Mine has the straight blade scrwedriver type liner with the hole in the bottom of the slot. They need to be coned deep enough on the outside to at least get thru the slot area. My vent is deep in the pan, but there is enough meat there I think to lower the bottom of the pan a little to make it a non-issue. The gun goes off well as it came. If I do ever mess with it, I will lower the pan bottom, cone the outside thru the screwdriver slot area, and cone the inside slightly. The liner is pretty small so there is very little room to cone the inside at all. A bigger problem with it is losing your prime powder as you slip if you are not very careful to hold the gun just right. I have not taken the time to investigate that problem yet. I bought my gun on clearance for 50$ There were two and I bought both. I sold the other for 80$ to a friend. I have 20$ and tax in the gun and it shoots very well indeed for the price!