With the shape of the .40 bullet, I would suspect that a soft bullet like those may have more drag, than a pointy bullet like in 9mm. The .40 is a little more finicky when loading from slide lock.
IMHO you don't save any money and get and inferior bullet with moly or black bullets. Also Berry's bullets are garbage, I wouldn't run them ever again. They are the softest plated bullet by far and are probably why plated bullets get a bad rap. Rainier are a little harder and are excellent, then Xtremes are even harder (and my personal preference). If you buy bulk from Xtreme you can get the cost down. .40 RNFP are like $87/k delivered when you buy in bulk.
I wouldn't go any heavier of a spring than a 9lb on a .40 minor gun, or you start to lose that nice "flat shooting" feel of the Tanfoglios.
Oh and like others have said, on a straight case round like the .40, having enough crimp is very critical to good feeding.
I tend to disagree with your assessment. The lead that BBI uses is certified 92/6/2 lead with a BHN of 18. This is actually harder than the plated manufacturers use. Lead will always be more accurate than plated....always.WJM - give me a call and we can help you thru some of your issues