What about Short Range Centerfire Benchrest ,and then as a sub description include the calibers most often discussed, or "discussions on 100-300yd benchrest competition". We have the 600-1,000yd forum which is fairly specific, why not just narrow down the title. It may not be apples to apples, but on 6br.com, I don't look at the "sub-caliber" or "6mm and up" forums, or at the advanced gunsmithing forum because I don't have any rifles that fit that description, and I am not in any way, shape, or form a gunsmith. If I do look I certainly don't post.
It may not require a whole new forum, but a renaming of the old one. Let's face it, the centerfire benchrest forum is PPC, BR, and similar cartridges...those who shoot wildcats for extreme accuracy are not looking for advice about their sporter barreled 300win mag deer rifle. They know where they belong so to speak. If you include a small description in the title you will help direct the folks whose efforts would be better spent elsewhere.
Mike