On a max charge you'll be about 250fps down with the 20" vs. the 26." with 250g sabots. On 100g charges and 300-350g sabots... more like 150fps or less. I use 55g, yes 55, of 777 ffg, 335g LBT's in sabots for 1250fps, or so, Makes for .454 like performance and won't split your eardrums. 240lb Russian Boar, intact, made a high, high double lung at 35yds, he ran 30yds before his legs gave out by 35 he was on his side and out.