Hey guys, not necessarily new to AR's, have 3, one built on my own. But I tried putting a magpul handgaurd mid length onto my Anderson mid length barrel with round handgaurd cap and magpul railed gas block. My problem is with out handgaurd cap rifle cycles fine, but when install the cap it short cycles. Is there a certain gas block to use? I thought that if anything with the cap off the gas block should be slid ahead? A little help would will be appreciated.