That's because they are using an aftermarket conversion barrel for that purpose alone. I don't know Glocks that well, but I'm pretty sure he didn't just drop any barrel into the glock22. Most likely he used a Lone Wolf conversion or another aftermarket, not one made by Glock.
There are no aftermarket conversion barrels for the sig 320/250 series. I can't see there being a large market for it, since the conversion kits are so readily available.
Even if you were able to find a used 9mm p320 barrel on eBay, the other things you will have to consider:
Can 0.40 extractor grab the 9mm rim?
Is the breechface is seated properly against the round?
Finding the correct recoil spring (and maybe even rod)
The barrel lockup on the p320/p250 series is very tight. It is probably why it is so accurate. I wouldn't play legos with the parts unless you know for sure it will fire without going kaboom.
There are no aftermarket conversion barrels for the sig 320/250 series. I can't see there being a large market for it, since the conversion kits are so readily available.
Even if you were able to find a used 9mm p320 barrel on eBay, the other things you will have to consider:
Can 0.40 extractor grab the 9mm rim?
Is the breechface is seated properly against the round?
Finding the correct recoil spring (and maybe even rod)
The barrel lockup on the p320/p250 series is very tight. It is probably why it is so accurate. I wouldn't play legos with the parts unless you know for sure it will fire without going kaboom.

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