I don't really know any born again christians in fact all christians are born again when they first believe. What denomination are these born agains?
Even in Aminianisn there is the belief in 'perserverance of the saints ' where a christian may be out of fellowship with Christ through sin but is still saved. In the Arminian tradition a christian can only be lost by the rejection of the saviour.
Calvinism on the other hand is the belief in TULIP. which includes Unconditional Election the belief we are selected by God through no reason of our own. This belief also stated there is limited atonement only for the saints and also stated the perserverance of the saints which is once saved always saved.
Once saved allways saved is very common in the christian church