Yeah, I'm overrun with 20, 30, and 40 round mags but I only have one 10 rounder. Midway USA has some for sale but I was hoping to find some gently used (aka cheaper). I've found that exiting a vehicle in a hurry, the 20 round mags can snag. I guess I'l give the 10 round plastic mags from Midway a shot and see if the function.
You might check with C Products for the dimensions on their 10 and 5 rounds mags for the AR. C Products Store
I have one of their 10 round mags that came with my RRA AR and it is smaller but I'm not sure if they'e still making them. It works fine.