Well, I have a Standard contour 243 barrel and it shoot's great!
I have only shot 1 brand through it so far-Winchester Super-X 100gr PSP- And my largest group was 1 1/4" My smallest being just over 1/2".
Some here have reported problems with their 243s.
I believe a lot of this to be different factors, like forearm pressure and stye of forarm. Also lock up, all my barrels require a little force to close or snap them up, and fit very tight and snug while closing. Some just take a little attention to detail, to get shooting.
Though I don't dismiss all claims by anymeans. Do a search and you'll find plenty hits on the 243 Handi.
It's a great caliber, and many loads offered for it.
I am very happy with mine.
-Aaron