From the JP Rifles instruction page used without their permission:
The key to reliability with the 1100/1187 type shotguns is two-fold. FIrst, use only factory ammo with high port pressure that you have used extensively in practice and verified its reliability. Don’t use reloads or some cheap promotional loads not designed to cycle semi auto shotguns. For example, if it says something like “dove and quail” or “Squirrel and rabbit” on the box, and sells for $2.49 at Walmart, don’t use it. If you’re looking for some cheap practice ammo, try Federal High Velocity Game 7/8 OZ loads at 1400 FPS (Fed HVG 12). Walmart usually has these for about $3.50/box. I’ve found that they are quite reliable and have enough port pressure to give a quick cycle on the gun which results in a snappy feel that we’re looking for. The important thing is to verify the reliabiltiy of any ammo you wish to use at a match before you get there. For example, not every ammo that happens to say 1 1/8 ounce, 3 dram equivalent on the end of the box will cycle the gun. The port pressure may not be adequate in a ported shotgun. If you can’t travel with your ammo, ship it to a friend or make sure you can buy something that you absolutely know works in your gun when you get to the match. Second, proper maintainence is essential for the Remington 1100/1187 shotguns. The most important maintenance item is keeping the outside of the magazine tube clean. After every match or shooting session, remove the barrel and forend. Slide the gas rings off of the mag tube and with the action in the locked open position, remove the fouling from the outside of the mag tube with an oily rag. If it has become encrusted, a piece of ScotchBrite may be needed. Clean any build up in the gas collar and pistol travel area off with a solvent and piece of fine ScotchBrite if necessary. Failure to remove the residue from the outside of the mag tube results in the build up getting very hard and stopping the piston assembly from sliding freely on the tube. Run the tube dry or lubricate with powdered graphite for actual match use but store with an oil film when not in use. Every so often is is also necessary to clean the inside of the gas collar using the same method. The action and barrel do not have to be cleaned as often, however the chamber will accumulate a build up of plastic wad material and powder residue which should be brushed out to insure the cartridges easily go into battery.