E luder thank you for your message
I have decided to sell off my mags, and my gun as a parts gun (just broke my selector switch (did not notice the little nub)
thanks and I will keep this trick in the back of my head for next time.
I am going to guess it was not the rubber and maybe the shim only because one mag is used. The other two are brand new and did not catch right out of the box. So the rubbers should be good unless they are a different size or thickness on the long mags?