Parker 45 Flighter, nib fitting problem

[ItsmeMario]

Hello, I'm new to this community and I just introduced myself in the appropriate section.

I'm new to the fountain pens world, and in December 2018 i acquired a nice Parker 45 Flighter. Before telling you which problem I'm encountering, I would like to introduce you my cheap but good looking Parker.

The pen is a Made in England Parker 45 Flighter, the date code is "QL", so it was produced in 1980, and I received it in this Parker box:

Outer cardboard box


Inner plastic box:


If we open it, this is what we find inside, the pen is held in place by a plastic pen holder:


Lifting it, we gain access to the user's manual:



And here is the pen, I already drained 4 Parker cartridges, the seller gave me two of them with the pen. It was like new, and still looks like new:



Fitted with a medium stainless steel nib, the collar around the feeder says "M" too:



And here is the Parker converter that the seller sent me the pen with:


And now, we get to my problem, recently I acquired a Parker 14k nib, this one:


Judging the size of it, and comparing it with my medium stainless steel nib, I'd say this one is an extrafine nib.
So what is my problem?
Whenever I try to fit the 14K nib into the feeder, with my M collar, the fitting is a bit stiff and I have to push the collar down more than I'm used to with my M SS nib. I disassembled the pen already, and cleaned it all, but this is how the 14K nib fits:




I'm afraid that the nib point is too wide open.
Did someone had this problem? And how do I solve it?

Thanks everyone

Bonus:
I realized this genuine leather pouch for my pen myself, tell me if you like it:



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