that 'family' of rifles may be fairly decent hunting guns, where you fire a few shots a season, but they are NOT designed as battle rifles. They are very difficult to field strip for cleaning. The design is not all that sturdy, nor was it intended to be.
They have hard enough time not jamming with the regular mags, I would have a hard time seeing them functioning reliably with a 20 rd mag...........
I got some hilarious stories of my dad and the two years he carried a 742 elk hunting..........
Casey