Extra mods done on Bob’s impact;
1: front of valve housing was milled larger
2: 6.50 VS
3. Rod spring moved 3” away from rod delrin seals
4: rear block gauge connect through hole was milled larger for the external plenum tube for faster flow to feed the valve.
5: double transfer port on barrel and pellet probe.
Source
Can you give an explanation of mod#3 ?