As a shooter/handloader of some 50 years, I feel a mite dumb asking this, but here goes;
I frequently read references in handloading threads to Clays, Universal, and Universal Clays. Are these all the same powder?
No they are not. Visit the Hodgdon's powder website for full information about that family of powders.
Clays was the first to be introduced and is the fastest-burning of the three. It also is one of if not THE cleanest-burning powder available today. Clays International and Clays Universal are slower-burning and require near-maximum charges to generate enough heat and pressure to burn completely in handguns. They started out as shotgun powders but all three have also become popular handgun powders.
Regular Clays is the only powder I use in my revolver target loads as it is as accurate or more accurate than any other I've tried and doesn't leave the gun and my hands a sticky mess. It also works well in 1911s of almost all calibers but AutoComp, which doesn't burn completely in my revolvers (I guess due to the barrel-cylinder gap bleeding off pressure), works best for me in my .38 Super and .45ACP although the velocity and felt recoil are higher than with Clays.
I understand Clays powders are a little hard to find right now in some areas due to a fire or something in the plant where they are made.
For years I loaded 45 Colt with 6.7 grains of WW231 on a Dillion 550B press. When I started loading 44-40 WCF I didn't want to use that fast of load. I found that Clays in the same setting gave me 4.4 grains, and this is my 44 WCF load to this day. When I set up to load one of those cartridges, afterward I switch the tool head and powder and load the other. Saves the frustration of calibrating the powder measure. Ivan