i am having problems sighting in my rossi .243. I have been through 3 scopes and a set of rings. i can shoot it and get a group of 3 within 5inches at 100 yds, then bam no groups aftr that then ill get a group agian and again it starts shooting off the paper. with this being a cheaper made rifle could this be barrel heat up? or could something else be the problem?i just readon another forum that the bolt that goes from through the stock into the bottom of the barrel can affect accuracy, is there any truth to this?