So many different cartridges and so few shooters.
We have so many choices and so few shooters that there is not that much competition with each cartridge.  How about reducing the choices of cartridges for each Match.   Say, have a “Postal Match” every 2 months (or any time-frame) but for only one class of gun.  Then if we had only had say 10 shooters all would be shooting in the same group.
For instance as follows:
VARMIT SHOOTOUT   using only (204 Ruger, 22 Hornet, 22-250 Rem, 223 Rem, 243 Win).
RIMFIRE SHOOTOUT   using only (17 HM2, 17 HMR, 22 LR, 22 MAG).
HANDGUN CARTRIDGE SHOOTOUT   using only (38 Special, 357 Mag, 44 Special, 44 Mag, 500 S&W, and re-chambers of same, 357 MAX, 360 DW, 445 Supermag and the like).
MID-BORE SHOOTOUT   using only (25-06 Rem, 270 Win, 280 Rem, 7mm-08 Rem).
30 CALIBER SHOOTOUT   using only (308 Win, 30-06, 30-30 Win).
OLD-TIMERS SHOOTOUT   using only (45-70 and 38-55).
SHOTGUN SLUG SHOOTOUT   using only (H&R or NEF guns).
Just a thought to maybe get more shooters and competition.