Gas checks.....?

[dodgyrog]

As above - Adam has said it all.
I, personally, don't use gas checks up to around 1100 to 1200 fps and I leave lube on the groove where the gas check would lie.
Anything above that velocity I would use a check to try and reduce group size.
A boolit without the gas check groove can go faster if lubed well - say to 1600 fps.
Low velocity boolits can be very soft indeed saving precious linotype for the higher velocity projectiles. I really do not see the point of boolits from various sources being so hard in pistol calibres when it can work against accuracy by preventing the boolit from upsetting into the rifling when fired. Similarly, I do not like (or use) lube that is too hard if I can help it although the down side is that the lube migrates all over the boolit when being moved from place to place and I have had complaints of sticky lube all over the boolit which builds up in the seater die. It's a difficult problem and my pistol lube has now been thickened up with Carnauba wax which seems to work well.
As ever in life, it is all a compromise.