You would need a bolt head for the small diameter firing pin.
The other way around.
Since his bolt head was built for a large pin, it is fine.
If he was putting a small pin bolt head on a large pin, he'd have to drill it out. I've done that to a couple bolt heads just to make sure they will work on all my bolt assemblies.
"Muzzle velocity is a depreciating asset, not unlike a new car, but BC, like diamonds, is forever."-German A. Salazar
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