there are a number of "wildcat" variations based on a shortened 30-30 Win case.  I've seen several in 30-30x1.5 on the line at EG. There was one for sale at the Spring match in .30 Johnson. a complete outfit, CPA rifle, dies, cases, mould, breech-seater--everything except the 'scope as I remember, it was at a very reasonable price--would have made a good set up for someone who was wanting to get into the game.

one problem with them seems to be a perception (reality?--I don't know) that bottlenecked cases are a problem and that only straight-sided very gently tapered cased cartridges will work.  I have never understood that unless it is a matter of how powders burn in a tapered bottle-neck case--maybe its a matter of tradition and the powders we use.  many of the most successful unlimited benchrest cartridges are short fat bottleneck cases

Another is that with the short cases filled with modern fast-burning high-energy powder approaching the 100% loading density deemed optimum; tipping the case to insert it into the action, (assuming you are breechseating the bullet), pretty well requires an overpowder wad to avoid dumping part of the charge into the action.

Unless the case has a long straight neck and the powder level is up in the neck, properly seating an overpowder wad is a problem in bottlenecked cases.  using a floral foam or lube-sheet casemouth wad should solve that problem.

It might just be that since the consistently top shooters all seem to be using the short straight case-based cartridges it is assumed that the case itself is the key factor to winning.
 this is disregarding the fact that consistently winning requires a LOT of other components,  a good rifle and optics, Proper bullet selection, accurate loading process, good shooting techniques, the ability to recognize and adjust to range environment conditions, and the kind of luck engendered by LOTS of practice and experience.