There’s a lot of ‘conventional wisdom’ in the gun world that just ain’t so. Two that come up a lot are ‘Damascus-Barrel Shotguns aren’t safe’ or the variation, ‘Damascus-Barreled shotguns are unsafe with Smokeless loads.’ The other that has gotten a lot of discussion lately is ‘Revolvers designed for Black Powder are unsafe with smokeless loads.’
These claims are not necessarily true or false. The fact is that no one can tell you if your gun is safe over the internet. That being said let’s address these nuggets of ‘conventional wisdom.’
Starting with damascus shotguns the first thing to say is that any antique shotgun should be thoroughly examined prior to firing it, period, regardless of the composition of its barrels. Chambers should be measured for length and diameter, and examined for pits, bulges, rings, rust and cracks. Bores should be examined for the same, using proper instruments. Barrels should be examined externally for rings, bulges etc. The mechanism should be tight and free of cracks. On double-guns the barrels should be rung; a clear tone indicates a solid join between the barrels. Buzzing or vibration indicates separation of the central rib, which might be caused by hidden bulges and in any case is unsafe. There are other things that a good gunsmith can look for, and having a ‘new’ antique examined by a competent gunsmith is highly recommended. A mirror-bright bore in an antique is a warning sign that they barrel may have been honed, possibly to the point that it is too thin to be fired safely. In these cases it is vital to have the wall thickness of the barrel and chamber measured.
Another thing to be wary of is that many guns had shorter chambers than modern guns. 16-Gauge and 12-Gauge were both offered in shorter lengths than the standard 2-3/4 inch we are familiar with today. Shooting modern 2-3/4 inch shells in these guns can result in unsafe pressures, and many older guns have had their chambers rebored to longer lengths, which can result in excessive thinning at the throat of the chamber, which can render the gun unsafe. If you load your own you can load-to-length, so a shorter chamber does not, in and of itself, mean that you should not shoot the gun.
Regarding damascus barrels there is a lot of mythology about them. Some claim that these barrels were never intended for smokeless loads. Given that many manufacturers specifically stated that their guns were safe to shoot with these loads and had them ‘Nitro-proofed’ seems to give the lie to this. To this day the British Proof House will proof a damascus shotgun for smokeless powder.  Damascus Mythology is well worth reading on this topic. The common wisdom- fostered by manufacturers at the time- was that modern steels were superior to damascus. In fact the transition from damascus to modern steel barrels was done less because the modern steels were superior than because they were easier and cheaper to manufacture.
In the early years of this century Sherman Bell did a series of articles in the Double Gun Journal called ‘Finding Out for Myself.’ As part of this series he tested a number of damascus-barreled guns, some of them in dreadful condition, with modern 18,500 PSI proof loads. None of the barrels or chambers burst. Standard 12 gauge loads typically run between 6200 and 13000 psi, with most of them clustered towards the middle of that range. When he tested a damascus gun to destruction it took a load over 30,000 psi to burst the chamber. Typically when antique shotguns burst their chambers or barrels it is because a) the bore was obstructed, b) the barrel was rendered too thin by over-honing or c) an over-pressure hand-load was used.
Now, I am not going to tell you that you can shoot your damascus shotgun safely with modern loads. Some antique guns are safe to shoot, some are not. Some of those antiques have damascus barrels, some don’t. You need to have your gun properly examined before shooting it, period.
One thing I will say- if you have had your antique gun examined and determined that it is safe to shoot you would be well advised to shoot low-pressure loads through it. Not for fear of bursting the chamber or barrel, but because high-pressure loads will accelerate wear on your gun, and it has already had a working life-span or two under it’s belt. Also, if your gun isn’t nitro-proofed it might be prudent to restrict yourself to black-powder (or BP substitute) loads just to be on the safe side.
Now, regarding revolvers designed for black-powder loads the same advice applies. You should have the gun examined carefully before firing it. Check that the hammer locks positively and securely at both half and full-cock. Make sure that the cylinder locks properly in each position, both single and double-action. Ensure that the cylinder-gap is not excessively large. Check to make sure the cylinder does not have excessive end-play. make sure that the bore and chambers are in good condition. Look for erosion of the forcing cone and frame. It really is best to have the gun examined by a competent gunsmith and if there is any doubt don’t fire it, period.
Regarding black-powder and smokeless loads- it’s complicated. Some guns designed for black-powder can be shot with modern loads, some can be shot with some modern loads but not others. This is, however, a highly individual thing, and needs to be handled on a gun-by-gun basis.
That being said guns designed for .22 rimfire, even the oldest, can usually be fired with modern CB caps safely if they are in good condition. These rounds fire balls or light bullets propelled only by the primer, with the sort of velocity usually associated with pellet guns rather than firearms.
Where this question comes up in particular is with guns made during the period of transition between Black and smokeless powder. Specifically top-break revolvers in .38 S&W and .32 S&W (short.) These calibers were initially loaded with Black Powder and spanned the transition to smokeless powder. S&W addressed this issue in a 1909 letter, in which they stated that all of their guns were safe to shoot with factory smokeless ammunition, but caution against using hand-loads. Since this time we have developed a wealth of information about hand loading these cartridges, but during the transition some people tried to replace BP with a similar volume of smokeless powder, with predictably disastrous results.
Modern cartridges sold in this country are loaded to SAAMI standards. Reading their website it is apparent that these standards are designed so that standard-pressure cartridges can be used safely in any gun (in good condition) that is designed to chamber that cartridge. With regard to current factory loadings in .32 & .38 S&W, these are less powerful than the original black-powder loads for these cartridges. On the Smith and Wesson forum many people report that they have fired modern loads in guns dating back as far as the 1870s without any damage to the guns. I haven’t seen anyone there report that they have damaged their guns shooting these loads, either. As long as the gun is in good condition and you are firing the round it is chambered for there shouldn’t be an issue. The exception to this are .38 S&W loads made by Buffalo Bore. These are effectively +P loads, and are designed for good-quality solid-frame guns or Webley top-breaks. They will not necessarily blow up a good S&W top break, but they are not recommended for them and it would be wise to take the manufacturer at their word.
Again, Neither I nor anyone else can tell you if your gun is safe to shoot over the internet, and if there is any doubt you need to err on the side of caution. Again, using low-pressure loads will preserve the life of your antique firearm regardless of the caliber.
In the end it is up to you; you’re an adult. Exercise due diligence and common sense, err on the side of caution and don’t trust something just because you read it on the internet… including this article.