As a happy GP100 owner in .357 (first gun that I purchased), buying one in .38 special will take the punishment of hot commercial loads such as Buffalo Bore. As several have noted above, some police departments were not allowed to issue .357 Magnum revolvers due to public pressure. Ruger then easily downgraded the .357's to .38 special for these agencies.
As far as the current production, believe it is a special run for one or another of the major wholesalers such as Lew Horton, etc. If you are concerned about whether or not these cylinders will handle .357 then I advise you to either call Ruger customer support or the wholesaler for an answer. My guess like others above ( and I stress guess) is that with the whole lean manufacturing practices at Ruger that has been reported that a separate .38 only cylinder with different heat treatment is not the way that they do things especially on a special run basis.
As far as reloading really hot loads in regular or even +P .38 brass approaching pressures of even light .357 rounds, why would someone want to do such a thing? The brass is really not designed to take really high pressures and it would probably give way before the GP 100 would. At best, it would shorten the life of the brass and at worst maybe damage one's gun or one's health. If you want .357 level loads, then use .357 brass and buy a .357 version. .38 brass is simply not designed to operate at really high pressure levels.
One last reason not mentioned for buying a .38 version is that some people believe (I'm agnostic on this one) that firing .38 specials on a continuing basis in a .357 revolver degrades the accuracy through spalling, dirt, amount of free bore, etc. in the revolver's chamber. What I do know is true is that you will need to make sure to keep your chamber clean if you want to fire a bunch of .38 specials and then chamber .357s for social purposes. Crud built up can prevent easy extraction of the .357 brass or even prevent chambering in a very dirty revolver.
As far as the current production, believe it is a special run for one or another of the major wholesalers such as Lew Horton, etc. If you are concerned about whether or not these cylinders will handle .357 then I advise you to either call Ruger customer support or the wholesaler for an answer. My guess like others above ( and I stress guess) is that with the whole lean manufacturing practices at Ruger that has been reported that a separate .38 only cylinder with different heat treatment is not the way that they do things especially on a special run basis.
As far as reloading really hot loads in regular or even +P .38 brass approaching pressures of even light .357 rounds, why would someone want to do such a thing? The brass is really not designed to take really high pressures and it would probably give way before the GP 100 would. At best, it would shorten the life of the brass and at worst maybe damage one's gun or one's health. If you want .357 level loads, then use .357 brass and buy a .357 version. .38 brass is simply not designed to operate at really high pressure levels.
One last reason not mentioned for buying a .38 version is that some people believe (I'm agnostic on this one) that firing .38 specials on a continuing basis in a .357 revolver degrades the accuracy through spalling, dirt, amount of free bore, etc. in the revolver's chamber. What I do know is true is that you will need to make sure to keep your chamber clean if you want to fire a bunch of .38 specials and then chamber .357s for social purposes. Crud built up can prevent easy extraction of the .357 brass or even prevent chambering in a very dirty revolver.