Originally Posted by
longbow
I find it hard to believe the added weight of glue would be enough to cause over pressure, it can't be more than a few grains... but I'll check.
What I can imagine is if the slugs are soft and they obturate in the hull/chamber then hit the forcing cone that they might not squeeze back down as easily as an unfilled slug. I have related my bad experience with a blown up shotgun several times and that is one of the causes I blame... filled slug obturating in the chamber (which I know it did) then not being able to squeeze down fast enough.
Not questioning your comment about being over pressure but the cause of being over pressure.
Longbow