I'm trying to get an accurate idea of how much velocity loss you get per inch of barrel length lost. My chronograph is away getting fixed and I'm working on some loads. The loads are for a .219 Zipper. I'm useing .224" 45 and 50 grn bullets and H380 for powder. My Marlins barrel is 20" and the data is all for a 27" barrel. I've heard everything from 30-100fps.

Thanks
Tim

It depends on the cartridge and the rifle but you can usually figure 25-50 fps per inch.

quote:

It depends on the cartridge and the rifle but you can usually figure 25-50 fps per inch.

Yep larger bore faster powder less reduction. More overbore slower powder greater loss because you need barrel to burn the powder.

Ran a zipper in Loadtech using a 40gr and the loss was 125-150 between a 27" and 20"

A little help from our friends here at AR.
http://www.accuratereloading.com/223sb.html

Anywhere between 18 to 55 or even a little more.