My next reloading project is loading .303 Brit for a No.4 Mk1 1943 Enfield. I am planning on neck sizing with a Lee collet die once fired PPU brass fired in the rifle. I have some Speer 150 gn .311 and some Hornady 174 gn .312 bullets on their way to me. I plan to start with these. But, I have a bunch of Hornady 124 gn .310 vmax bullets that I use in 7.62x39 that I would like to try as well. I have read a number of posts that say they got reasonable to good accuracy with them. My question relates to neck sizing with the .303 Brit collet die and neck tension using the .310 bullet. I am anticipating that the neck tension may not be enough with the slightly smaller bullet. Would appreciate any advice from anyone who has been down this road.