[rg1]

I've seen it several times in .38 Special and the reason for squib loads in every case was poor bullet tension in thin walled .38 special cases. Some 38/357 carbide dies won't size certain brands of thin walled cases enough to grip bullets tight enough. The primer itself starts the bullet moving before powder has enough time to ignite fully. By the bullet moving the amount of space or volume increases so that you have a very weak pressure. I've seen .38 bullets come from the barrel and fall to the ground 10 yards or so in front of the muzzle and also bullets not make it out of the barrel. IF you can move the seated bullet with thumb pressure or by pushing it against the bench then it doesn't have enough case tension. Only solution if your sizing die won't reduce the necks enough is to get another sizing die that will. Another thing to watch for is if your expander die is doing nothing and you feel no resistance when expanding. A tighter crimp won't help if you have inadequate neck tension.
One method to increase neck tension in thin .38 special cases is to size normally, then switch to a 9MM sizing die (couple thousandths smaller) and run the 9MM die down just past where the bullet would stop when seated. Then expand and load normally.