Inglis WWII Hi-Power with shoulder stock / holster…Qualify as short barreled rifle?

[whatnickname]

I occasionally see WWII Inglis Hi-Powers for sale on GB with wooden shoulder stocks that are attachable. Wouldn’t mind having one but I’m concerned that the use of such an attachment would qualify as a short barreled rifle. If in fact the ATF considers these short barreled rifles, could they be registered as a class III weapon? Assuming they could be registered as a class III SBR, any idea what the cost and time it might take to get approved?

 

[dogtown tom]

The Chinese Contract Inglis MkI is specifically "removed from the purview" of the NFA as a curio & relic.
Only the original stock design or a reproduction of that original design is acceptable. (FN made a "flat board" stock/holster that would not meet the "original" requirement on the Inglis.)

C&R List See page 23

Canadian Inglis No. 1, Chinese Contract, Hi-Power pistols, cal. 9mm Parabellum, having a
tangent rear sight adjustable from 50 to 500 meters, slotted for shoulder stock, and having the
letters CH in the S/N and accompanied by original Canadian mfd. detachable wooden
holster/shoulder stock