Nice way to kill our troops. The reliability of the system is already questionable....using uppers not designed for those lowers will simply lower the reliability.
We're talking sniper rifles here, not battlefield weapons.
M24 in .300 Win is OK, but still insufficient for extra long-range. That is why the Brits use the .338 Lapua for sniping and we use the .50 BMG for sniping.
I am very familiar with sniper systems ... Having shot expert my entire time in the Infantry and having been a designated marksman.
Someone familiar with the AR-15 / AR-10 receivers would have known that the lower receiver would have to be modified to meet this requirement. It was the concept of a swappable barrel that I was presenting.
I will also remind you that many battlefield weapons have been used as sniper weapons with modifications (M14, Galil, M1C/D, M44, etc). It is often not about how fast / far / big / hard hitting / accuracy etc..... Case in point, the .50 makes a great sniper weapon but it and it’s ammo and support systems are heavy. The Israelis have a .22LR sniper system that they use inside a city with sub sonic rounds and suppressors. Works great in close quarters.
And lastly, you seemed to have missed the point I was presenting in my post which was, just because it seems obvious (swappable barrels or going to a different caliber) it is not always so “obvious” to the troops on the ground for a number if different reasons.