Why not????

[the Bamster]

Would an ar in the FN 5.7 be rockin for the sbr guys. One would think the mag would be the biggest expense. Is there patent issues? In 5.7 a 10.5 barrel would really start making sense. Any thoughts?

[Failure2Stop]

It's been done already.
The only thing the 5.7 makes sense for is to eradicate squirrels in body armor.

[parishioner]

http://m4carbine.net/showthread.php?t=19913

[the Bamster]

Hmmmm....... who woulduv thunk it. I would have thought it would have given 5.56 performance with less flash in a shorter barrel.

[orionz06]

the 5.7 round is really only valuable in the FN 5-7 pistol, where it is significantly smaller than other comparable alternatives (5.56 pistol), but again, the above link shows that ammo selection for the current pistol might be a better choice.