Will a 870 stock set fit a 1187?

One is a pump, the other is a semi - one foreend moves, the other doesn't. One has a recoil spring inside the stock, one doesn't

Some synthetic after-market stocks "may" interchange, fore ends.... absolutely not. Fore ends are totally different.

Buttstocks will usually fit within gauge. You may have to drill out the hole slightly putting an 870 stock on an 1100/11-87, but maybe not. I have seen it both ways. Fore ends, no, as noted.
Oh, almost forgot, the depth of the clearance hole at the rear is different, so you will have to stack washers or make a spacer to get the nut where it tightens up.

No. The 11-87 has the tube for the spring that goes through the stock. The hole in the end of the 870 stock is too big too deep to allow the 11-87 stock bolt to tighten up and hold the stock 870 stock in place on the 11-87 spring tube. You can use the 11-87 stock on the 870 if you replace the stock bolt with a longer one and a big washer.

No

Thread Closed.

But the answer is YES. I have done it. Some stocks you do not even have to drill the hole out. You will need a spacer or washers so the nut will tighten. When you put an 1100/11-87 stock on an 870 you need a longer bolt.