Paparock
Previously Rocky W.Latham
Of the cartridges you mentioned I would go with the 280AI with the ultra-premium bullet your rifle likes the best. I like the heavy for caliber but each to their own.
May I ask why you want a very lightweight rifle? The reason I ask is of all my friends that had them build found them great to carry but hard to shoot accurately under actual hunting conditions in the mountains. When chasing Elk or Mule Deer sometimes you have to move fast to get to a good shooting position and that is when those ultra-light rifles move with every heartbeat making those crosshairs dance. Personally I have always preferred a slightly muzzle heavy rifle as it helped me steady the rifle for such shots. This is where a great custom rifle builder comes in. Back in the stone age when Dale Story built my custom .375 H&H I was sort of unsure of such a big caliber as I had never shot anything bigger than a .30-06. Dale came into my wife's restaurant in Casper, Wyoming as a regular so I went to his shop and talked with him. He told me he hunted with a .375 H&H and not to worry as he world treat me right and boy did he. The rifle was built on a fiberglass stock, I don't recall the brand now, but it was so light I could hold it up with my right arm, aim and shoot it with very light recoil. He put his personal favorite muzzle brake that he said had the last series of holes slanted forward to lessen the muzzle blast. The recoil was like a .243 and was a dream even off sandbags at the range. If you told me I had to shoot 100 rounds of full power loads at the range I would have chosen it over my custom .30-06 it was such a pleasure to shoot. So if you pick the right custom gunsmith he can build you a rifle to fit you that makes a big difference in felt recoil (I'm 6' 5" and ape hanger arms). So you can pretty much pick whatever caliber you think fits your needs the best if you pick the right custom gun maker that takes the time to custom build the gun to fit you! I hope this helps you and wish you great success and joy in your hunting future! I know they are expensive but they are worth every penny when you get the right one.
Rocky
May I ask why you want a very lightweight rifle? The reason I ask is of all my friends that had them build found them great to carry but hard to shoot accurately under actual hunting conditions in the mountains. When chasing Elk or Mule Deer sometimes you have to move fast to get to a good shooting position and that is when those ultra-light rifles move with every heartbeat making those crosshairs dance. Personally I have always preferred a slightly muzzle heavy rifle as it helped me steady the rifle for such shots. This is where a great custom rifle builder comes in. Back in the stone age when Dale Story built my custom .375 H&H I was sort of unsure of such a big caliber as I had never shot anything bigger than a .30-06. Dale came into my wife's restaurant in Casper, Wyoming as a regular so I went to his shop and talked with him. He told me he hunted with a .375 H&H and not to worry as he world treat me right and boy did he. The rifle was built on a fiberglass stock, I don't recall the brand now, but it was so light I could hold it up with my right arm, aim and shoot it with very light recoil. He put his personal favorite muzzle brake that he said had the last series of holes slanted forward to lessen the muzzle blast. The recoil was like a .243 and was a dream even off sandbags at the range. If you told me I had to shoot 100 rounds of full power loads at the range I would have chosen it over my custom .30-06 it was such a pleasure to shoot. So if you pick the right custom gunsmith he can build you a rifle to fit you that makes a big difference in felt recoil (I'm 6' 5" and ape hanger arms). So you can pretty much pick whatever caliber you think fits your needs the best if you pick the right custom gun maker that takes the time to custom build the gun to fit you! I hope this helps you and wish you great success and joy in your hunting future! I know they are expensive but they are worth every penny when you get the right one.
Rocky