Too many people asking if X part will work in their Gen4 or if a Gen4 part will work in X gun. And feel free to correct me if I'm wrong on anything. So here we go....
Gen4 bolts are about 1/8" shorter than Gen3 bolts, so they will not work by just dropping them in. Some have put orings infront of their ram caps to compensate for this, but I would not reccomend it. Also, there are currently no aftermarket bolts out for Gen4s, but the Gen4 Hardshell bolt will be out soon. No reason to try and make a Gen4 bolt work in your Gen1/2/3, same thing just shorter.
Gen4 Ram sleeve is a lot shorter than previous versions, have the bit of metal sticking out at the back for the ram cap, and have the integrated poppit/valve, so they will not work in any other gen. No aftermarket parts yet, but rumor has it that there will be a kit to retro fit the Gen4 valve system on other gens. Don't take my word on this though.
Gen4 ram caps thread ONTO the body rather than INTO is, so no way no how it will work on anything else. Currently no aftermarket ram caps either, but really no reason for it.
Gen4s use the same LPR blocks as Gen3s.
All gen LPRs are interchangeable.
All Intimidator volumisers are interchangeable.
Nope, shorter than the other gens. No aftermarket parts out.
Currently the only aftermarket triggers that work in Gen4s are Gen4 Technas, the 05 CP triggers, and BL rollers. The reason for this is that there has to be a certain ammount of metal milled off the back for it to fit in the frame. However, all Gen4 triggers will work in previous gens.
Nope, just different. No aftermarket parts out.
All Gen3 boards will work in Gen4s and the other way around. However, some have had troubles with the Predator board not being able to be screwed down.
Main wire harness is the same as Gen3, but the eye harness is just now one piece. There is no longer a connectiong poin midway through the wire, both the eyes are connected and go sttraight to the board. Should still be interchangeable though. Only aftermarket parts are the Trinity eyes which allow for a greater degree of misalignment.
All Intimidator Solenoids are interchangeable. Gen4s use the same noid as the Gen3s.
Gen4s use the same membrane pad as Gen3s.
Do you really have to ask? Of course.
All Intimidator hoses and barbs are interchangeable.
Gen4s take the same feedneck threads as the later model Gen3s, the milled and not the pressed type.
Gen4s take Gen3 eye covers.
All Intimidator detents are interchangeable.
All but Classic grips are interchangeable.