Some things to consider, some people won't read warning labels. Make them as big and colorful as you like, but still, some will ignore them. Another thing is with handgun reloading in particular is when most of the ''old'' data was figured we/they were using lead bullets to reload our handgun ammo exclusively. Another thing is, some cartridges which we view as ''modern'' really aren't, many preceding the First World War, (none of our magnums certainly) when steel and design weren't up to modern post WWII standards.
With a handgun I have two things I look for above all when loading, accuracy and bullet performance. In my old S&W M&P .38spl. a load of 4gr. Bullseye under a 158gr. bullet is as wild as it gets and rightfully so. It's reasonably accurate and bullet performance is about as good as it gets in the old gal, so be it.
I don't currently own a .357 Magnum, but my last one was a S&W 4'' M-28 and the load I liked was a 125gr, JHP at around 1,450fps. Easy to get in a longer barrels with slow burning powders, not so easy without going into the red zone with faster powders in a short barrel. In my .44 Magnum, S&W 4'' 629-3 the revolver I carry most, I don't feel a need to ''go over'' published data with an RCBS 250gr. Kieth bullet, 1,150fps is fine. My .45 Colts are ancient and I load accordingly, a 1898 Bisley and a 1904 New Service.
Where I get some fingers shaken at me is with my .38 Super loads in my custom built Colt Gov't Model. It's a Colt in slide only, (new SS series 80 slide) the frame is SS also and of the Para ramp type. The mainspring is several pounds heavier which retards the slide slightly and is fitted with a ''Fire Dragon'' recoil management system and a 20lb. recoil spring. The loading is what I expect from a 4'' .357 Magnum, a 124gr. Hornady Xtp at just over 1,450fps. RED ZONE? Nope! It's a standard load using VV N105 powder. Point is, most of the old loadings can be safely reached with newer powders we have today. The old 130gr. FMJ load for the super at 1,310fps now dumbed down to around 1,200fps from the factorys? Yes, with several modern powders the old 130gr. automobile perferator not only reaches the old 1,300fps line, but goes all but 1,400fps! (1,388fps-VV N105 1,385-IMR Blue-published) You have to dig a little for the new powders, but pre-dummed down velocities can be reached or extended safely in published loads.
Where I might really get scolded is in my 7mm Mauser rifle loads. I ignore ''modern'' data developed for the old 1893 Spanish Mausers in mind. I don't own an 1893 Spanish Mauser. Mine are modern Interarms Mark X and Winchester M-70 rifles. Why would I restrict myself to load data for old soft steel rifles? I use data from my Ideal/Lyman manual number 39, (1953) which used a Winchester M-54 and clearly warns the loads are NOT safe in a Spanish Mauser. There we are, those people who ignore warnings, or don't read them. I get 200-250fps faster than any modern published manual provides for the 7mm Mauser.
The purpose of this rant is, you can get your old ballistics and then some with some of the newer powders, use the old data, which seemed to work fine in the day, or venture out on your own and take your chances. Experimenting is fine, long as you know the gun's limitations and load accordingly, I'm not going to risk a fine antique Colt Bisley with any smokeless load no matter how mild. I'll push my .38 Super and 10mm to near max with the new powders though, as well as my 7mm Mausers with the older powders knowing the ballistics in the new strong actions will hold as well as a .280 Remington.