Loaded some 38-40 yesterday in the garage for an inherited Colt SAA made in the 70's. I had some 40 caliber Hunters Supply 180 LRNFP for development loads. I referred to the Lee manual and saw a limited amount of load data with the listed powders being Unique and Bullseye. I decided on the Bullseye load since I had more of it.

The recommended range was 4 to 6 grains with 6 being around the max. We picked 5 grains. It shot great and hit the steel(didn't try it on paper or from a rest).

Brought out the chrony and realized we were only around 500 fps! A look at the Alliant site shows a max of 5.3 grains for Bullseye with a similar bullet at a much higher velocity. I'm not used to this type of result with my other calibers and guns and I know that there are tons of variables involving pressure and velocity. Did some trusted rounds with confirmed velocity data through the chrony out of other guns to rule out chrony problems.

I've just never seen such a drastic difference.Any ideas or tips? Going to try some Trailboss since I have some of that here.

Lots of things affect vel, especially in a revolver. The cyl gap, the exact bore dia. I have a buddy that has an old gen2 Colt, the bore slugged 0.402". So a 0.401" bullet is rattling down the bore. Result, poor accuracy & low vel. I made some 0.403" lead bullets for him & now it hits what he shoots at & vel bumped up.

BTW, the reason data is so conservative is for all those old black powder frame Colts out there.

The Lee manual may be part of the problem. This is a case where older reloading manuals come in handy.

I have been loading/shooting 38-40 for many years. I shoot it out of a 1905 Colt SAA, and a modern USFA SAA. I really enjoy this caliber. I have stuck with the 180gr LRNFP bullets, as they perform well for me in my guns.

For years I loaded the 38-40 brass with Unique, but loading "soft" rounds for my 1905 Colt lead to pretty dirty rounds. For the last year or two(maybe three), I have been using Trail Boss powder, and an really pleased with this combo....accurate, soft shooting, and shoots clean. To me, that is a win-win.

Looks like I forgot a basic pre-step....slug the bore and measure the throats

Thank you all and I'll follow-up with my results. Any excuse to go shooting!.

Oh yeah, especially with the .38-40

Could be .425", could be .427", could be .430"

I worked n two Ruger's that were .423"
(throat diameter that is, no idea what the barrel was, knowing Ruger .430" No wonder the poor guy's guns wouldn't shoot)