Between the levels of 40-50 Machinist doesn't get a single skill

[Fannah]

You don't get it, it's a pure DPS gain (no special abilities with overheat for now, so no meaningful dps loss for the 10sec after overheat). There is no need to manage overheat before 62/64.
Then, you can between two fights remove and put your Gauss Barell on, to restart to 0 Heat.

I mean do you get it's very long to reach 100 by spamming all our ammunitions in common fights?
From 0, you need to do 20 GCD to reach 100 without ammunitions.
20GCD = 2.5*20 = 50seconds.
Let say you start with Reload at the start of the fight. 3 GCD without getting heat. +7.5sec. Then Reload at 30sec 7.5sec again, total +15sec. You have for now a total of 50+15 = 65sec.
So you have the possibility to use a 3rd Reload, 3 GCD so 7.5sec again : 72.5sec.
With all this time, you have time to use 4 Quick Reload --> 4 ammunitions, 10 more seconds. Total 82.5sec.
One more Quick reload possible, making it 85sec with Gauss Barell On without overheat.
If you happen to overheat as you will still be in fight after 95sec (the end of overheat), you still made the fight quicker and you still can put your Gauss barell on for the next fight.

You just mean you don't like having to put your Gauss Barell on again, which is ok, you like or dislike what you want, but I just said you don't need to keep Gauss Barell 100% of the time, knowing technically, it's just a dps loss like 95% of the time to get Gauss barell 100% on before 62/64 like you would like to do. Especially knowing we can just drop it and put it again between 2 fights. And for exemple, on my side, I like this style of prepapring myself for the next fight as Machinist, preparing my ammunitions and my barell if needed. I feel like I do something even when not fighting.

PS : It's weird when I just said you don't need it as you tend to believe and people just answer me Machinist "feel incomplete", "unlike Bard", and "I don't want to".
I know and understand the MCH feels incomplete, I agree the Bard is better thought about this, and I understand you would like it to be more manageable to feel like you are using it the way you want.
It doesn't change the fact you don't "need" to (as it would just lead you to a dps loss),. You give me counter arguments which are not counter arguments to what I said.