This gun, with this barrel, just always works. I expected to find something broken when I got home, but everything was whole. I pretty much get the impression different runs of ammo use different powders. Maybe this powder/charge combo is on the wimpy side. Geez, I have another flat plus the rest of this flat. Maybe no more doubles with them, and I'll have to carry some green shells for my first shot on doubles. Hey, I like green, but these Estates I won.
If your 1100 is a true trap barrel/receiver combination, all things equal, it should work fine with 1150/1250 fps 1 oz loads. If you're using a field barrel and/or receiver which are generally set up for hunting loads then it's quite likely that your 1 oz load may not work reliably. One thing you could do is pick up a box or two of the promo 1290 fps 1 0z loads (usually Federal field loads) and try them....at 1290 fps it's usually enough to make hunting guns work. Try it and see, if they work you may want to have someone enlarge the gas ports (one at a time)and your loads will probably function as well. You might note that in the literature that comes with 1100 target models they don't recommend using hunting loads in them. Too much pounding they say.
Just my thoughts with my three 1100's with many, many rounds through them.
I've never had trouble in any of my 1100s with Federal ANYTHING. I clean and lubricate it, plus I replace the usual wear parts at regular intervals. It is entirely possible that it's a batch of shells that has something different about it that does not work well in your gun. Sometimes a different lot of powder, setting for the head diameter, etc. Get a different lot of ammo and trade off the rest.