All common shotshells, from the earliest blackpowder loads to the latest you'll find on the shelf today are loaded to a limited range of peak pressure - generally between 6,000 and 11,000 psi. The problem with some vintage guns originally made for black (or semi-smokeless) powder is that they were designed to contain these pressures only in the first few inches of the barrel, not farther from the breech. The finer grades were often prized for having light, thin barrels that gave them superb handling characteristics for upland bird shooting. While thin barrels were fine with the quick-burning black, semi-, and most early smokeless powders, they are more likely to fail when used with modern progressive-burning powders that may produce the same pressure but sustain it longer - and therefore farther from the relatively thick barrel walls near the breech.

Since we seldom see pressure figures or powder specs on factory-loaded shotshells, it's not usually possible to know for sure if they will be OK in a vintage gun. The solution is careful handloading, selecting loads that use relatively quick powders (Red Dot, 700X, etc.) and are listed by the powder manufacturer with peak pressures at the low end of the spectrum.

Here's one example from Alliant's website -

(2 3/4" WW-AA hull)

Shot Wt.(ounces) - Velocity(fps) - Primer - Powder - Wad - Grains - Approx. psi

1 1/8 - 1,090 - Win 209 - Red Dot - CB 1100 - 16 - 8,000

The same powder charge, but with 7/8 oz. of shot and an appropriate wad, will give about 1150 fps at around 7,000 psi and does the job at skeet or 16-yard trap when pointed right.

Handloads in this class are less likely to damage vintage shotguns than are loads of unknown pressure characteristics or handloads with slower powders and/or higher peak pressure.

Semi-smokeless powder was a mechanical mixture of mostly black powder and a fairly small proportion of nitrocellulose. It was useful because it could be loaded bulk-for-bulk with black and had similar ballistic properties but left significantly less fouling in the bore.