Power of the machine gun?

[=SE=Sova]

Hello guys.
This is the list of the mods i am usinig:
FX_Update_0_0_19_ByTheDarkWraith
NewUIs_TDC_7_1_0_ByTheDarkWraith
Manos Scopes-patch for 16x9
IRAI_0_0_37_ByTheDarkWraith
gap - HD 1 deg Scope Bearing v 1.0
EQuaTool 01.01 by AvM - Kriegsmarine Woody Golden Style
Accurate German Flags
Church's Compass Dials Mod v2.2 - Option Two
Trevally Harbour & Kiel Canal Pilot v2.9
Trevally Automated Scripts v0.6
OPEN HORIZONS II Light v3

I can say exellent work.I like it alot.Water color is great.
I did notice one problem in the game.
I was at periscope depth, 1500 meters from the convoy.Enemy has spoted my periscipe and start to fire with machine gun.I had periscope damage,diesel engine damaged,one oficer hurt,flading,hull damage....

From my military knowlage,macine gun big caliber cant do this.At that distance to penetrate submarine,at that depth.It is OK for deck gun,but not for the machine gun.
Eny opinion?