have watched videos from professional long distance shooters and they always recommend shooting the heavier bullets and a barrel with twists to handle heavier bullets.
Recommending heavier bullets is an over simplification and not really accurate. When shooting beyond about 200 yards the bullets aerodynamics come into play. Within the same caliber longer bullets will be more aerodynamic. Within the same caliber longer is heavier. But not always.
Bullets aerodynamics are measured by their ballistic coefficient. BC.
A round nose 180 gr 30 caliber bullet has a BC of only .241. Some of the high BC 180 gr bullets have a BC around .535. If we shoot both of those from a 30-06 @ 2800 fps the high BC bullet has a huge edge. At only 200 yards it drops 1 inch less and has a 700 ft lb advantage.
At 500 yards the high BC bullet drops over 2 feet less and has over 1000 ft lbs more energy.
This is why cartridges like the 6.5 Creedmoor are becoming so popular. Their best bullets are near the .7 BC range and can be fired at reasonable speeds. To get a 30 caliber bullet with a BC in the same range it would have to weigh 215 gr or more and would need to be fired in a 300 magnum to shoot it fast enough to be useful.
I just have heard of some bullets tighten up at distance and some groups widen at distance.
A hotly debated internet topic. I've observed instances where a rifle would do no better than 1" groups at 100 yards. Logic says that rifle should do no better than 2" at 200 yards, 3" at 300 yards and 4" at 400 yards etc.
But I've seen those same rifles that shoot 1" at 100 yards shoot 1.75" at 200, 2.5" at 300 and 3" at 400 yards. Group size isn't smaller, but the MOA is. There are lots of other guys who have observed the same. Not with every rifle and load. But with specific rifles I've seen it happen.
WHY this happens is the debate. There are lots of theories, and a camp of that says it is either coincidence, or that the shooter is just aiming more precisely at longer ranges.
I don't know the answer. Just reporting that I've observed this when shooting some specific rifles. If it is coincidence, or if I'm aiming more carefully at long range then why does it happen only with certain rifles?