H,

I would suggest you try a variety of shot loads. From what I read, in general, fiber wads are prefeered. That being said I have not found an ideal load for my Evans. Some pattern well, but print low, could be a stock fit thing, but my eyes line up right for the slug sights. The best load I have found to date for my 12 is a Gamebore English fiber loaded 65mm (2 1/2") shell. They make a 20 ga 2 1/2" fiber load in British shot sizes (you want 6's), loaded to British pressures. They sold direct to me since there was no dealer nearby. Ask for Linda Barnhart http://www.kentgamebore.com/?p=184

Another brand that is good for (easy on) English doubles is RST. They have a variety of shells suitable for your Evans, including paper hull 20 ga shells. They will ship direct to your door. http://www.rstshells.com/
Be carful with the American stuff, we use SAAMI specs when loading and the pressure is most often too much for a vintage firearm.

Then there is reloading. You will want to focus on loads in the 8,500 PSI max range. Sorry I can not be more specific.

BTW, what length are you chambers?

I think you will have better luck with Roger Lake than by going to Wm. Evans directly. I went to them and got a photo copy of the ledger entry for my gun. There was very little information in the entry and it took months to get, but was free. Roger's contact info can be found here: http://www.tavee.us/ParadoxHorsleySite/ParadoxHorsley.html
Just be prepared to supply those fantastic photos for inclusion in Volume II, he will want them.

I'd throw out the Armbrust (Marty Sands) loads. Look at this, crossing and low means velocity is too high - http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=158706&page=all

I am WRF in that story...