Any pointers on breaking in my new M4? I Plan on running 00 Buck & 1oz Slugs. 2-3/4" only no 3". Do I need to remove the factory choke before firing slugs? I changed out the magazine tube, spring and follower from Freedom Fighter Tactical parts. In order to be compliant with ATF 18 U.S.C $ 922(r) i need to replace 2 or 3 more USA made parts i.e. Forearm, Trigger and or Trigger guard, etc. what are anyone's thoughts on being compliant with 922(r) and breaking in a new firearm???