Yes it’s somewhat common. That is why you check for interference fit before glue to verify good mating contact. Like Jack said pipe can have slight difference od. Fittings are usually very consistent.
IFC 3rd party certified in Residential & Domestic Fire sprinkler systems, Wet & Dry Risers and Commercial Fire Sprinkler systems Specialising in High rise,mixed use occupancies,PBSAs,BTRs & Houseing developments
Has anyone came across this before? The pipe wall thickness was thinner than normal causing 2 x fittings to blow off at 5 bar pressure. Having the fittings blow off not once but twice alerted our engineer to stip the Length out and start again and that's when he noticed the difference in thickness. This part of the install was carried out by one of our new apprentices that never realised the problem. zero damage and the system is back up. I personally have never seen or heard of this before.