10 round AR mags... Why not Kel Tec PLR mags??

[SCDL]

Ok so if the mag was designed for a PLR pistol and you ground of the rib I assume that it would be legal in the ar as it was designed for the PLR

You COULD modify the rifle's magwell to accommodate the mag, but I expect that's further than most are willing to go when we already have functional 10 round mags.

 

[acrashb]

You would have to cut a channel clean through the magwell up one side, radically weakening the receiver. Like you said, not worth it with existing pistol mag availability. maybe not even possible given the required surgery.

 

[lone-wolf]

the only rifles that are limited to 5 round capacity are semiauto centerfire

pump, lever and bolt guns have no capacity limits

Enfield magazines are specifically stated as having no capacity limit in the regulations.
Just saying cause you sounded like you didn't believe supernova's comment about the enfield.