Depends on the load
The .40 caliber bullet is a little larger in diameter and is a little heavier (under most circumstances). The .40 will usually have more powder, velocity, and muzzle energy. Also, the .40 is designed for use in a semi-automatic and the .38 is a revolver cartridge.
That will depend on WHICH .38 caliber cartridge (thre are several) the length of the barrel (longer barrels= faster bullets) and the catridge itself. A very light target cartridge will be slower than a hot defensive cartridge. For a .38 Special revolver with a 4 inch barrel, velocity averages about 770 fps, but may range from 670-980 FPS.
Depending on bullet weight and powder, 650-1000 fps or more.
Muzzle velocity will vary, depending on whether fired from a rifle, revolver, or semi-automatic pistol- and on the loading of THAT particular cartridge. A .38 Special wadcutter target load fired from a 4 inch bbl revolver will reach about 690 feet per second. A +P+ (high energy load) fired from a 6" revolver may reach 1100 fps.
38 special.
gunbroker.com
You take it to a gunsmith
No
.38 Special, yes. Other .38 cartridges (such as the .38 Long Colt or .38 Super), no.
38 special is only a revolver caliber. that's like saying a 44 magnum revolver or a 500 special revolver. a revolver is a revolver
No, you cannot.
No, you cannot.