As already pointed out, polygonal barrels have been around A LOT LONGER than FMJ/HP bullets have. Do you think they were shooting paintballs or something?
Jacketed bullets came about due to increasing chamber pressures and velocities. The reason there were no issues shooting lead bullets through polygonal rifling before jacketed rounds came along was because the pressures and velocities were very low.
... someone on a forum said so.
That is a remarkably inaccurate summation of the evidence that has been presented on this thread regarding the issues with shooting unjacketed rounds in polygonal rifling.
But for those that know how to take care of a pistol, and you've done your homework, then you know that you can safely shoot hard cast and lead bullets in your CZ-82.
I should point out that the reason the forensic engineer became interested in the topic was because, in spite of knowing how to take care of a pistol and in spite of doing his homework, and after firing many thousands of rounds without incident, he blew up a pistol with polygonal rifling by shooting lead bullets through it.
His subsequent testing proved the cause of the incident conclusively.
You're certainly welcome to your opinion, but to suggest that your opinion, based on your limited experience with polygonal rifling should supercede pressure and velocity measurements made by a forensic engineer is somewhat reckless.
It is possible to get away with using lead bullets in polygonal rifling but without very carefully monitoring pressures (or at least velocities) it is not possible to make an accurate statement as to whether or not it's safe to shoot unjacketed rounds in a particular gun.
Even proving that it is safe in one particular instance of a model of firearm does not imply that it is safe in other apparently identical instances of the same model of firearm due to the fact that even very minor expected differences in chamber/bore from one firearm to another can make signficant differences in how that particular barrel lead fouls and in how many rounds it will take to generate an unsafe condition. The late Gale MacMillan, who knew a thing or two about barrels, once made the following statement to those who insisted on shooting lead bullets through polygonal rifling: "If you haven't had trouble just be patient."
Furthermore, the implied claim that you have done your homework on the topic is called into question by the fact that you contradict Allan Jones, Beretta and others who state categorically that the practice of trying to remove lead fouling by firing a jacketed round down the bore is highly inadvisable.
To be perfectly clear, if you're currently getting away with shooting lead in a polygonal barrel then I'm not saying you're cheating death. If you continue to do exactly what you're doing now then the odds are you'll continue to get away with it. But if you go buy another gun you should not assume that what's keeping the current gun from leading will work for the second one. Same for the similar gun your friend owns. And if you change something in your load or fire a few more rounds than usual in a range session there's no guarantee that you'll still stay below the safe limit. You're probably safe doing EXACTLY as you have always done with the loads and guns you're using, but even that isn't a guarantee of continued safety.
The forensics engineer blew up his gun at around the 23K round mark. Part of his investigation and testing was done to try to determine how to remain safe while using lead bullets in polygonal rifling. His testing drove him to the conclusion that there is no good way for insuring safety short of careful pressure/velocity measurements. He now uses jacketed or good quality plated bullets in his reloads for polygonally rifled guns.
