Shouldn’t fire slugs in anything tighter than a Modified Choke. And I believe the Fox model B’s were. Though I’m not certain of the choke off hand. However, easy enough to search what Choke they use. Someone here likely knows.
EDIT:
Well now, I just found this I posted below which indicates the Right barrel is Modified Choke & Left Barrel is Full Choke for all except .410. So if this is correct, than a slug in the Right Barrel is fine.
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