I fire 38 Long Colt in my 1899 from time to time, milder than 38 Special and lead round nose bullets. I will not fire any jacketed ammo in mine. As a matter of fact I shoot maybe two cylinders a year through it.

The early guns do not have a forcing cone as we know it today, and any slight misalignment of the chamber to barrel sends the bullet colliding with the edge of the barrel and can lead to a cracked barrel, in my opinion.