I talked to a Remington rep at a dealer show .
He said it is ok to shoot Hevi shot out of the lead only extended tubes .
The reason for the new tubes is that
1 they want to cover their butt
2 they want to sell you a new tube

I have used factory and reloads out of my 11-87 with either a Rem extra full tube ,super full straight rifled tube or a Under Taker tube .

I have shot several hundred shots over the years patterening ( I made a shot trap and reuse the Hevi shot) and hunting with no problems.