Thanks for your comments eagle27. I wish I had discovered these rifles years ago and now had your level of experience with them. I measured the twist rate and it is 1:12.
I've been doing a lot of reading about these rifles and I think the 54j has gotten some unfair press compared to the "improved" models like the 65 and 68. The rifles were changed for the American market but how much were they really improved.
The cock on closing is no problem at all. It felt a little different at first but I am now already used to it. No issue.
The single stack magazine works great. There is no where for the rounds to go and get out of alignment. Each and every round comes up directly under the bolt and pointed directly into the chamber. And I haven't noticed any pregnant belly aspect to the stock that some have observed.
I guess, in the interest of science, I will have to get one of the newer models and see for myself!