This JP Enterprises Gen 2 Silent Captured Spring System is designed for 9mm applications. I would recommend model: JPSCS2-15H2, which can be found by using the link below:
https://www.opticsplanet.com/jp-enterprises-gen-2-silent-captured-buffer-spring-system.html
This JP Enterprises Gen 2 Silent Captured Spring System is optimized for 9mm PCC rifles. For .458 SOCOM. I would recommend the JP Enterprises Gen 2 Silent Captured Buffer Spring System (H2) found by using the link below:
https://www.opticsplanet.com/jp-enterprises-gen-2-silent-captured-buffer-spring-system.html?_iv_gun-model=ar-15&_iv_additional-features=heavy-h2-buffer-version
The JP Enterprises Gen 2 Silent Captured Spring System could be used with a PCC chambered in 45ACP.
Yes, the last round bolt hold open should work fine with the JP Enterprises Gen 2 Silent Captured Spring System.
This is the gen 2 H2 version.
This is specifically for the AR9. This AR9 H2 SCS System weighs in much heavier (11.2 oz.) than the AR15 H2 setup (6.9 oz).
This weighs 11.2 oz.