This may not be very relevant but I will add it.
When I built my 557 NE out of a H&R Handi Rifle and was developing a load for it I used N550.
I got much help and support on the project from the late Ed Hubbel. He was adamant that I use N550 powder mainly for its pressure curve which reportedly is not as steep or "sharp' as many other powders. ( think that is true for all the N5 series powders but I am not absolutely sure. )
Ed recommended N550 with its "friendly" pressure curve for the sake of my relatively weak Handi Rifle, compared to a real heavy duty DG double rifle, and it ended up killing cape buffalo well with 115 grains of N550 pushing a 700 gr. Peregrine bushmaster bullet at about 1,800 fps. out of a 26.5 inch barrel. ( That is about 100-200fps slower than common modern 577NE loads). It has a lot of recoil for the mild load and a huge muzzle blast but I am used to it and have about 120 reloads good to go.
I have a 50-110 switch barrel for the same rifle and for a TC Encore with a 50-110 barrel. I load N540 for both of them and I like it. ( That cartridge is also a cape buffalo killing s.o.b.)
Brian
