cal has taken over service rifle classes but don't do as well beyond the 1000yd/m.
1000yd/m match shooting is being dominated in the light classes by the 6mm and 6.5. In the heavy classes, the 30 and 338 are still doing well but the 7mm is quickly making inroads.
I can only assume that you are paper punching or rock busting. In which case, the fast 6.5's and 7mm are really the best bang for the buck today.
The 6.5-284 is a nice base and will get the 142gr MK, 140gr Amax/SST's to 3000fps. This is all you need to shoot to a mile and beyond. Ballistically, right up there with the big 338's and 50's but at 1/2 to 1/10 the costs.
The 7mm is my present favorite and am shooting 2 7RM's and 162gr Amax. This bullet offers fantastic ballistics for dirt cheap and is readily available in Canada (a big consideration given export limitations from the US). Other very nice cases are the 280AI family, and the 7WSM. In a long enough barrel, easily get these bullets to 3000fps and beyond. The STW and RUM are nice but a bit big for this bullet weight.
At 3150fps, the 7mm Amax is the lowest wind drifting bullet I have ever shot and plenty accurate to 1000m. There will be little issue shooting this bullet well past the mile.
Right now Wildcat bullets (Canadian too YEAH!!!) is on the cutting edge for extremely high BC bullets and has recently released a 200gr VLD 7mm bullet. Based on shooting and comparing ballistics, this bullet has the highest BC of any bullet except for a couple of VLD match 50cal bullets.
Build a 7RUM and a 30" barrel and this rig will easily go 3100 to 3200fps. There is nothing that will come close ballistically. That includes the 50BMG and the enigmatic 408 Chey Tac.
LR development is and has always been driven by bullet development. The new bullets are in smaller cals and really push the ballistics envelop.
Of course, just about anything can make the trip. The 243 with new heavy VLD bullets will and so will the 308 and 155gr Amax (I have shot this to 1500yds already with excellent results). Of course, wind drift is higher but doping is half the fun.
The biggies like the 30, 338, 40 and 50 are excellent too but finding components in Canada is becoming limited and the costs are staggering if you shoot any volume. Also, there are increasing difficulties importing certain cals and components from the US. This makes cals like the 40 and 50 more problematic and again raises costs.
If you want the cutting edge, the big case 7mm and these wildcat bullets are it. You can most certainly have lots of fun with 'lesser' combos like the 162gr Amax and suitable case. Up to you.
Other sites worth visiting is
www.longrangehunting.com and
www.benchrestcentral.com. Here you can see discussions on some really big iron used for long and extreme range hunting and match shooting. This combines both ballistic performance and horsepower for solid effect on game.
Optics have many many options with quality scopes from dirt cheap to second mortgage. There are numerous products discussed but certainly post your questions.
Many production rifles are so accurate out of the box that they perform as well as custom magnums of 20yrs ago. Custom accurate rifles are simply astounding in what they can do.
The scope of these two topics is enormous so do some research on this and LRH site. Just about any question can be answered.
Enjoy...
Jerry