Minute Man Machining
The best-built version of the open-source Twitch design: 4140 pre-hardened steel, caliber-specific, one week out.

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The Twitch started as an open-source forced reset design released by ToadLicker556 for the MPA Defender, and three vendors now sell versions of it. Minute Man Machining's is the best-executed: 4140 pre-hardened steel, cut in three sizes for MPA 9mm, 5.7, and .45 ACP hosts, and quoted at roughly a week from order. It is the only Twitch variant offered in a .45 size, and at $120 it is cheaper than FTA's $189.99 steel version of the same design.
Caliber-specific sizing matters here. The Twitch geometry interacts with the bolt, and MPA bolts differ across 9mm, 5.7, and .45. A vendor that cuts three sizes is engaging with that; one that sells a single part is asking your gun to accommodate it.
The important caveat is not Minute Man's build quality, it is the design's provenance. The original Twitch beta release warned that testing produced out-of-battery detonations, with heavy lubrication appearing to reduce the problem in limited testing. Minute Man's page does not repeat that warning, but it is the same design lineage. Function check carefully, lubricate generously, and have a gunsmith look at the gun before you shoot it.

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Add the Minute Man Machining The Twitch (MPA) to your build and see how it enhances your platform.