could I just run my latest idea by you guys

...I only want to know if it's feasible. Firstly, The rifle has one of my cartridges which happens to be a magnum .20....case is as wide as 762 x51.

Anyway it's a 20 round clip but there are 2 mags joined together...literally like a jungle style mag but they are just welded together....both ends facing up.

Anyway the rifle just fires the 20rounds and then you move the mag to the left to fire the next lot. 

The SAW has two barrels side by side.  When you insert the dual magazine, the left mag feeds the left barrel and the right mag feeds the right barrel.

Therefore, unlike the rifle, your SAW has 40 continuous shots. A 60s prototype AK managed this.

Ignoring whether it's a good idea, do you think it's feasible.

laterally joined/shiftable double and even triple mags are a very old idea, dating back to at least 1935. See Hyde M1935 SMG for example

That way your "spare" mag is always open for elements and can be easily clogged by snow/ice/dirt/sand/whatever while you shooting from your '1st half'

Double barrel SAW is even worse idea IMHO. You have almost double weight for 2 barrels and 2 bolt groups, you have an extra synchro gear, and you need to ensure POI alignment for two barrels, which is a major PITA in itself.