A slightly loose hinge pin would not cause a previously accurate Encore to suddenly shoot 5-6" groups at one hundred yards. Neither would loose thimbles: The thimbles on my Encore have been loose since i bought the gun, it has not caused any problems with accuracy.

There is something wrong with your scope, scope mount or rings. It may be related to your trip to the gunshop.

I had terrible accuracy with my Encore, went the Bellum's route with a trigger job, 1x hinge pin on the .270 barrel and a 2x on the muzzleloader barrel and the heavier barrel locking lug spring. Made a world of difference for the better. Did the work myself only had to buy the parts.

Grinder67, I may have your answer. Actually not "my" answer, but that of writer Randy Wakeman in one of his muzzleloader forums.
The exact same thing happened to my Knight Wolverine that once shot 3" groups at 200yds (no I'm not kidding).
Mr. Wakeman suggested replacing the breech plug with a brand new one (same model of b. plug of course) and... cha-ching! My groups once again returned to their great original accuracy.
Turns out that breech plugs slowly erode away; progressively changing your barrel pressure ever so slightly.
Hope this works for you as it did for me. jimsmokepole

grinder67 problem solved with declining accuracy
 

Grinder, I just posted to your question about your loss of accuracy in your inline rifle.
I hope it went through, but not sure so I'm doing a general reply too.
Anywhoo, after I experienced the same problem, I found / read an article by writer Randy Wakeman who suggested replacing the breech plug. It worked perfectly for me. Hope it helps you too.
jimsmokepole

I hadn't thought of the breech plug, but that could be a possibility. My first guess is still the scope/mounts/rings. It seems to me that if your accuracy was good before, then the scope was changed, and now your accuracy is bad, then it's probably the thing that was changed. Maybe try pulling the scope and shooting open sights at 50 yards and see what kind of group you can get.
I would also maybe recommend dropping your powder charge, though if that's the load that been working I suspect it's suddenly going to change.
Those would be the two cheapest tests, so that's where I would start. If you're still having problems then I would look into hinge pin locking springs, etc.

By Jove, i think you are on to something.

wow .......................and all i had to do was change to BH209

The scope work came after I had noticed the accuracy problem. I had aluminum rings and one of the screws had all but pulled threw the ring ( probably from over tightning on my part) so i replaced them with steel. The breach plug idea is interesting i think I will replace it and see what happens!

I would change the breech plug I have 3 encores and 5 breech plugs carbon also builds up in them also.

Those of you replacing breech plug because the flash hole has noticeable eroded, keep in mind that you can refurbish the worn plug by installing a vent liner. Don't toss them worn plug. Sabotloader has posted at least one thread showing how to do the work. First time through for me, was kinda nerve wracking, but now a day i do this work before breakfast, and find it trivially easy.