Factory set up was two recoil springs on 4516, 4516-2 and -3 and 457. Only compact 45 S&W tried a single recoil spring on was the 4516-1 and that did not work out so well and they retro fitted the two spring set up if you started to have ejection problems. If you are using a single spring Wolff it would be a good idea to keep spares and change on a regular basis.