I've never used CCI #10 or Remington #11. Remington #10 have fit all but one of my Pietta Remingtons and the one that takes #11 has what looks to be stainless nipples in it. Now my Pietta 60 took #11 CCI right out of the box. That's the only gun I bought new that I can say for sure takes #11 but I have heard other people say their 60's took #11. I've also heard that Italian nipples are hit or miss as to size. I dunno.
You can get Ampco nipples for either size caps.