It has been said many times,
all threads on the M4 copy ARE STANDARD THREADS,
NOT METRIC as the old CQ's.
I have checked these threads on few of the M4 copies
and ALL ARE STANDARD, NOT METRIC:
-barrel/barrel-extension
-barrel nut/upper receiver,
-muzzle/FH,
-buffer tube/lower receiver,
-pistol grip screw/lower receiver,
-mag catch/release button,
-front sight block/front sight post,
-carry handle cross bolts/nuts,
-rear sling loop/screw,
(maybe I forgot some, but who cares?).
The rear sight ramped "thread" on the original M4
is a special thread with a special pitch.
I have compared (by eyeballing)
the military Colt rear sight "thread" with the Chinese M4 copy
and I don't see significant diferences,
but I know that the Chinese one is calibrated
for 14.5" barrels and 62gr. BT bullets,
and it is reasonably accurate to about 300m
The Chinese M4 copy lower accepted
all standard uppers that I put on it.
These pics are of some Norinco parts compared with LMT.
This particular Norinco has about 850 rnds, the LMT is brand new.
For easier ID in all these following pics,
the Norinco parts are
in the upper side or the left side of the pix.
Also, the Norinco bolt carrier is lighter in color, the LMT has a darker color.
Both carriers are chrome lined.
One aspect I don't like on the Chinese carrier is that the outside finnish
is a little rough for my taste,
but this particular gun has a very low serial number
(it is mid 2006 production).
On the newer ones,
the finnish and the overall quality are much better.
This is the Norinco M4 copy with the LMT complete upper on top of it: