Some .410 shotguns can chamber a .45 colt. This is a completely true statement. Some .410 shotguns have even been specifically designed to be able to fire .45 lc cartridges. The problem is that not all of them are, and that just because it fits, it doesn't mean it's safe. Some .410's can chamber .454 Casull. Actually firing it would be a very bad idea.
If your son takes an H&R Pardner that was only intended for .410 shotshells, and fires a .45 cal bullet down a .41 cal barrel into the full choke it probably has, he will have a very bad day.
Read the stamp on the barrel. If it doesn't say anything about .45 anything, don't do it.