HKP Brand MP-5 40/10 mags don't work!

HKP Brand MP-5 40/10 mags don't work! These are the clone plastic magazines put out by HK Parts, Inc. I ran into a serious issue trying to cock my factory originanal, all stock, MP-5/40 SMG, the HKP clone mags interfere withj the bolt carrier and won't allow the gun to be cocked.