As I reload, the finished rounds go into a large tub. I then inspect each reload to make sure the primer is flush, the sides of the hull are not split, the crimp is correct and that crimp end is not "belled out". I discard any reloads with a problem and either shoot these in practice or cut them open and reclaim the components.
A bad crimp in itself is IMO safe to shoot. However, a dished in crimp may mean a light powder drop and a protruding crimp may mean an excess of powder, shot or an improper wad.
Last year, I started finding shells with alternating dished in crimps and protruding crimps. I cut open the offending shells and discovered that the powder drop was erratic and that some shells had very little powder while others had too much powder, which could be dangerous to shoot. I checked out everything on the MEC 9000G and found that a primer had somehow found its way into the powder drop tube. Depending on vibration, sometimes the powder would drop properly and other times the primer would cause some of the powder to remain in the drop tube. this was causing the variation in powder drop.
I removed the primer from the drop tube and everything returned to normal. I then asked myself how a primer could make its way into the drop tube.
Since the primer was unfired, I found out that if the primer feed malfunctioned and I dropped powder into a hull without a primer, I got a jam and a mess on the 9000G. If I then somehow brought down the primer seating ram with a correct primer drop but no hull in the primer station, the primer (Nobel Sport) would be pushed into the drop tube and hang there out of sight.
I now, whenever have an interruption in the loading cycle, I check the end of the primer drop tube with the small end of an Allen Wrench to make sure that there is no obstruction.
Earlier this year, I started getting "belled out" crimps when I switched from 1 1/8 oz. reloads to 1 oz. reloads. Due to error on my part, I was using a 1 1/8 oz. bar with a 1 oz. wad. The larger wad was causing the crimp to "bell out". As the resulting reload was still within safe limits and I had loaded 250 or so shells, I shot these in practice. I had to push them into the chamber of my 870 TC.
I carefully check my reloads and discard any problems to shoot in practice. When I shoot registered, I do not want the distraction of an improper crimp or other problem. All I want to do is load and shoot.
Ed Ward