40 caliber REAL Data

[Eterry]

If i use 50 cal RB data for a similar weight bullet in a different caliber what will i get?

I can get my chrony out once it dries out and find out for sure...

But my 40 caliber REAL mold throws a 197 grain bullet. The previous owner used 60grs fffg, but idk if he knew the velocity.

Being a 50 cal RB is 180grs would a similar charge of fffg give a similiar estimated velocity?
I plan on starting at 60 grs, mebbe bump up to 70grs and see what kind of accuracy i get.

Im also thinking a wad between powder and conical is a good idea.

Any ideas?

 

[Eterry]

What im having a hard time saying is;

If a 180gr 50 cal rb with 60grs fffg is approximately 1600 fps, would a 195 gr 40 cal REAL with 60grs fffg be close to the same velocity?

That's my question.
Thanks

 

[Zonie]

I don't have any data to support it but IMO, the answer is no.

Using the Lyman Black Powder Handbook & Loading Manual information I see some things that are similar weights fired in different size bores with the same powder loads and the velocities are not similar.

For instance, a .36 cal shooting a 125 grain bullet over 60 grains of Goex 2Fg = 1757 fps
A .36 cal shooting a 125 grain bullet over 70 grains of Goex 2Fg = 1870 fps

A .45 cal shooting a 128 grain patched roundball over 60 grains of Goex 2Fg = 1614 fps
A .45 cal shooting a 128 grain patched roundball over 70 grains of Goex 2Fg = 1691 fps.

It's really a lot more complicated than this because so many things come into effecting the velocity of the projectile with any given powder charge but just generalizing, the velocity from the smaller bore will generally be higher.

 

[Eterry]

Thanks Zonie, i knew it would not be exact, but might give me a starting point.

If it hadn't rained almost 2 inches today i was gonna try and dust off my Chronograph and get some proof.

It's not as easy for me to get velocities with black powder...i have to set the screens farther away.

If i lived on the farm I'd set it up in the yard and shoot off the porch...i miss those days.