McAllister, 23 linked up with Shrewsbury Town on Friday on a months loan - he made his full debut at home to Gillingham in a 2-1 victory on Saturday. Formerly with St. Patrick's Athletic he has been a fringe player since signing twelve months ago.
McAllister and Tonne have signed deals to keep them at Bramall Lane until mid 2014 whilst Chapell and Adams have penned deals until the end of the season.