NO...It is NOT normal.A friend has a Diamondback 38 Special which chambers 357 Magnum ammunition.
Is this normal?
It's also very dangerous for the shooter and anyone unfortunate enough to be standing nearby.
The Colt small "D" frame revolves were never made or heat treated to accept .357 Magnum level pressures.
Some fools have been known to re-chamber older .38 Special small frame revolvers to accept the .357, but they are literally a hand grenade.
Some modern small frame revolvers were strong enough to allow re-chambering, like the Ruger SP-101, and some small frame S&W and New Colt King Cobra's are made for the .357.
Older revolvers like the Diamondback are simply not strong enough.
The problem is, they can be fired with the Magnum ammo, but sooner or later it's going to fail and someone gets hurt.
The key words are "sooner or later" which means that people shoot them thinking that since it hasn't failed yet, it won't.
It's common to advise owners of these re-chambered guns that it's not safe, but since they've usually been shooting it without it blowing, they tend to ignore you.
If you're a good person you might tell the owner the serious danger, but don't be surprised if he just nods his head and continues to use it.
In most cases the owner has an very nice gun that he's been shooting and he see's no reason to stop using it.