My M17 slide has a chamber load indicator. I need to order a spring and the indicator from Sig. Meanwhile will a standard P320 5” barrel non-chamber work? Are there any barrel locking issues?

no idea on your specific question. But you can run the M17 slide without the LCI without issues. And as a personal experience I lost the LCI spring when first learning to change the optics plates and SIG would not sell it to me. so good luck.