Remington lost a great deal of money, little of which made it to purchasers of their products, with the AISI 1140 Modified barrel experiment. The index case was a USED (as in second hand sale) 1100 Trap admittedly shot with reloads.
Loitz vs. Remington Arms, 1990
http://law.justia.com/cases/illinois/supreme-court/1990/68367-7.html
Garza Class Action
http://www.gunsmoke.com/guns/rem_lawsuit_intro.html

Of course personal injury lawyers go where the money is, but we should all consider:
1. Sell a barrel to Bubba
2. Who tries out some home chamber and barrel work
3. Tests his handiwork...barrel ruptures...junior get a piece of shrapnel in his forehead. Somebody's gotta pay now for lifetime care.
4. Personal injury lawyer 'splains to Bubba's relatives on the jury that the barrel was unsafe because of the modifications THE SELLER MADE.
5. Seller has no record of measuring bore or wall thickness.
6. Seller loses suit.

Seems like $120 for a wall thickness gauge would be a pretty good investment in today's world. Europe and the UK have CIP to set wall thickness standards. We let juries do that, based on expert testimony.

"As is" in real estate, cars, boats, etc. means there is no warranty. It doesn't mean the seller is free of responsibility for selling something he knew, or should have known, was intrinsically unsafe. Shotguns are hazardous (duh), but not intrinsically unsafe when used as intended.

Dealers of second hand guns do have an implied warranty of fitness of use of the product. I've never seen any gun dealer use the "as is" language; some clearly state "wall hanger not to be shot". And then there is ol' ed wink

Seller is not responsible if Bubba tries a 3 1/2" turkey load in a 2 1/2" chamber classic double because the product was not used as intended/designed. A hardware store isn't liable if someone purchases a piece of pipe and then makes a pipe bomb.

Sorry Mike, but too many dealers are, in my opinion, way too casual regarding wall thickness measurements, and in 2017 barrel value is highly dependent thereupon.