Re: 243 Win.
All I ever shoot out of mine is 100 grain serria game kings that I load. I use it for everything so I don't have to change the scope settings.
My pump gun has a fast twist, and it doesn't seem to shoot light bullets all that well, but those 100 grainers shoot awesome.
In all reality if you don't reload I would get a couple boxes of cheap 90-100 grain loads, and try them. I would start with the Remington green box for a number of reasons.
Venison - The other fast food