The M2 is inertia and the M4 is gas operated.
Inertia
Gas
https://www.benellile.com/argo
Interested as well.
"Improvise, Adapt, Overcome"
Not sure about linking to other sites, but the Canadaguns subreddit had someone do a pretty decent review of the CA612 and Canuck Operator. End result was that the CA612 looks to be a "clone-correct" copy of the M4 (no word on major parts fitting, but said it fit all the S&J Hardware upgrade parts) and had no issues cycling a variety of ammo.
No problem linking to information about guns on this site, some hot links and links to non sponsers selling products that sponsors sell are frowned upon but sharing information about guns is sort of what CGN is.
If you go in the advanced setting you can de select the option to hot link and that way the entire link can be copied and pasted into a browser window without subtracting or adding missing parts... if you can't figure that out post the link in a broken format of your choosing.
Our Government trusts rivets more then law abiding gun owners.