How heavy is China nuclear warhead? China doesn't have nuclear-armed cruise missile like BGM-109 Tomahawk or AGM-86 ALCM meaning that China nuclear warhead have more fissile material and actually very heavy (need more rocket fuel to carry). China needs more nuclear test to miniature their nuclear warhead(physics package). Maybe can test in north korea to avoid worldwide sanction. For example W80 yield 150kt and weight about 130kg compared to china lightest warhead yield 200kt-300kt which is 500kg.Some suggest China has long had no less than 1000 warheads. The 300 warheads China has is an estimate from many decades ago. Even when there was little threat to China from both the Soviet Union or NATO. In fact those estimates for around 300 warheads came in an era where China was close to NATO and more aligned with western powers again the Soviet Union. There has never been much sense after the 1970s and before 2000s to hype up warhead count.
Therefore 300 estimate is already more likely to be lower count than real number even back in the 1980s and 1990s where this estimate is from/ worked from.
Now there is every reason to pretend to have a higher warhead count in order to improve deterrence but there is even greater reason to actually have a high stockpile.
So think about all that and the fact that no one truly knows how many China had in the past and have in the present. Then consider that enrichment and warhead design are easy problems now for China who holds both the two known warhead configurations (one of them exclusive to China). China doesn't report weapons grade material reserves and the best estimates can only work with how much fissile material China imports and how many different types of known reactors China has. These produce extremely variable estimates on how many warheads China likely has. Then there's the fact that China has reserves of fissile material within its own land.
Then there's the problem of yield. Larger yield require more material but how much more we do not know here. It could have 3000 warheads of lower yield or 1000 of higher yield for example. When it comes to warheads, there is simply no way for the non-initiated to really know. The 300 estimate is likely way too low because it is an extremely dated estimate from an era where China would have only been under-reporting how many they own and from an era where China has little to no threat while attracting massive amounts of international investment. Nowadays China has every reason to stockpile due to mounting western threats and even more means to build a larger stockpile.
W80 warhead ~150kt max yield. Look at how small it is. I can't believe this thing is 7 times more powerful than Fat Man