The Stoner 63A weapons system made by Cadillac Gage in Warren Michigan. It, as far as I know, is the only fully intergrated weapon "system" ever devised or fielded in the terms of "small arms". While not perfect or without issues, it was very successfully fielded by navy SEAL Teams in the Vietnam conflict. Unlike most corporations, Cadillac Gage was VERY keen on updating the system whenver the general consenuses of field operators deemed it necessary. the Stoner went through a large number of imrovements, fixes and changes based on SEAL Team input. Sadly, the United States Army and Marine Corps. didn't see the potential of such a system and it eventually faded away into legend.
Robinson Armament based the M96 rifle on the Stoner 63 but they abondoned the proper operating rod carrier setup for a very complex ( though effective ) setup that did not improve upon the Stoner design at ALL. So, despite the fact that RA improved upon the Stoner 63 bolt carrier they took two steps back when creating the op-rod carrier interface. Not to mention, RA has done NOTHING with the M96 to make it anywhere near as interesting or multipurposeful as the Stoner 63. A fine gun....but there is nothing about it that makes it any better than an AR-15 if you balance everything out.
Back to the Stoner:
a Stoner 63 could be reconfigured into the following weapons by simply stripping the gun down to it's main chassis and adding the correct components:
1.Standard Closed Bolt Assault Rifle ( select fire )
2.Same as above: Carbine
Both versions of the rifle concept used a very nifty full profile folding stcok that folded to the side ala the AR-18.
3.Open Bolt Top Magazine Fed Light magaine gun.
Think 5.56mm Bren Gun.
4. Open bolt belt fed LMG, standard length standard left side feed.
5. Same as above with Right hand feed.
6. & 7. Same as above with Carbine length barrel.
8. & 9. Same as above with short Commando length barrel
10. Solenoid triggered, mounted light machine gun with feed chute and large box magazine.
11. though not manufactured this system could, with the additon of match trigger, target barrel, cheek piece and optics/mount could have further been developed as what we now call a DMR.
All of that with a common chassis, ambidexterous operation of both the safety and the chargin handle............................imagine the logistical simplicity.....no wonder the military dropped it.
Oh, I forgot: #12. Tripod mounted LMG.