Is it possible to bake the bullets too long? Or too hot?
I just recently experienced my first powder coats that failed the hammer test. For years they all passed the hammer test so the only "failures" were from poor coverage not failure to cure.
The first time I had a failure to cure I didn't get good coverage with the first coat so I gave them a second coat. On the second coat I failed to start my timer so they baked well passed the 25 minutes I usually set them for. When I pulled them from the oven they looked well coated but had not-so-glossy coating and some of the bullets that were directly over the heating elements had very slight slumpage (almost looked like it could have been fixed by sizing). Before sizing I gave one the hammer test and to my horror the paint flaked off the out edge as the bullet flattened. I found a reject bullet from this batch that had been given the first coat with the others but I rejected it before putting a second coat on it. That bullet passed the hammer test.
Now just yesterday I made a batch of roundballs and coated them (one, good coat). This time I stopped the oven shortly after the 25 minute timer. After they cooled I hammer tested one and it failed. Granted since these will all be surrounded by a cotton patch when loaded in a muzzleloader I don't need to re-melt these, but still - I wonder what's up.
I've tested the oven with an oven thermometer and it's accurate. The 400° setting produces a 400° reading on the thermometer just as it has for years.
I read this forum for quite some time and I've never read anyone having problems with baking too long. Too hot produces melted bullets, but I have not read of bad consequences from baking too long. Is it possible? If so where's the margin? If 20-30 minutes in a pre-heated oven seems to be the standard recommendation, has anyone gone past that for say 45 minutes? an hour? an hour and a half? What happens?