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JackFlash · July 14, 2000, 09:16 PM

Hodgdon Data Manual #26 (1994) lists the barrel diameter of 38 S&W as 0.359" and notes acceptable accuracy with loads using 38 Spc bullets varying from 0.355" to 0.358".

BUT, a lighter bullet will change the back pressure characteristics of the load and thus affect the burn rate of the powder. Suggested loads include medium-fast to fast burning powders like Red Dot, Unique, 231, Trap 100, HP38, and Bullseye--the fastest powder on the market.

No 38 S&W cup pressure specs are shown, but the velocities of 145 gr. bullets are in the 500 - 600 fps range.

As a benchmark, in 38 Spc a 148 gr. bullet over 3.2 gr. HP38 generates 830 fps and 11,800 cup. A 145 gr. bullet in 38 S&W over 2.5 gr. HP38 generates 630 fps. Pressure decreases exponentially with load reductions so we might GUESS that the cup could POSSIBLY be somewhere in a VERY LARGE ballpark of 9,000 -- and that's a maximum pressure load with a powder rated number two behind Bullseye for speed.

9,000 cup is very low pressure, and Hodgdon warns that these old 38 S&W chambered guns are both "tired" and not very robust to begin with. A lighter bullet -- even with the faster burning Bullseye -- may not develop the working pressure to ignite the charge cleanly.

You MAY be able to load a lighter bullet and get some increase in velocity with no increase in working pressure. But if you're looking to increase fpe (ft. lbs. energy) at the muzzle, you MUST increase working pressure or bullet weight--not a good plan for a tired old gun.

Muzzle energy is a combination of bullet weight and velocity. Velocity is a combination of bullet weight and working pressure. There ain't no free lunch.

In physics that's not just a hare-brained idea, it's the law.

[This message has been edited by JackFlash (edited July 14, 2000).]

July 14, 2000, 09:16 PM	#5
JackFlash Junior member Join Date: July 8, 2000 Posts: 107	Hodgdon Data Manual #26 (1994) lists the barrel diameter of 38 S&W as 0.359" and notes acceptable accuracy with loads using 38 Spc bullets varying from 0.355" to 0.358". BUT, a lighter bullet will change the back pressure characteristics of the load and thus affect the burn rate of the powder. Suggested loads include medium-fast to fast burning powders like Red Dot, Unique, 231, Trap 100, HP38, and Bullseye--the fastest powder on the market. No 38 S&W cup pressure specs are shown, but the velocities of 145 gr. bullets are in the 500 - 600 fps range. As a benchmark, in 38 Spc a 148 gr. bullet over 3.2 gr. HP38 generates 830 fps and 11,800 cup. A 145 gr. bullet in 38 S&W over 2.5 gr. HP38 generates 630 fps. Pressure decreases exponentially with load reductions so we might GUESS that the cup could POSSIBLY be somewhere in a VERY LARGE ballpark of 9,000 -- and that's a maximum pressure load with a powder rated number two behind Bullseye for speed. 9,000 cup is very low pressure, and Hodgdon warns that these old 38 S&W chambered guns are both "tired" and not very robust to begin with. A lighter bullet -- even with the faster burning Bullseye -- may not develop the working pressure to ignite the charge cleanly. You MAY be able to load a lighter bullet and get some increase in velocity with no increase in working pressure. But if you're looking to increase fpe (ft. lbs. energy) at the muzzle, you MUST increase working pressure or bullet weight--not a good plan for a tired old gun. Muzzle energy is a combination of bullet weight and velocity. Velocity is a combination of bullet weight and working pressure. There ain't no free lunch. In physics that's not just a hare-brained idea, it's the law. [This message has been edited by JackFlash (edited July 14, 2000).]