Is this Mini 14 Magazine Broken?

[dubious]

I've got a new mini 14 with the standard 5 rd mag with a plastic fancy baseplate, which locks in easily. I also bought a 10rd factory mag which has an older style metal baseplate and wont lock in for the life of me. I think perhaps it's faulty? Here's a pic of the back of the magazine. Is it missing a tab?

 

[rcmodel]

Yes, it is missing the tab.

rc

 

[dubious]

Dangit, I'm not getting a lot of factory ruger love today! :banghead:

Thanks rcmodel, you're a peach!