Jammer six,For me and my Lee handheld primer seater, The winchester primers are BY far easier to seat with 1/2 the pressure needed than federal so im guessing its the hardness thats a factor,or either that your crushing the winchesters to much(just a maybe)..I agree ,stick with what works best for you(federals worked great for me as well),but I dont think its the primers themselves.It could be the brass im using is just slightly larger in the primer area as well so I have to admit that could be a factor with my experience.It always takes more force for me to seat federals, so that is why I had my 5-6 missfires(I didnt seat with enough pressure
) IMO.After I seated with more force I did not have one missfire with the 500 or so federal primers I had left.