Painfully trying to get diamond camo

Lately i have been grinding on Call Of Duty WW2. I have been playing non stop trying to get diamond for the Sniper Rifles. The hardest one in my opinion is the karabin. it is so hard trying to get kills with that thing, so i ask you is there a easier way to get diamond camo for the sniper rifles.

WW2 I have 2 guns diamond and I gave up, its too hard in that game to get them there