I am using a stock .40 STI Trojan with Tripp Cobra 10 round system mags. I am using the same load as for my limited gun(stock edge). Length 1.178, win spp, 4.6 gr of tite group with 180 gr blue bullets, mixed range brass. So far I have had no issues, except trying to load the stock sti mag(too long). The gun runs fine. Maybe try a different bullet profile? The reason I went with the Trojan in .40 was so I could use the same load in both guns with the added bonus of single stack or lim 10. I guess I got lucky with the choice.