1100s have a slightly smaler extractor claw than 1187s and the gas system on the 1187 self compensates for both 2 3/4 and 3 inch shels on the 1187 premiers and Sp models. the sporting clays 1187s have a 2 3/4 chamber and i think a diferent gas system to the 1187 premiers basicaly the same as the old 1100.
The old magnum 3 inch 1100 was a devil to cycle lighter than 1 1/8th oz loads some would but many did not like lighter loads.
The 1100 allways felt nicer in my hands than the 1187 of the same chamber. i once had a 1100 magnum and a 1187 sp in timber( so cant blame symthetic) and dispite the 1100 having a 30 inch multichoke barrel with a Hastings turkey choke screwed in the 1100 it felt a lot nicer to handle and it was livelier in use in the field to boot.
The big + for the 1100 and the 1187s is the fact that one size fits all people if you are green as grass with a shotgun you can bet your life you will fare better with a 1100 series than lets say a Benelli or Beretta. Well thats how it allways seemed to me
1100s/1187s have a few faults the lock time is slow there is no getting away from this it is in the nature of the beast, it is of little significance but none the less it is a fact.
They have a few mechanical features that do give issue on hard worked/ abused examples, notable of the faults is the infamous intercepter latch circlip fault
this feature is a nuisance and as the grove wears the circlip begins to ride off and you are broken down as the latch leaver gets away
A new leaver and clip may cure the problem but in the end it will be away again and it will become a big problem. There are ways around this aplenty but all are a faff and in my view the guns worst fault to live with or cure.
The action bolt forks/ bars do buckle and deform and jam up and on ocasion the mag spring tube can come out of the action rear, it is just a press fit in and is a budge to sort out, the gas seal can give issue but it is the easiest fix on the 1100s and realy not worth the mention.
Do i like 1100s/1187s ? A Big YES! They are a wonderfull gun a true classic let down of late by crude finish on the SP models and not helped by being upstaged ( well mabe out marketed) by the italian B guns they have lost popularity, but you cant take anything away from the Remy it is there and it has the shirt, it will come good in the end. I can remember when the old A5 Brownings were knocked for being old hat but there are still loads out there struting there stuff and the exact same for the 1100s/1187s.
My choice of 1100/1187.
A late model multichoke 3 inch Magnum 1100 with 30 inch barrel a real nice goose stroker load it with a 1 3/4 oz Bismuth load and a Hastings choke
Hell! i want one just thinking about it.