A couple of small points.
While congress has the authority to call forth the militia, it does not create the militia, which already exists.
Further court decisions will be required to make sense out of which firearms are "in common use". Certainly, the AR-10/15 series, AK/SKS series, HK-G series semi-auto rifles are in common use, as are the Barrett .50 rifles. But are M1928 Thompsons? Uzi and Ingram SMGs? How about .30 and .50 caliber Browning MGs?
I would suggest these are "in common use" but also limited use due to current restrictions and the cost of the firearms and ammo. One could argue either way with the M-14 rifle since few were ever sold as surplus. But there is no doubt they would be in common use if they were made available as surplus rifles like the M1 Garand.
I wouldn't be ardent in interpreting "in common use" to instead mean "in common use amongst civilians". Various iterations of select fire rifle have been in common use for decades. Is there a rifle more commonly used than the M16 in all its forms?