Going from Swiss 2F to 1 1/2F

Been using Swiss 2F in my bench rifle, going to give Swiss 1 1/2F a try. In making this change is there a general rule of thumb on how much I will need to increase the powder charge to get the same velocity? Is this something that is just trial and error.
bob

In theory, a little more powder. In practice, have to find the charge that gives the best accuracy. I’d start with same amount of powder and see how it shoots.

I was thinking it was going to take trying to see what gives the best results. Thanks and have a great day.
bob

A measure cut to hold exactly 100 grains of Swiss 1 1/2F by weight holds only 94 grains of Swiss 2F. In .54 and .58 caliber muzzleloaders I built, more than 100 grains of Swiss 1 1/2 will give hard fouling at the breech. I make weight-corrected measures for each powder brand and granulation and weight, and here are the results for a .54 Kit Carson Hawken I made, 100 grains by weight for each measured powder and .530 balls: Olde Eynsford 2F, 1765 fps, 39 spread; OE 1 1/2F, 1784 fps/17; Swiss 2F, 1888/66; Swiss 1 1/2F, 1724/120. I have found Swiss 2F to be a wonderful powder, but Swiss 1 1/2 Is nothing special for me. Here are targets with a Bridger Hawken I built, after fitting a new sight I made. . Olde Eynsford 1 1/2F is a much better powder, based on hundreds of targets I have shot and loads chronographed. In fact, I just wore out my Oehler 35P for the second time, have to send it back to be rebuilt. This 120 grain load is just a test of that 1"in 48" twist, I use only 100 grains for deer hunting.

Bob, just give it a try. I went the other way, switched from 1.5 to 2 a few years ago.

We should get together and shoot sometime.

Fleener

Art
I would really enjoy getting together some time for a relaxing shoot. Take care.
bob

Herb
Thanks for the info of your testing. Will probably get back in touch with you on your testing. Have a good ay.
bob