I highly doubt that since China makes its own varient of Russian weapons, and aircraft. Russia never supplies China with actual aircraft, even today. China is just given the blueprints basicly, and they make the Russian varient sutable for their pilots, and make some modifications. If you look at a Chinese MiG and a Russian MiG, they will be very different in some aspects like engines, control positioning and wiring from time to time (This can be said for the Chinese MiG-21).
Same with weapons, the Chinese Ak is smaller than the Russian Ak, and in some instances are completely different on the inside, but look the same on the outside.
Chinese made or designed Soviet/Russian military equipment are: 1) Kit assembled or Soviet/Russian made. 2) License built in larger degree by China. Essentially licensed copy. 3) Unlicensed copies. 4) Localized variants based on license or unlicensed copy.
Modern Chinese tanks are good example, they are evolved from fifties Soviet tanks not from newer Russian designs. Technically pretty close to same level in sophistication as what Russians make in many ways. Another good example is Chinese J11, it's local variant of Su-27. First production batches were basically Russian made planes that were assembled in China, those had some Chinese parts. Later production batches have included more Chinese made parts and sub systems. Many of ingenious Chinese designs use Russian parts and sub systems, J10 fighter is good example of this. Current models use Russian AL-31 engine as it's lot better performer than current ingenious Chinese engines. Chinese WS-10 engine has theoretically better performance (higher thrust, better fuel consumption), but it's FADEC (basically computer that controls engine and it's accessories like fuel pumps) isn't fully mature design yet so it doesn't reach that performance in suitable time witch makes AL-31 lot better in reality.
Basically all older Chinese Soviet designed military equipment is from era before Chinese-Soviet relations went down. Soviet transferred most of documentation and toolings for MiG-21F before that, it took China fifteen years to actually start producing copy of it. Cultural revolution slowed it lot. Still Chinese didn't have expertise in designing relatively modern fighters so J-7 was hopelessly obsolete when it entered service in late 70's, it was inferior to newer versions of MiG-21 like bis or PM. China later had access to newer Soviet gear thru third parties like Egypt and Iraq.
Difference in Chinese AK's and Russian AK's isn't really size but measurements of certain parts. Stock length isn't that important issue technically, it's important to ergonomics but that is entirely different thing. Measurements of some internal parts are different, those are different mostly due to non functional reasons like production costs. Some parts of Chinese AK's and Russian AK's are still compatible. Most important difference between Russian AK and Chinese AK is quality control and materials, Russians have bad quality control and but use relatively good materials in production and Chinese have downright horrible quality control and use low grade materials. Difference in accuracy when compared to western assault rifles is mostly production tolerances, not due to design even when it is minor contributor in certain features like balance shifts due to heavy slide or not direct recoil transfer, those mostly affect in rapid single shots. Finnish 7.62rk62 and 7.62rk95 are AK's made with high production standards, those are amongst most accurate assault rifles there are in world.
Like you said weapons may look similar but may be entirely different inside, better example than Chinese and Russian AK could be difference between AK and Vz-58. Weapons with exactly same design but not compatible parts is another thing, difference between metric and imperial measured FN-FALs is good example. British L1A1 is made with inch based measures where most of other FN-FAL's are made on metric (original, Austrian StG-58), differences are tiny and basically impossible to see without comparing.
Actually the QBZ-95 and QBZ-95B is a varient of the British Bullpup Assault Rifle, licensed by China. It is not a Chinese varient of the French FAMAS.
Wrong. It's Chinese design, not license made. Bullpup is basically just lay out of design, one that places trigger in front of action. It's not even British invention as far as I know. UK just came up with typical modern form in rifles as first with EM2 prototype assault rifles in late 40's and early 50's. First bullpup rifle that saw somewhat widespread use was German paratroopers rifle FG-42, that one wasn't assault rifle as fired full powered rifle round (7.92x57 Mauser) but closer to light machine gun in it's tactical role. It's magazine was on side of stock behind trigger and pistol grip.
In our world, they had lots of ideological differences and territorial issues that strained their relationship quite heavily.
In 1966 they even ceased all diplomatic relations with each and did not restore them before 1987 !
At one time China even accused the Soviet Union of "social imperialism"
In 1969, the situation deteriorated so much that both came to the brink of war. A few shots were fired over a dispute about the Zhenbao (or Damanskiy) Island.
You see, i would not take it for granted that they must have been allied in the Fallout world.
Besides own small border dispute Soviets and China had different allies. Pretty much only communist country that had good relations with both was North Korea. Vietnam witch was supported and supplied in war against USA by both choose Soviets as an ally. China supported Cambodias Kmehr Rouge, probably most murderous regime that has ever ever existed*, that was taken down due to too bad human rights violations by Vietnam witch intervened to Cambodian civil war in 1979. That led to border war between China and Vietnam. China attacked when most of Vietnamese army was involved in Cambodia, got stopped probably largely due to Soviet pressure. Both sides claimed victory, border remained same and Chinese casualties were higher.
*Pol Pot and buddies killed probably between 1/4 to 1/3 of population that lived under their rule depending on estimate. Hitler, Stalin and Mao seem to be n00bs when compared to proportional body count/death toll.
In Fallouts alternate timeline Soviet neutrality would seem to make sense in plenty of ways. First is diplomatic relations with US during war. Another small hint could be AK-112 assault rifle, that is in FO and FO2. Even that bit strange assuming few things common with Soviet small arms designations that in usually go by format type of design, initial of (chief) designers surname or by combination of designers if there is multiple designers and if there is numbers it's in most cases year of that weapons acceptance to service. AK implies Automatic (rifle) Kalashnikov and 112 could be 2012. There is plenty of those in USA and it uses same caliber rounds as definitely US weapons. But I have to say that designers of Fallout didn't seem to be having clue about weapons design (technical) and history at least based on descriptions of weapons and images used. Stuff like G11 being modern, in real life designed in 1970's and 80's, so it's just about hundred year old design at start of war. Another small things like sniper rifles caliber, 7.62x51NATO (aka .308Win) isn't FO but in FO2 it's there. Another thing that makes me wonder a bit how many 5.56NATO (.223Rem) guns are more powerful than 7.62NATO ones. Bozar being 5.56 machinegun and using picture of Barrett M82 that is 12.7BGM sniper rifle. You know, details.