I took a chance, spent the money, and had a custom mold made for REAL bullets in 40 cal. Tried them out in my Seneca which has a Rayl rebored barrel in 40 cal with round groove rifling. Using 60 grains of FFFg, being a light weight rifle, it smacks me pretty well, leaving bruises on both my shoulder and cheek. LOP is a little short for me which also contributed. After a few shots adjusting the sights, I got a shot in where I wanted to be and then fired 2 more for group before I gave my body a break and went to pistol shooting. I am very pleased with the performance of these bullets.