What is there to be learned here? That your garage listed Rate of Fire (rof) is incorrect.
The only time when it is correct would be when your crew is 91% trained on that tank with NO Improved Ventillation, Shell Rammer, Brothers in Arms (BIA) or 10% premium consumable (Cola, chocolate, pudding and tea, etc)
Once you reach 100% crew your stats are actually better than listed... Read on and I'll explain why.
So I've been doing some investigative math with reload times in-game and there's a few things to point out before I begin
•"Characteristics for a vehicle with basic configuration and a crew with 100% qualification."-quoted from the WoT Xbox Tankopedia
•When a crew is not at 100%, "Master your tank to activate your Skills & Perks" will appear superimposed over your perk and skill display in the garage. This is said to be a visual glitch as your perks are still active. What it's been assumed to mean is that you must reach 100% tank proficiency before you may continue to research perks and skills. Going off this basis, the math behind in-game reload times supports that BIA still adds 5 whole points to each crew member's effective skill.
•The commander provides a 10% boost to all crew members besides himself. So when a crew is listed as 100%, the rest of the crew are effectively 110%
•Degressive stat equation (a stat that decreases when improving- reload times) nominal stat * 0.875 / (0.00375 * effective skill level + 0.5) - equipment bonus %
•Progressive stat equation (a stat that increases when improving- round per minute) nominal stat / 0.875 * (0.00375 * effective skill level + 0.5) + equipment bonus %
That being said, I was under the assumption that the garage stats for rounds fired per minute took into account the 110% factor but it doesn't and here's why...
T34 premium heavy: 4 rounds per minute= 15 second reload. Well after timing my reloads with 100% crew and nothing else equipped my observed average out of 12 reloads was 14.39 seconds (4.169 rpm). Now if you calculate the equation based on 110% effective skill level the math proves that the garage stat is based on a loader with only 100% effective skill level.
15 * 0.875 / (0.00375 * 110 + 0.5)= 14.383 second reload vs my observed time (OT) of 14.39
4 / 0.875 * (0.00375 * 110 + 0.5)= 4.171 rounds per minute vs my 4.169
T26E4 Super Pershing:7.32 rounds per minute=8.196 second reload. Equipped with rammer, vents, BIA & Cola my timed average reload time from 12 shots was 6.51 seconds (9.216 rpm)
8.196 * 0.875 / (0.00375 * 132 + 0.5) - 10%= 6.486 second reload vs my OT of 6.51
So you've just gotten that new tier X T110E5 but don't want to move your crew from the M103 because your friends are grinding IXs still... Let's see what the differences are between the different crew levels and equipment.
T110E5: 6 rounds per minute= 10 second reload
50% crew> 55% effective crew= 12.38 second reload
80% crew> 88% effective crew= 10.54 second reload
80% BIA, Vent> 99% eff. crew= 10.04 reload. With rammer= 9.03 reload
100% crew> 110% eff crew= 9.58 reload. Rammer= 8.63
100% BIA, vents, Cola> 132%= 8.79 reload. Rammer= 7.91
So looking at an 80% crew with a 5.69 rof vs. a 100% crew's 6.26, we see a 10.01% difference. And from the garage stat of 6 rounds per minute vs. 100% crew's 6.26 there's a 4.4% in game difference.
*colored numbers are garage stats while numbers highlighted of the same color are the actual numbers seen in-game.
Note: if your crew is in a tank type that's different than the one it was original recruited to there is a 25% crew skill penalty to be factored in as follows. (crew skill level + vents + BIA + premium consumable) * commander bonus * 25% penalty= Crew skill (100 + 5 + 5 + 10) * 1.1 * 0.75 = 99 effective crew skill level. WG is acknowledging this penalty and a fix is is the works.
^^^patched as of Update 1.3^^^
If quoting some of this writeup, it would be appreciated if you were to delete it down to what you wish to reference or question to save the clutter. Thank you for your reading attention.