I have a old Thompson Center Pennsylvania Hunter with 1-66 twist that is very accurate 1" @ 100yds, We have a friendly competition @ our local club for shooting 200yds. My question is this, Will this rifle perform @ 200 yds? Or am I asking that 185 grain ball to do an awful lot?
Every one else is useing Inlines (some pretty expensive) I have asked them to have a Sidelock division and limit it to only open sights. Still waiting for the answer.

Hello,
 
Are the open sights on your rifle fixed or adjustable?  We used to shoot a round ball match at our club which consisted of five shots at a steel ram target at 200 yards.  With good conditions it was possible to hit the ram with some regularity.  The fixed sights on our rifles required that you hold quite a bit over the target which made getting a good sight picture impossible.  
 
If your sights are adjustable you should be more able to hit a ram size target at 200 yards more easily.  The rifle will certainly not shoot as tight at 200 yards as 100 yards but it should to okay.
 
Good luck.
 
Colin

I seem to recall reading recently that back in the day there were 200 yardish competitions with round ball guns.  As posted previously, calm is good, wind would be the devil's doing.  Whyn't you give it a try and see what happens.  You might teach those boys a thing or two.  Only person that could be disappointed is them....

Aye, HL.com too.  I be a repeat offender. Or frequent offender as it suits.  Luck to ya!