Rivelling (a series of rings on barrels) can be bad news. This can result from several things. Once more common than it is today, it was typically caused by over-oiling bores and then not properly cleaning out the gun’s bore with a patch before firing it. The wad would then scrape the oil from the bore as it accelerated down the bore, creating a circular ‘wave’ of oil ahead of the wad. The oil could not accelerate at as fast as the wad and shot load, so the wad would overtake the oil exerting pressure outwards and creating a series of bulging rings along the barrel. This is more unsightly than dangerous, but it is still something to look for and avoid.
Do not confuse rivelling with poor striking off of the barrels. Some cheaper guns were less well finished than the majority are today. Fast production with little time spent on hand checking and finishing barrels meant some appeared to be rivelled from new! It is easy to diagnose the cause of an undulating barrel by looking inside the bores. If there are no corresponding ring bulges visible in the bore, then the explanation is just poor striking off.
You will also notice some dark rings in the bore. These are not faults in the gun. They merely show a change in bore size. In fixed-choke guns the most obvious of these will appear close to the chokes, where big changes in diameter produce several rings close together. There also may be some rings ahead of the chambers and along the bore.
Barrel straightness can be checked by painting a crisp dark line on a skylight or similar. This check is done whenever a gun is made. The black line puts a thin, dark shadow line along the entire bore. If line is straight, so are the bores; if it’s wavy, the barrels need to be be straightened… or scrapped if the problem is too severe. You may like to check for this too, but it shouldn’t be required. Problems here should have shown up when the gun was manufactured.
All this should have given you an insight into how to inspect an older gun that you’re sizing up as a potential purchase. Discover how the quality of some of the older big name guns stands out a mile compared with spending a similar amount on a new gun manufactured to sell for around the same price. In my book, there is no real choice to be made; it is, as the youngsters might say, ‘a no-brainer’!