Why are .357 Magnum and .38 Special related?

They share the same bullet diameter (.357 inch) and the .357 Magnum was developed from the .38 Special case. This makes .38 Special safe to shoot in .357 Magnum revolvers, but not the reverse. The longer case and higher pressure of .357 Magnum make it incompatible with .38 Special cylinders.

Can I Shoot .357 Magnum in a .38 Special Revolver?

Q: Can I shoot .357 Magnum in a .38 Special revolver?

No. .357 Magnum should never be fired in a revolver chambered only for .38 Special. The .357 Magnum cartridge is physically longer and will not fully chamber in a .38 Special cylinder. Even if it partially chambers, the pressure of up to 35,000 psi vs 17,500 psi for .38 Special would be dangerous.

The Physical Barrier

It Won't Fully Chamber

The .357 Magnum case is 1.290 inches long. The .38 Special cylinder chamber is designed to accept a maximum case length of 1.155 inches. The .357 Magnum case is 0.135 inches too long to seat fully in a .38 Special cylinder.

When you attempt to chamber a .357 Magnum round in a .38 Special revolver, the cartridge protrudes from the cylinder and prevents the crane from closing. The cylinder will not rotate to align with the barrel. The revolver cannot be placed into battery in the normal sense.

This case length difference was a deliberate engineering decision when the .357 Magnum was introduced in 1934 — specifically to prevent .357 Magnum cartridges from being chambered in the millions of .38 Special revolvers already in service.

Why the Pressure Numbers Matter

Double the Design Pressure

If .357 Magnum were somehow discharged in a .38 Special revolver: the 35,000 psi peak pressure is approximately twice the 17,000 psi SAAMI maximum the revolver is designed for. Cylinder walls are not rated for this. Catastrophic failure — cylinder rupture, frame damage, injury — is the expected outcome.

Specification	.38 Special	.357 Magnum
Max Pressure (SAAMI)	17,000 psi	35,000 psi — 2× overpressure
Case Length	1.155 in (cylinder max)	1.290 in — too long by 0.135 in
Overall Length	1.550 in	1.590 in
Bullet Diameter	.357 in	.357 in

Design Context

Why This Relationship Is One-Way

The .38 Special/.357 Magnum pairing is an example of intentional one-way compatibility in cartridge design. The shorter cartridge (.38 Special) fits in the longer chamber (.357 Magnum cylinder). The longer cartridge (.357 Magnum) does not fit in the shorter chamber (.38 Special cylinder).

This is the same design logic used in several other revolver caliber pairs: .44 Special in .44 Magnum, .327 Federal Magnum in .32 H&R Magnum, and .45 Colt in .454 Casull. The "parent" cartridge — the lower-pressure, shorter round — is always safe to fire in the "magnum" revolver. The reverse is never safe and is physically prevented by the length difference.

If you own a .38 Special revolver and want to use .357 Magnum, the answer is to acquire a .357 Magnum revolver — not to modify or force the ammunition.

Bottom Line

Do not attempt. The cartridge will not chamber correctly, and if somehow discharged, the pressure is approximately double the revolver's design rating. The case length difference is an intentional safety feature, not an obstacle to work around.