08-04-2012, 06:13 PM
Another great upper is the LaRue Stealth. I do think it is prudent to go with a larger mass upper, with a tight-fitting barrel extension slot.
This is one of the areas that AA pays attention to with the heavy barreled uppers, machining tolerances so that tightness helps with a consistent barrel to receiver mate.
Keep in mind that the AR15 upper receiver was designed around the .222 Remington cartridge, with as lightweight barrels as possible, weight being the key factor in determining the construction. The .222 Rem is a 50,000 psi rated SAAMI cartridge.
When the AR15/.222 Rem couldn't penetrate a steel helmet at 500yds, they blew the shoulder forward, increasing powder volume and driving the pressures up to 55-58k psi, however, the bolt, barrel extension, receiver diameter, magazine-COAL relationship, and other parts associated with harnessing this pressure/barrel whip were not enlarged to even really create an ideal platform for the 5.56 NATO since it would have been so minimal in dimensional changes.
No take a cartridge with a larger case head diameter and try to pack it into this receiver set, hang a 24"+ heavy barrel off it, and expect ideal results....? This is why the beefier upper receivers make a lot of sense for this type of build.
This is one of the areas that AA pays attention to with the heavy barreled uppers, machining tolerances so that tightness helps with a consistent barrel to receiver mate.
Keep in mind that the AR15 upper receiver was designed around the .222 Remington cartridge, with as lightweight barrels as possible, weight being the key factor in determining the construction. The .222 Rem is a 50,000 psi rated SAAMI cartridge.
When the AR15/.222 Rem couldn't penetrate a steel helmet at 500yds, they blew the shoulder forward, increasing powder volume and driving the pressures up to 55-58k psi, however, the bolt, barrel extension, receiver diameter, magazine-COAL relationship, and other parts associated with harnessing this pressure/barrel whip were not enlarged to even really create an ideal platform for the 5.56 NATO since it would have been so minimal in dimensional changes.
No take a cartridge with a larger case head diameter and try to pack it into this receiver set, hang a 24"+ heavy barrel off it, and expect ideal results....? This is why the beefier upper receivers make a lot of sense for this type of build.