The gun ports on the F-22 and F-35A are visible, and we have seen them in action, as well as launching and carrying AAM, as well we have seen the J-20 carrying AAM, but we have not seen the J-20 with an open gun port. If they have shown us the internal weapons bay open with AAM on pylons, isn't it logical to assume we would have observed the cannon as well if it was indeed mounted.
I have to stop you here, because I believe your premises and logic is incorrect in two ways.
1: F-22's gunport.
F-22's gunport is actually very difficult to spot -- we only think it is "easy" because we all already know where it is. If you give a picture of F-22 to anyone who's never seen the F-22's gunport before, they would almost definitely be unable to positively ID where it actually is, let alone prove it. F-35A's and PAK FA have slightly more visible gunports, for their own reasons (design choice, internal volume space etc), but F-22's gunport is almost impossible to distinguish if one didn't know where it already was.
2: you say that we have "not seen" J-20's gun port.
However, the opening of a gunport for stealth fighters typically only occur during testing of the gun itself. In other words, we will probalby only ever see the J-20's gunport (if it exists) if we receive footage of the gun port being tested. In other words, it is completely reasonable for us to have not seen J-20's gunport being open.
(Seeing J-20's weapons bay open on one occasion does not mean it is reasonable to expect to see J-20's gunport open. You make it sound like they are interested in showing us what weapons bays or doors the aircraft actually has... when in reality a gunport on a stealth aircraft typically only opens when it is being fired)
As I mentioned in a previous post (
https://www.sinodefenceforum.com/j-20-5th-gen-fighter-thread-v.t7303/page-280#post-418026), the main arguments for why J-20 may not have a gun port is basically "we haven't seen it", and I think this is a terrible argument.
Remember that J-20 is a stealth fighter with large internal volume (meaning a gun port likely will not be very visible, ala F-22) therefore we will only be able to positively ID a gunport once it is opened.
Next we should consider that gunports for other stealth fighters are only seen open, by us civilians, when they release test footage of the gun being fired. Then, remember J-20 is being developed for the Chinese Air Force, and so it makes complete sense that they haven't released test footage of the gun being fired (if it exists), because they care about OPSEC.
Don't forget that the F-35B and F-35C are NOT equipped with an internal gun, even though they are both tasked with "fleet air defense"??? So if the J-20 had a gun, its likely that we would have at least seen the barrels exposed, even if they choose not to show weapons testing, just as we have seen the AAM on the internal racks of the weapons bay.
Negative -- if J-20 had a gun, it is likely we would not see it, because the gunports of stealth fighters typically only open during test firings. How many occasions have we seen the gunports of F-22, F-35A, or PAK FA actually "open" on occasions which did not involve test firings?
I can not think of a single one.
That, along with the fact that J-20 is a stealth figher, and voluminous at that, means it has a lot of space to put an internal gun without having it bulge out like F35A or even PAK FA, meaning it can be virtually impossible to distinguish from the rest of the aircraft, if it is there.
I'm not attempting to prove the J-20 has no internal gun, I'm simply observing that we have NOT seen it, or clear evidence of its existence??? I'm not emotionally invested one way or the other??? but others obviously are???
I'm emotionally invested only in the way that people have reached their conclusion in arguing that J-20 supposedly doesn't have a gunport, because I think their logic makes no sense. I think they are relying only on their eyes and not thinking about whether their eyes are useful in this case.
I'm not particularly invested in whether J-20 actually has a gone or not -- I personally think at this stage there is no clear evidence for or against the gunport being there, because we haven't seen any positive ID.
However, at the same time I think people who are saying "we cannot see a gunport therefore there probably isn't a gun" need to re-examine how they reached that conclusion and look at the premises for it, because J-20 is a stealth fighter with large internal volume so it should be
expected that an obvious gunport would be almost impossible to see.
So at best, right now the situation for the gun should be: "there are no positive IDs or confirmation of a gunport, however this does not suggest a gunport does not exist on the aircraft, because it is very reasonable to expect a gunport to be very difficult to identify on an aircraft of this type."
Or, putting it in a single sentence: a person can say we haven't seen J-20's internal gun, great, but that says nothing about whether it actually exists or not.