Air Gun Tips from around the Globe: "To rectify transfer port problems I prefer to use a small ballend steel burr in a Dremel tool at very low speed. The smallest rechargeable Dremel on the market is an indispensable tool when working on guns for me. If I can access the transfer port with the ballend burr I use it to'break' the edge of the transfer port by grinding the sharp edge to a less aggressive profile that won't catch the pellet, but allow it to slide past without damage. It isn't possible to get a ballend burr into the port area on many guns so your only recourse in that case is to create a slotted rod or dowel that you can wrap with fine emory cloth or sandpaper. This should also be a follow-up step to the port clean-up with the Dremel. The bolt will have to be removed to use this method, but it's not too difficult with most guns. "