(adsbygoogle = window.adsbygoogle || []).push({}); Me personally the hardest one was Model 1887 then pkp pecheneg.
The model took me half of my 5th prestige and the pkp pecheneg took me around 8 hours of 2x weapon exp.

The easiest gun for me was pp90m1. I got it gold the 2nd day of release only running rapid fire and extended mags. after that it was the l86 lsw. All I ran was grip until I got to level 30 then I did the rest of the attachments.

the model because its COMPLETE shit without range :p

Model is pretty is the only one that is challenging. Rest are either very easy, or just not that hard.

Easiest: MP7, PP90, P90
Hardest: Model 1887

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FAD that gun suck