"I" could tell you, but, the only one I know of is well can I say bunk?DO TRY the "bstaley"(SP) oring mod. Sounded to odd to me for a long time but was in a tinkering mood so on my 1720T (same adjustmets as a marauder) I gave it a try. Simply removed the hammer got 4 oring the correct size -113 for the pistol the marauder will need some larger number orings- did the recomended adjustments ( min hammer spring preload and stroke adjuster all the way out then aprox 2-3/4 IN-clockwise) first string showed a crazy 4 (four) fps extreme spread and a SD of 2fps. Best $100.00 I've spent one an airgun.I'm certain a search here will give you all the info.John