Home Forums Reloading Shotshells - TSS and Unleaded TSS shotshell compatibility

My question is about the .410 load of TSS #9 shot. Spoke with Federal customer service about tungston shot compatibility in older shotguns. All he could tell me was the ammunition was compatible in something like "modern firearms in good condition." And all he could say further was that with the full length shot cup/wad it would "probably" be OK but the decision is left to the customer. Danger being possible scoring of the barrel if the shot wore thru the shot cup. I've seen numerous examples of users running the ammo in less than current single shots and I've seen no report of barrel damage. But the little Ithaca drop-lever single shot I'm thinking about does not need to be ruined. It's the gun my father in law gave my wife when she was 12 or so. Hell hath no fury comparable to hers if I damage that shotgun. So, anybody actually checked the barrel of their older .410 after shooting TSS?? Another gun that might be used is a TC Contender pistol in .45/.410. "Choke" adapter is a threaded 2" or so straight rifled piece with heavy lands to stop the spin. Interested in any first hand information there as well. Thx