With the most recent update, the co-op points counter has been messed up, allowing you to unlock weapons with only a fraction of the required points. Here's how it works:
Let's say you have 10,000 points in actuality. The update added a 1 to the end, making your recognized points 100,001! Here's how my log looks:

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Before updating, I had 6,066 points, and my stats show for it.
I'm not sure if any matches played after updating will continue this trend, but here's to hoping you had a good amount of points before updating!

-Tupac