This is an updating collation of issues/faults other users and I have experienced with the GHK SG55X series (Originally posted in the Heavy Recoil Club discord server).
1, Hop up rubbers splitting. I believe this either only happens with softer buckings or if the barrel/hop up assemblies are not assembled correctly. Addition 10/29/2022 - I have noticed some slight fraying/splitting around the back edge of my PDI 50 degree bucking. However this does not appear to have affected the rifle’s performance.
2, Magazine issues. The clear mags are very fragile. However, the current production opaque mags have been much more reliable. Though a couple of people have had the locking tab fail over time. I personally haven’t had this issue despite abusing mine.
3, Receiver fitment/alignment. This one is a little more undecided. One person mentioned that their bolt lock was breaking after roughly 500 or so rounds and we think this was due to the receivers not aligning properly. Though I’ve only heard this issue cause a malfunction like that once, there have been many reports (including my own) of body pins being too tight or the presence of a small gap between the upper and lower.
4, Upgrade support. Finally, though this rifle performs very well out of the box, if you do find something you don’t like you may not be able to replace it. The only real options you have are replacement hop up chambers, inner barrels, buckings and I think there is a replacement recoil spring. Though there are both comity made and real steal accessory options as well.
Edit: 5, How could I forget the 3rd burst malfunction… A number of people have had their 3rd burst become a 4-5+ round burst. Though I’ve not yet been able to replicate it on my rifle, its generally accepted that this is caused by over lubricating the trigger group.
Edit: 6, In addition to the receiver fitment issue, I’ve herd a couple people report their hand guards (both railed and polymer) being very lose. This should be fixable with either some shimming or by fitting a real steal hand guard.