Some details
There are no special action springs that I know of for different loads. All 1100 and 11/87 use the same spring up to and including the .410 1100.
Ditto on proper assembly of gas rings, with a good o-ring and a clean port. Magnum barrels have one port, and almost all 2-3/4 barrels have two (duck/goose barrels to shoot high brass only had one)
There are not a batch of parts to change to make a magnum function not like a magnum, and then convert back to magnum, except to swap to a standard barrel that you would change back to return to magnum status.
By the way, with the amount of shooting that you have through the mechanism, I believe that wearing of the parts is more likely to add drag than smoothness, since I smooth many types of actions for reliability for hunting and defense and see (and remove) the burrs etc. that have developed.
Magnum guns have a few parts different that are obvious, and a few that are not obvious, and a lot that remain the same. Barrel ports, chamber length and ejector position may be unique, and the action bar sleeve is different. The use of a 2-3/4" barrel should work without a hitch, if you had one to borrow and test.
It is possible to rework the existing barrel for light loads, and there will be extra pounding on the gun if you do not follow my recommendations for firing heavy loads after modification.
There is not nearly a reason to panic if a few magnum shells were to be used. Think about this for a moment- an 1100 standard is expected to digest anything from a light 7/8 oz. load (12 ga.) up to a magnum turkey load at 4 dram 1-5/8 oz. without necessarily being injurious to the mechanism. That is why I have no problem with converting 2-3/4 stuff to occasional magnum use, especially with certain advice for obviating pounding. There is actually a case for lessened pounding with a proper magnum conversion than with typical "baby magnum" pounding in an unaltered 2-3/4 gun.
1100's are similar to 11/87's, but cannot be used for operational comparisons of use with varying loads. 11/87's have been known to fail with light loads, but not to the extent of 1100 magnums. 1100 standard guns will be normally more reliable with light loads, and if you have very little chance to shoot magnums anyway, I never recommend getting a gun to shoot a big shell once a year, and light loads the other 364 days. If I need a load of driveway gravel once a year, I don't want to be stuck using a dump truck to go to the store the rest of the time. There is always a price to be paid for multi-use objects, like a mountain climbing running shoe. Make up your mind about the most used aspect, and tailor for that as closely as you can, if possible within reason and budget.
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