That's good that it is a 2 1/2" chamber job. Just avoid U.S. 2 1/2" fodder as that is a bit too much as regards pressure. Certainly Eley, Lyalvale and Fiocchi all make suitable stuff. British standard 2" load is 5/16th. ounce of shot and the 2 1/2" load is 7/16th. ounce. Lyalvale do load there's with a full 1/2 ounce and looking at a box of Fiocchi I have they load 3/8th. ounce. Lagopus.....