What 'old manuals' do you have??
The only reason you would ever need Magnum primers in a .222 Rem might be for use with some ball powders that are harder to light off.
My older Speer manual for instance only show mag primers (noted by an *) with a very few types of ball powder.
But, regardless of all that.
.222 Rem data is .222 Rem data, regardless of barrel length.
Use what you have, with the primers you have.
Then start at the Start load and work your way up.
rc