How a boolit trap can help solve leading issues

for about two years now I've been trying to solve the leading issue in my 9mm. I have tried all the normal things, slugging the barrel, adjusting one variable at a time, keeping good records, sizing the bullet etc. My calipers are apparently not accurate enough to help solve this problem the way they should. According to them the bullets should fill the bore, But they don't.

Through lots of reading on this forum and help from members here I have to deduced that the bullets are too small. All the symptoms seems to indicate is much. I ordered a larger mold and have today tried shooting them in my 9mm. they are sized at .358. I also recently built a small and portable bullet trap. Below are some examples of what I collected. I found it very interesting.

The top three bullets are not from my 9mm. They are from my 357/38 however they're the same type of bullet as the middle row only larger. You'll notice the lube grooves have retained there definition and the rifling is cut in the bullet. The bottom row is the new bullet shot for my 9mm sized to .358. Again they have retained their definition and engraved a good rifling. The middle row is the old bullet the lube grooves are practically gone and there is just the faint shadowing of a rifling. As I see it the bullet is traveling down the bore probably not taking on much of a spin. The lands are essentially just barely engraving. The result is the lands, which are in a spiral, shave the boolit down as it travels down the bore at a spin slower than the rifling.

It is a working theory but it doesn't look like gas cutting to me, at least not entirely. Where is all the lead that used to be lube grooves? In the barrel of course and blown out the front of it down range. The result is horrible accuracy bad leading and lots of frustration. Having a bullet trap makes identifying this quick and easy because you can compare your results with other loads you know work.

The result is a theory drawn from evidence and the advice of experienced folks. The theory applied and results can now be observed and the theory confirmed. I found a pretty interesting. Thanks to all of you who have addressed the leading issues on this forum.

P.S. the black gunk is from the rubber in the trap if you are wondering.

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