I have a RDIAS and am looking for different ways to utilize it beyond the standard AR upper/lower combinations. A recent discussion here (that got nuked) got me thinking about belt-fed, which sent my mind wandering. I know getting some hosts set up to run good are more involved than others....But does anybody have any suggestions for some fun alternative hosts? I appreciate any input you may have.

You mean like a MCR for beltfed or a Ceiner 22lr upper. Maybe a 9mm host, but you might need a mod to fit the DIAS properly.

Yes, I got interested in a "high cut" nutsack lower for an MCR upper. Seems like a better solution than the standard mounting on an M16.

As a RDIAS owner, IMHO the MGI modular lower is the ultimate.
My Shrike/MCR magwell directly accepts SAW nutsacks/porkchops and still accepts mags/drums but I don't like how thin it is.  I bought a chunk of aluminum to make another magwell that is fatter to has more surface area to engage the SAW boxes and still accepts mags but I will probably make it wider so it won't take a Beta Mag but I could care less about accepting a Beta mag.
I also have the belt fed 9mm FM9 and I think I'll just use the same magwell for 9mm but will have to mod a block for the fixed ejector that normally goes in the magwell.


I also want to make a magwell to take .308 DPMS G2 magwell and one for Scorpion mags for the curved MP5 look but with LRBHO for use with my CMMG RDB or MEAN Arms bearing delay if it ever comes out and works.

The MGI lower looks outstanding. Anywhere to currently buy the lower and all the magwells, etc?

There are several on Gunbroker right now.
Windham Weaponry bought out the rights to the system but they haven't done anything with it...shame...
https://www.windhamweaponry.com/firearms/rifles/mutli-caliber-systems/
Note that TMK, they will only sell complete guns or the magwell kits.  They won't sell just the back half.
MGI used to sell it for $99 then charge like $250 per magwell.

They only have the regular AR15 magwell, Colt 9mm pattern but using a block and the AK.47 magwell.
Note that TMK, they will only sell complete guns or the magwell kits.  They won't sell just the back half.
MGI used to sell it for $99 then charge like $250 per magwell.

They don't have any of the other ones like I have in my picture above.  It has been several years and I doubt they are going to do anything with it either.  
I wish someone would breath some life back into this system.
BTW, I also have a small frame Glock magwell hoping it would work for my CMMG RDB but not only is the height off (which I can fix) but the angle is all wrong for the CMMG RDB.  
There is a complete rifle on GB now.
With so many different lowers out these days, I would think it would be attractive for even non-MG owners that want to SBR one lower and then have so many possibilities.

Also, I never cared for the MGI upper since there are no front sites I know of that are adjustable for windage and elevation other than the one for the MCR / Shrike.  So the whole barrel swap thing I think is a waste of time.  Just swap complete uppers (with optics mounted).
Now there are some optics that have programmable zero's.  That would make sense for quick change barrels but I'm not going to bother with that myself.

All that said, even with the lack of more magwells, if you already own a RDIAS, I would strongly recommend getting the MGI lower even with just what is out there.  The AK magwell is great and you can get a spare AR Magwell and cut it to take the SAW boxes and still take mags like I did.  
I prefer my 7.62x39 setups more than a real AK.  Much easier to tune and you can get them running smoother than you can an AK.
Poke around my website and you will see several pics of my setups.

https://c3junkie.com/

A friend of mine had a LR308 magwell for those lowers that he was doing final tweaks on. It ran about 75%. That was a couple years ago. I wouldn't be surprised if he has it running perfect now.

Like "amphibian " I too jumped on the MGI hydra system back in the day, for my DIAS. I don't have the small frame Glock or 5.45X39, but do have the large frame Glock, Grease Gun (used with the CMMG rotary delayed blowback in .45), I also had a custom built Thompson magwell based on the Colt 9mm system (used with a Ron Williams .45 DI upper), and a custom machined standard magwell for use with Valkyrie Armaments belt fed conversion (for use with custom water cooled or MGI modular upper with three piston modified Bushmaster 14.5" heavy fluted barrels.

I made myself crazy trying to get a Colt M16 registered receiver to run reliably in 9mm. The  drop in magwell would push up so that the ejector would rub the bottom of the bolt and make malfunctions. It wasn't until I got the DIAS and put it into a Colt 9mm carbine lower that I finally had reliable 9mm blowback. Had Garrison Manufacturing build me a DOE clone from their custom parts and a Colt upper. It is most likely The closest I will get to shooting a Colt 9mm subgun/DOE.

I missed the Russian 5.45X39 surplus. But I didn't miss the 7.62X25 surplus.  Ron Williams made me a 7.62X25 DI upper and PPS-43 magwell adapter. It is cheaper to shoot for me than CCI minimags at today's prices. These are just some highlights. What mechanism do you want to shoot? But be forewarned, it is not so much coming up with ideas. It is finding qualified people who have the skills and knowledge to build your dreams. If you do find them, they will tend to be so busy that it will be hard to set up a time for them to work on your project no matter what you offer.

So, what do you want to shoot?  The MGI modular lower is a good place to start.

Scott

I’ll second the high cut MCR lower as well as the colt
308 lower.