I put a sims on my winchester 1300 and now I can shoot winchester supreme high velocity 3" magnum turkey loads all day long. Before I put it on I was cringing after about 4 shots off the bench. I have one on my Encore .375 H&H magnum also. It has synthetic stock and is hollow with no weight to help in recoil. I put a sims on It and it really reduced felt recoil. You can get a prefit sims for just about any major brand of rifle or shotgun which eliminates the grinding hassle. There should be a prefit for your 870 readily available. They also have slip ons if you need one for an oddball stock design. Cabelas has some good prices and their shipping isnt sky high.The cheapest shipping is $6.75.

Heres a link to cabelas for prefit sims
http://www.cabelas.com/cabelas/en/templates/product/standard-item.jsp?_DARGS=/cabelas/en/common/catalog/item-link.jsp_A&_DAV=MainCatcat20712&id=0016465 225373a&navCount=8&podId=0016465&paren tId=cat20811&navAction=push&catalogCode=UF &rid=&parentType=index&indexId=cat2081 1&hasJS=true

Heres a link to cabelas for the prefit pachmayr
http://www.cabelas.com/cabelas/en/templates/product/standard-item.jsp?id=0012755221101a&navCount=20&pod Id=0012755&parentId=cat20811&navAction=jum p&cmCat=MainCatcat20712&catalogCode=IG&amp ;rid=&parentType=index&indexId=cat20811&am p;hasJS=true