Ok, latest info as of this morning, (8/8/18) I spoke with MVB after ordering one of their stocks and finding that the CMMG Guard .45 bolt would not retract far enough into the stock to properly cycle, that the issue is probably the buffer. In the early days of the Guard and Banshee MVB apparently got the impression the weight that can be added to the Banshee BCG for suppressor use, was a needed component for the action to function. They concluded their buffer, which embeds into the back of the bcg prevented the it from cycling properly. Which I learned that it does in fact do this.
So I spoke with CMMG and with MVB and this is the conclusion we came to; If you use the MVB ARC stock with the CMMG Radial Blowback system, use the [b]standard AR spring and standard AR buffer for the 9mm, the standard AR spring and H1 buffer for the .45. RIFLE buffer, not PCC buffers that MVB has listed on their sight.
Now, MVB is aware of this error in their understanding of the system, and are going to test this to make sure it is in fact compatible. I am also doing my own testing as soon as I get the correct buffers in hand on both the 9mm and 45acp to see if we are all correct that the RIFLE buffers will correct the functioning issues and be able to use this excellent PDW stock on these little beasts. Again, stay tuned........