I like this mod but...
Can you up the damage as it doesn't use the standard ammo, maybe make it a turret 2.0 and add some new ammo types.
I like the idea of fragmentation rounds that would shred the mass of Small spitter and Small biter.

Don't forget that the main purpose of this mod is a capable AA gun. The non-AA use case is second in priority.
And since I wanna stick to realism when it comes to ammo types for this gun, I won't be adding new ammos, sorry.
The current ammo is already stronger than uranium and the shooting speed and range is also superior to the normal turret.
However I obv won't stop anyone from making additional ammos as new mods ^^ It's just not my vision for the normal version of this turret.

Then i may have a bug become it does less damage then the uranium ammo and the speed is slower vs the normal turret

That does sound weird, yes. You could quickly test the mod without any other mods active (I'm assuming you use others) and see which other mod changes those values. Or give me the list of your active mods. Or provide me a save file with your active mods and mod settings.

It's the damage buffs that are different and and only applied to the ammo.
Like when you do a damage buff research it ads 20% with each level to both the ammo and the turret but yours is only to the ammo.
I can't remember the exact percentages but yours is 15+21 damage and the uranium is 24+48 damage.
I have the level 11 damage buff giving turrets a +200% and your a +140% buff.
The first buff for your starts at level 5 so that would explain why it's 60% less, i can't remember when i added your mod, could it be that i was already in a game game when i added it and that level 5 was the next buff after so that's when it started adding the buffs from that point?

The turret shooting speed bonus is independent from the damage bonus. Its 3 rounds per second faster than the vanilla turret.
And I have to correct myself, its slightly weaker than the uranium ammo. You have to add both dmg types though. Flak dmg is applied on entities flat with no resistances xd Only my planes have some resistances.

And you did nothing wrong with the adding the mod later. Factorio applies the bonuses regardles of when you research a tech or add a mod.