I remember when a shotgun would fire any shells it was chambered for,with the exception of maybe low powered shells in some old automatics.In the last year I have had experiences with several different problems with the guns or the ammo itself.First 3 brand spanking new guns,one Maverick 88 a friend bought,and two Remington 870 expresses one is mine and the other is my nieces husband.All three fired Remington buckshot and slug loads with no problems,same with some Remington express and Winchester super X heavy field loads.All three then had problems with difficulty ejecting,sometimes you could really pull hard and shell would eject,sometimes a cleaning rod had to be used to knock out the shell because the extractor had ripped through the rim(these were Remington game loads with the black hulls).The other types that have caused extraction problems are Fiocchi's target and the bulk packs of budget ammo bought at wal mart.After looking at several firearms websites it seemed the problem was either dirty chambers,or rough chambers from the factory.All three were cleaned thoroughly cleaned before the first time they were shot so dirty chambers were not the problem.So I took a bore brush wrapped in OOOO steel wool and put it in the chuck of a battery drill and lubed it up good with CLP and cleaned,polished the chamber real good.It worked great on my gun,haven't found any ammo it will not eat since.I the did the same to the other 870 and my friend did the same to his Mav 88 and they are now able to shoot the budget shells as well.I think the problems were a combo of rough unpolished chambers on these lower priced firearms and poor quality control and cheap materials on the low priced ammo.Now the other gun in question is an Ithaca Model 37 that papaw bought new in 1942 and has shot every kind of ammo without problems over the years.I bought some PMC shells and they would extract fine but some were hanging up in the receiver,I compared some fired hulls from some other brand and found out that the fired hull was longer than 2 3/4 inches on the ones that hung up and thats why they were getting stuck.Nothing you can do about that except buy another brand or shoot in a o/u or sxs.The only other shells I had problems with were Winchester AA target shells,out of a box of 25 shells 9 of them had rims that were either out of round or oversized to the point that they would not fit into the magazine tube,the AA's aint really budget shells.I can deal with polishing my own chamber,after all it is a budget priced gun and fit and finish is less than on a Wingmaster thus the lower price.The ammo problems with the PMC and the AA's in the Ithaca though are bound to be quality control problems.Well,if any body here has an 870 express that sits in a closet because it was unreliable,try the steel wool and drill trick it sure worked for me.Thanks to the shotgun guru at TFL and THR.