In my 2.25 in bores, I use 3.6 ounces of 1F for blanks, and up to 3 ounces of cannon grade for live charges. I am a bit on the conservative side, but only by 10%-20% or so I think. I see no reason to push things, as I am getting what I want with slightly conservative charges. 3 ounces of cannon grade for a live charge is alot by the way.... it is a safe load I believe, more would be OK as well, but it is crankin .
His recommended blank load sounds a bit stiff to me. Even throwing out my conservative nature it seems alot to me. How often did he shoot it, an how is the barrel constructed?