I had a Range Master show me a picture of a Glock that had blown up. The owner shot cast bullets, then a jacketed bullet. BOOM! I was told this was a regular occurrence at this range. To each his own but when the Manufacturer says you should not do it, is it really a good idea??
I always like these stories for so many reasons.
I have seen a few that have been blown over the years. In every case here is the story of 4 guys I have met over the years.
1. Is the bullet lead or zinc?
2. How hard were the bullets?
3. Did you know there was parts of your bullets in the bore?
4. How thick was this build up?
5. What kind of speed are you getting out of your new 40?
Their answers follow
1. Just a blank stair then an answer of lead.
Wheel weights are now zinc not lead and have been so for a very long time. Tell them this they will tell you they did not know that but they got the lead from a local shop and their bullets are lead. When in reality they are zinc.
2. They never know.
3. Only one of the 4 guys knew there was "leading" or in reality "zincing" of the bore. But the day it blew he did not look to know for sure.
4. How would they know they never looked.
5. All of them shoot loads that are questionable at best. It seems like most of the 40 shooters out there like to replicate 10mm speeds.
Granted this is only 4 handguns but the story was replicated by 4 separate guys who as far as I know never met eachother. When I tell this story most are shocked that they are all 40S&W. I am sure others have the same stories about 9mm and 45acp handguns but I have not met them yet.
Now to answer your question of "is it really a good idea?". That is a tough question to answer. If you are a person who just shoots and does not think. Well then it is not good. If you are a shooter who is thinking and looks at their equipment and are willing to accept what happens. Then sure it is a good idea. This is how we learn. It is like the first guy who tried powdered paint to coat bullets. Nothing ventured, nothing gained.