Fiocchi primers are equivalent to the Fiocchi primers. There are three primer numbers I have had over the years. The 615, which was an oversized primer, the 616, which was a standard sized primer with very little taper, and then the newer 617 primer, which I have yet to try out. They seem to be the same as the 616 in size, but have no idea how they perform, since I have not loaded any or tested any. There is data for them from some of the powder companies. There is no way to make a statement that primer "A" is equivalent to primer "B", unless you were to test them with all possible combinations of components. If using Fiocchi primers, I use data for Fiocchi primers if I want a "known" load.
Making a primer substitution in a load is risky, unless you have data to support it. There are three possibilities with regard to the effect on pressures. The first is that the pressure would remain the same. The second would be that the pressure would decrease. The third is that the pressure would increase. If you get the third scenario, and the increase is substantial, it could put you above established pressure limits. Now the real problem is that the average reloader would have no idea which one of these scenarios he would encounter unless he had pressure testing equipment at his disposal. The other issue is that the primer may do one of the three scenarios in one load and do another in another load. You can't say that primer "A" will always give same/lower/higher pressures than primer "B", since that is what it did in load "C".