Charge difference

[DocHolliday]

Gentlemen,
I have a noobie question for you.

If I were interested in going up in grain size from 2F Swiss to 1-1/2 F or 1F in an attempt to improve pattern, how much should I reduce charge and maintain equal velocity?

TIA for replies

 

[Kansas Jake]

I don’t shoot Swiss but if you went from 2f to 1 1/2 or 1 isn’t that a larger grain which in most cases would reduce velocity requiring more powder to achieve the same velocity.

 

[Grenadier1758]

Because the larger grain size of 1 1/2F and even larger grain size of 1 F powders, the charge will have to be increased due to the slightly smaller burn rate of the larger sized powders. I would suggest a 5% increase for the 1 1/2 and up to 10% increase for the 1F. It will really take a shooting chronograph to make the final determination. Use suggested load data for starting loadings.

 

[Old Hawkeye]

Going to a larger grain powder will require you to INCREASE the charge weight to get equivalent velocity. I think you will find 1.5f & 1f are better suited to scaled down cannons than shotguns & other things beside powder choice have more influence on patterns. Better to experiment with powder to shot charge ratio, wads, cards, etc., as my experience indicates 2f & 3f will give optimum performance.

 

[Rock Home Isle]

Gentlemen,
I have a noobie question for you.

If I were interested in going up in grain size from 2F Swiss to 1-1/2 F or 1F in an attempt to improve pattern, how much should I reduce charge and maintain equal velocity?

TIA for replies

You would have to increase your charge is going from 2fg to 1 1/2fg or even 1fg. The larger grain size has less surface area and a slower burn rate.

There are times that I will increase the grain size in my smoothbores, so as to help maintain patterns. Each gun is unique, so you’ll need to play with your loads and test patterns.