I used to shoot a 40-65 browning and goex cart. Seems like my accurate load was around 60 gains, compressed roughly 1/16th inch .060 veggie fiber, dgl lube and a 400 grain brooks bullet. The wind is sorta tough on 40 cals at least m ore than it was on my 45. So maybe your load though light is suffering from lack of compression, bullet too far from riflings, again due to lack of powder, and of course our old friend the wind, lack of follow thru, ect ect. I would sure up my powder charge 60- 62 grains, compress powder roughly 1/16th, and make the bullet stick out far eneogh, but against the powder, to engrave the riflings lightly when closed into battery. With a roller you don't have much camming action so you need to be sparing on the engrave, but it should be there. Target test many rounds, dont let one or two groups make a call for you, blind hogs find acorns but the load you settle on should not be a blind hog. The bullet quality also comes into question. Develope a rythm to casting inspect and cull all suspect bullets. Watching for poor fill out, base tear out, and weight consistency. My first two years in bpcr silhouette were miserable due to a poorly made lyman mould. A custom paul jones took me from a class to aaa in one season. Long rambling post but you get the idea if you have read many articles. There is no magic bullet, what works for one guy may not for you, but there are general practices followed by most successful bpcr shooter. Last maybe its your gun, mines for sale, it will improve your results honest, just hacking at you, enjoy the sport. My world used to revolve around it.