I'm looking for an ER11 x 5/16" collet for the SAC 7PRC sizing die mandrel. It's the only thing holding up my order from them. It looks like it's probably a custom size and can't find one from the usual sources like McMaster-Carr and MSC industrial. The largest size offered for ER11 is 1/4". Of coarse it was supposed to be instock when I placed the order. Got the rifle together but can't size brass. Any help finding a source for this piece would be appreiated.