Best way to get a lot of 41-50 crystals?

Finally decided to check the endgame ammo and noticed they have some really strong effects like 25% more damage based on certain keywords on top of ammo damage.

That makes it quite valuable and it makes sense its expensive to craft, most of the stuff are easy to farm but in my case, the ammo i want uses lvl 41-50 crystal drops which drop from endgame silos and high level areas.

What methods exist that make farming those max lvl crystals faster? Other than simply doing silos