I have an old Weaver J4 on my 250 and really like it. They are 3/4" tube but some have a 7/8 objective. (belled at the front). For being so old I was very impressed with how bright and crisp the view is compared to a typical 3/4 scope.
There is another one here I just got with the fine cross hair, it will be nice for target work. The one currently on the 250 has a post crosswire which is great for hunting but not so much for shooting groups. Not sure if there were any double crosshairs available in this scope or not.