I don't have a Vaquero, just Blackhawks, but I'm wondering what caliber, what loads? Are you not hitting point of aim or just all over the place? Do you shoot OK with other single action revolvers? Lots of Questions, I know.
Verrry often ppl point the finger at the gun first and never consider the person behind the trigger. It's not a simple ammo, A, gun B and shooter C and have it equate to magic. Gotta find consistency for the shooter first, the technique used is paramount in importance. Proper grip, hold, trigger control...
Then try various ammo to see what shoots best in your gun.
I have two in .44 Mag with 5 1/2" barrels for CAS. I find both of them to be very accurate with my .44 Special handload using Unique powder and 240 gr. semi-wadcutter lead bullets. You may have to experiment to discover what it likes, just like most other guns.