The reason for inquiring is that a Mk7 and Mk5 share the same barrel retaining system and mid casing barrel bushing.
It seems to "stand to reason" that if one had a Mk5 casing (perhaps damaged when installing the front or rear surpressor bearing surfaces) it would be simply a matter of removing the (damaged) front casing section and "viola" a Mk7 has appeared (assuming the stock trunnion isn't installed yet).
This is based around incomplete casings rather than returned from service or to the factory completed guns.