>>14582075You would need to redesign the bolt and receiver to take a bolt carrier. Then you'd need to add a gas piston assembly to the barrel with either a 1 piece bolt carrier / piston unit like in an AK or a spring loaded piston / separate op rod and bolt carrier unit like in an FN FAL. Put a spring behind the bolt to push it forward after cycling. Then you'd need to tune the gas system and spring to actually work correctly and not jam or send the bolt through your skull. Operation would be like a giant AK if long stroke piston. I can't think of any short stroke gas piston guns with rotating bolts right now. Then you'd need to cut a hole in the bottom of the receiver for a magazine and cut a ramp into the barrel extension for smooth loading.
What I'm saying is, you would be designing and building a new gun from scratch. I don't even know if you could build a gas operated .50 BMG rifle. All of the designs I know of use long recoil actions, and I can only imagine that there's a reason for this.