Worst handloading goof I've yet made was sticking a bullet in the bore of my most prized revolver. At least I was good enough to not
fire any after it.
The after-investigation painted this picture:
--I was using a powder that meters really poorly, and I likely got just a bit less than I thought
I was getting in that round
--I was using far, far
too light a powder charge for the round, the bullet, and the gun from which I was launching them
--I was going really baby with a PLATED bullet, which I have constantly (since that day) attempted to warn others not to go so lightly & reserved
--I was shooting these from a revolver which has the added affect (however small) of releasing some of the pressure from behind the bullet in the jump from cylinder to forcing cone...which will not EVER help you when you've got ammo that's well underpowered.
With that said, I think it makes very good sense to tell us the bullet construction and weight, and the powder type and charge weight of these loads that gave you erratic results. Just because of my own experience, my first reaction is that -ALL- the loads you made & brought in .38 Special that day were powder puff loads...too light overall, and two of them happened to be ever-so-slightly lighter, and when they make that jump across the flash gap, some of the much needed gas is escaping and not helping the situation.
That may not be the situation at all - - but that is what occurs to me without more information about the load.
I'll also take a moment to highlight something already said:
This is why I like batch loading using a loading block, charge 50 cases at a time, check the charge using a light, seat the bullets
I've got like 40,000 loaded rounds over the last two years and God's honest truth is that I've looked in every single one of them by peering over a load block, usually with 50 rounds in it, and seen all
of my happy powder charges before I place a bullet over each one.
I have complete and absolute faith in my handloads, and THAT step is the biggest reason why. It is very nearly the definition of "warm & fuzzy."