I think a Bowie "should" look like this:
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But I've seen lots of fantastic Bowie knives with notable variations. Tony Mont, Nick Wheeler, Ben Seward, Jerry Fisk, and Bill Bagwell come to mind for makers known for their Bowie knives, although there are many others doing great work. I'd be tickled pink to own a knife from any of them.
The W49 is also pretty hard to beat.
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I was surprised to find how relatively thin the bladestock is on the W49. You'd think a Bowie that big would be chunky, but it's quite the opposite. It's still tough and the broad blade chops and slices very well.
I also really like Cold Steel's Bowies. The Recon Scout is handy, but the Trail Master is my most used Bowie to date. I tend to gravitate to larger Bowies: if I'm going to carry a Bowie I'd might as well make it count.
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As for steel types, something tough that holds a good edge for a long time. I've been happy with O1, 52100, Carbon V (1070B, I think?), and 3V so far so something of that ilk would work. I'll bet AEB-L would do great.
A classic coffin handle and sharpened swedge is a winning combination.
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