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IME, the only advantages of a .50 over a .45 are that commercial .50cal ML boolits are more widely available than .45's; and most commercial frontstuffers made today are .50's (which means that a .45 my not be available in a particular gun desired).
While I'd use a .54 on much larger game than I have available locally (New England), I long ago found that a .45 can take game here just as handily as the various .50's I've used in past years.
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