hello,,if your barrel wasn't crowned properly after it was cut it could be the reason for your accuracy issues ,,a good gunsmith could recrown it and it may be cheaper than replaceing the barrel,,i've also seen recrowning tools available threw Brownells for the do it yourselfers'd look that route before changing the barrel,,but if you still feel a barrel change is nessasary heres some sites to look at,,gunparts i checked
ihttp://www.e-gunparts.com/DisplayAd.asp?
chrProductSKU=593750A&chrSuperSKU=593750&MC= heres a link to what they have in barrels for the 340 but it says there outa the 222 barrel but they do have a 223 in stock pretty cheap,,might be something to think about with all the surplus 223 out there ..might be cheaper to shoot than a 222 these days and should involve minimal gunsmithing in the changeover,, i'm pretty sure the mag will work from the 222 but thats something you'd have to check for sure with a gunsmith or try a 223 case in your mag to see if it fits ok,, if memory servers me right the cases are dimensionaly the same,,be a nice options if ya can't find a good 222 barrel,,a couple other sites might be bobs gunparts
http://www.gun-parts.com/index.html/ or popperts gun parts
http://www.poppertsgunparts.com/ try those i think one should be able to help ya ,,
bigcurt