It is not and will not be an 11/87 barrel, they are not and never have been interchangeable.
If you are sure it is the barrel that came from the factory you can always call Remington with the serial number and they can tell you exactly what barrel you do have, when the gun left the factory and exactly what that gun left the factory with along with when the gun was made.
Contrary to Remington's instructions, people do swap the barrels, so your concern is not unfounded. The gas cylinder on the 1187 target barrel has an indented step on the front end of the cylinder (on field 1187 barrels, that step holds the pressure relief mechanism which is not used on the target barrels). Normally there is a separate metal shroud that covers that step, but it may be missing. On 1100 barrels, the exterior of the gas cylinder is smooth, no step. At least that's how I tell them apart, I'm sure someone will correct me if I'm wrong. I was always a little surprised that Remington didn't mark the 1187 barrels as such in some obvious way. I guess that would have been too easy. James Fawcett
I've owned 2 1100s that predated the 1187, and neither was marked on the barrel as an 1100. I've owned 3 1187s from fairly early in the production run, and none of them were marked 1187 on the barrel. Maybe later 1187s and current 1100s are marked. I'd be curious to know if they in fact have changed in that regard. James Fawcett
Just to add. I put once tried an older 1100 trap barrel on an 11-87 The clearance around the extractor was very close since as mentioned the cut in an 11-87 is wider. Newer 1100 barrels have the wider extractor and wider cut. It worked just fine. I was afraid some day some dirt or grime might cause a problem with the extractor so I put it back on an 1100. I have heard some people have opened up the slot a little on older 1100 barrels. In my experiment as mentioned by others, the original 1100 forearm would not fit over an 11-87 barrel, but the other way worked just fine.
Well, I guess that I do have an 1100 barrel. There is no groove around the gas cylinder and the extractor cut appears to be the same size as that on another 1100 barrel that I have. Additionally the older 1100 forearms do fit on it without any problem or interference.
Thanks for the info.
I have been shooting an 11-87 barrel on one of my 1100 traps for some time and it works just fine. I suspect that an 11-87 barrel will work better on a newer style 1100 due to the wider extractor slot. I own many. many 1100's and 11-87 's and none of them are marked on the barrel as to what gun they fit.as far as I know they have never been marked. Jeff
Take a look at the difference in where the O-ring groove is on the 1100 and 1187 magazine tubes. Even though it is differnet ,it still works for me. I have been shooting the older 1187 barrels on 1100's for over 10 years by using a mig to spot weld the gas check band to the barrel so it will not jump off. Remington made the first barrels that way so you could not interchange them because with the 1187 extra metal cap ring that contains the gas band would not let the forearm go on. Now the new 1187 barrels don't have the seperate ring unless they are old stock. any questions I could post some pics. Jeff
two things about the guns in general,make sure the action spring is not fatigued and keep an eye on the bolt buffer. A weak action spring allows the action bar assembly and bolt to act like a slide hammer and can result in the mag tube seperating from the reciever. The cost for a new spring is less than $10 and once ayear can't hurt. Jeff