You will have more problems than you might imagine. For one thing you have nothing for the rimless cartridge to headspace on. That means the extractor hook will have have to hang on to the rim while the gun fires, something that happens in many semi-autos with long chambers. It hurts accuracy. Altering a heat treated boltface is something to be cautious about. While not impossible, you really need someone who knows what they are doing in welding and heat treating as well as in shaping the thing. You will need a deeper shaped extractor to get into the .45 ACP extractor groove. Also, keep in mind the .45 ACP SAAMI pressure spec is higher (21,000 PSI) than the SAAMI standard .45 LC spec (14,000 ACP). Make sure your gun's mechanism won't be bothered by the 50% increase.
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