It lists the 100grain Sierra ProHunter at 0.970" long. As a comparison, the Speer 87grain that works well in the 1:14 is listed at 0.82". If I recall correctly, you posted that you have a .250 that was re-barreled from a 22HP. If it was rebarreled at 1:10, the Sierra will most likely work; if 1:14, doubtful.