New to the 1100.

Do I need to consider more than the barrel (chamber) for 3".

My 30" barrel is clearly identified for 2 3/4" What else is required for safely doing a 3" ?

When Remington first introduced the 3" Steel Shot barrels they said they were okay for 3" steel loads on 2-3/4" receivers. The are essentially a 3" Magnum 1100 barrel with choke tubes. The only differences between a 2-3/4" and a 3" 1100 are the barrel and the action sleeve. And before anyone says otherwise, the ejection port, the action spring, everything else is the same. The 3" action sleeve is heavier and the 3" barrel only has one gas port. If you put the 3" barrel on the 2-3/4" receiver you will likely have to experiment to determine just which loads will properly cycle the action, and it isn't likely to be light loads, at all. Now Billy Bob may come along and tell you his Uncle's Model 1100 will do so and so, but that doesn't mean squat, because they are all different. I have had several 3" guns and one of them would run with 1-1/8 ounce field loads, but it was the only one that would. Also, the very early 3" Steel Shot barrels had a slightly smaller gas port - steel loads were developing rapidly.
I have swapped around all kinds of barrels, and going with a 3" barrel on a 2-3/4" receiver poses no issues as long as it will function with the shells. Putting a 2-3/4" barrel on a 3" gun and then shooting heavy loads does pose a potential issue because the extra gasses can get the heavier action sleeve going too fast and batter the receiver. Always keep and eye on the buffer and the back of the receiver and make sure you are NOT getting any metal to metal contact and you will be okay.

Welcome to the Remington Owners Forum ModernRifle !!

I myself am a firm believer in using ONLY the size ammo the manufacturer inscribes on the barrel...

...to ignore that spells disaster !!

I agree, but he was asking about a 3" chambered barrel.

Understood...

Thank you Virginian for your reply.
I'm sure that I will be happy with the original 30" 2 3/4" but did see some 3" listed on GunBroker and other sites and was very curious about the platform and interchangeability.