There are a few complications that would arise from designing this project for a larger caliber. By and large, the charging handle location (in-game) is the biggest blocker. It lies directly where an AR-15 gas tube would go.
Additionally, most bufferless AR designs are a bit longer that would fit in the exact footprint of the current geometry.
- Remove the "Front" from the "Back" but sliding the handguard off the 2020 extrusion. You may need to unscrew the bolt opposite the safety.
- Take the stock off
- Use an allen key to unscrew the 4x bolts on the back of the BCG
- Remove the rear takedown pin
- A this point, you should be able to rotate the upper receiver forwards a few degrees to slide the BCG out the back. You won't have access to the trigger assembly unless you take the side plates off.
- Sliding the BCG backwards will arm the trigger. Don't release the hammer or you'll have to awkwardly re-cock the hammer to get the BCG back in.
Because the MA40 is absolutely the sexiest variant of any of the MA series rifles.