I also have the katahdin 209x50. My encore had the 28 inch originally. I bought it because of multiple states late season inline only hunting. That 28" barrel had some weight carrying and being a fan of short barrels I saw the katahdin and bought it. Much easier to carry and stalk with.
Accuracy is very good. I've only shot BH209 out of it. I use lighter bullets. Tcshockwave 200gr. I can keep it less than 1inch groups at 100. Have shot some very nice bucks with it and never recovered a bullet. I started using Hornady XTP as well. 200 and 240 gr. They both hit almost same spot as the Shockwave with same grouping. My 28" barrel liked around 90 grain of BH209 with the shockwaves. The katahdin likes 85 and 105 grains. I use 85 now because of powder cost and not being able to find bh209. Id start at low grains maybe 80 and work your way up to 110. Maybe little higher. I believe blackhorn gives stats and how to work up loads on their website. The xtp are 44 cals and I use the green harvester sabot that fit them. Much cheaper to use the xtp. This is one of my favorite guns and it is very accurate. I hunt whitetail mainly. For your elk hunt you can use heavier xtp's or the Shockwave would prob be fine. Hornady has a newer bore drive eldx that you might want to check out also that is made for reaching out. I have a pack but didn't get chance to shoot them yet. Best of luck this season.