Before I started reloading, and then casting, I used to buy Mastercast complete cartridges. Their service was good, their pricing fair, and I never had problems with their ammo.
One thing that did irk me, tho, was headstamps. I ordered .38+p ammo, and it was loaded in both .38 spl and .38 +p cases. I told them about it, and they seemed not concerned. So, you'd get a box of 50 rounds and if they were not in the original, marked, Mastercast box, you'd have no idea if they were .38s or +p's.
If, like me, you have older .38s in which you don't shoot +p ammo, having loads with incorrect headstamps can be a dangerous situation.