On 05,10.2017, China handed over to Philippine 3000 CQ-A5b rifle plus 3 million rounds of ammo. This was the second delivery of this year.
The CQ-A 5.55 is more or less an attempt at a Clone of the M4 Carbines. but there are differences from the US Issue.
First the M4 and all Us versions of the M4 series have the F type gas Block/ front sight base. The lower receiver lacks the M4 extended Feed ramps, the buffer tube extension is the commercial type, and the hand guard only had one heat shield. Current US issue M4A1 features a heavy barrel requiting a H2 buffer, well the Norinco has the lighter older barrel needing only an H buffer.
now how do these affect the weapon?
The F front sight base was introduced to accommodate the M1913 rail system this is as the Flat top upper rail when fitted with carry handle sits a little higher than the A2 carry handle. this means that the front sight and rear sight would not line up. not there are 2 solutions to this issue. Colt and FN M4 and M4A1 carbines added height to the A frame gas block. this new gas block was marked with the letter F to help differentiate it and was later fitted to the M16A4. the Canada and some others solved it by raising the actual front sight post. leaving the rest of the gas block alone.
Early prototypes the M4 was having issues seating ammunition in the chamber. The first was the H buffer. H buffer is a modification of a modification. Early in the M16 history the first incarnation of the AR 15 used a guide rod like what you find in a pistol only bigger, to ensure that during cycling the bolt of the AR 15 during cycling smoothly slid back into the receiver extension. This worked fine with the intended ammunition for the rifle. However when the Army substituted Ball Powder the Ball powder because of it's burn rate changed the pressure profile and timing. This meant that when the Rifle's bolt went back and then moved forward there was still some pressure in the chamber causing the bolt to bounce on contact with the chamber. in automatic fire this would cause the rifle to tap its own automatic sear and reset the trigger prematurely causing a misfire. To correct this Colt created a weighted buffer to replace the guide rod. this buffer had 3 steel weights floating inside it. Now when the bolt moved forward and closed the chamber, before the bolt could bounce the momentum would cause the weights to catch the bounce and ensure the bolt stayed closed.
To correct feeding issues Colt increased the buffer weight by replacing a steel weight with a heavier Tungsten weight. Another solution was devised in the form of extended feed ramps cuts. They extended the barrel extention of the chamber that receives the locking lugs of the bolt. down at an angle allowing the ammunition to smoothly ride into the chamber. Either solution could have fixed the problem M4 however has both belt and suspenders. having both the heavier buffer and feed ramps.
Norinco however only has the buffer.
The buffer used by Norinco is noted as Commercial profile. There are two sizes on the AR series for return spring tubes or buffer tube extension.the Military which and Commercial. Comercial is wider at a diameter of over one and a half inches well military is under. the two are not interchangeable.
The hand guards on the M4 have changed a lot Current US issue have pretty much dropped the round handguards all together for Rail systems. however even if you compare it to older M4s the CQA differs. M4 hand guards were polymer on the outside with a Aluminum heat shield in both the upper and lower handguards were interchangeable. this means that the shooter had less of a worry of burning a hand. The CQA only has one heatshield best placed on the lower side.
The Heavy barrel of the current US A1 came about after experience with US socom where in combat well breaking engagements they had a habit of having one or two shooters open up with long bursts of fire emptying multiple magazines in rapid succession. Now on any rifle this is a torture test, especially if it's done repeatedly. M4 was designed for high commonality with M16A2 and as a personal defence carbine not a squad light machine gun. A1 until the heavy barrel was just the same carbine with a full auto sear as opposed to the 3 shot burst mechanism. Socom and the Army then got into a fight. The TDP of the M4 was locked by the Army. The Army because of there uses had not suffered issues of barrel erosion or burst in the same way Socom was. Socom wanted changes the Army didn't and Colt could only build to the TDP. Finally Socom fed up asked for the SCAR program.
as the Scar program launched finally the Army yielded and Colt was allowed to do a heavy barrel M4A1 The SCAR L then died in the US. The Heavy barrel is by civilian standards a mid weight but required another change. That being the H2 buffer which swapped out another steel weight for Tungsten so 2 Tungsten 1 steel this was due to the effects of the heavy barrel.