I went back to Lee spring and added to the tolerance and found some that should work , even if I need to shave a couple thousands off the retaining cap or retaining stem on the valve I'm able to do that but hoping I won't need to. Awhile back I splurged and got hammer springs from compression springs. Com, with the $40 minimum I have spares for everything and I found the perfect heavy hammer spring for my aea .25 challenger that nobody sells, it is shooting. 251 33gr slugs like a lazer and I think I'm going to up it to 40gr. Lee spring prices are very reasonable unless they have a minimum I havnt seen yet but I'll have a few in the cart. I'm trying to duplicate the hillairgun.com matched parts kit for the marauder. It's basically heavy hammer and valve spring with bigger transfer port and omg, my 177 marauder with lother barrel is shooting 20gr slugs so awesome it's just incredible and no regulator needed, it's so consistent . It actually shoots anything I put in very well, 178, 177, 10gr 16gr 20gr, pellets slugs