Let assume he has a 10 gauge,what was the reason they gave for not shooting them? Before the advent of plastic,guess what shotgun shells were made of? If they were kept dry there should be no reason not to shoot them. The worst that could happen is they are duds.
Not likely though. The stuff people make up, I made the mistake of calling Bensons about a gun, the next thing I know is the salesman is telling me I can not buy a 9mm barrel and use it in a 40 Glock or 357 sig Glock. I was inquiring whether you could do the same with a 40 shield.