Ww1 77mm shell introduction

[ArtilleryManiac1916]

Hello guys , i ve got a question when this shell was trurly introduced. Since deminest number 7 tells that it was put into service in 1916 to replace k.gr15 grkz .
French site guerre des gaz supposes that first usage was in april 1917.

I understand that the exact date when it came out of the factories for the first time and then sent to the front maybe unknown , but please can someone tell ? Wich is closer to the reality.

 

[ArtilleryManiac1916]

So the long shell was mentioned in my documents starting from july 1st 1916 (British report to the eastern command)
Hence.. Sir Belot was right.
The long chemical shell for field kanone 96/na was indeed introduced in the middle of 1916 ,but had just greencross or fosgene.
The grkz 1 most likely appeared 1917 as the french website states.