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Discussion Starter · #1 ·
Hey there everyone, I'm new here and I had a question for y'all.

I know with sigs for example the sp2022 you could change a 40cal to 9mm by swopping barrels only (some say recoil spring to and obviously the mags)

With a 40cal to 9mm you can do the swap because the breach face is big.. however if you try to do it from a 9mm to a 40 that will not fly.. that might be where a conversion barrel would come in..

Now I know you can use a conversion barrel and they sell them for the fnp and fnx.. however I can get a perfectly good oem 9mm barrel muuch cheaper..

So I was hoping if someone who knows alot about different calibers and breachfaces would be able to tell me..

I would think it would work.. as good as a conversion barrel.. or as good as using a 9mm slide with a 9mm barrel? Probably and obviously not I'd think it might expel more gas and maybe loose a little speed would it fire ? I'd guess so..

However I wanted to hear if someone every did it?

Orrr from someone who is like a genius who knows this stuff very well..

Thanks so much, I hope to hear from you soon.
 

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The FNS is not a platform that you'd want to insert an OEM 9mm barrel in place of the SW40 barrel, in an FNs40 upper. The outside diameter of the SW40 barrel, which is relative in size to the opening in the upper slide, is considerably larger diameter than the 9. There would be a lot of 'slop'.

The 40-9 conversion barrel accounts for the differences in tolerances/fitment, which translates to safer and more reliable function.
 

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Discussion Starter · #3 ·
The FNS is not a platform that you'd want to insert an OEM 9mm barrel in place of the SW40 barrel, in an FNs40 upper. The outside diameter of the SW40 barrel, which is relative in size to the opening in the upper slide, is considerably larger diameter than the 9. There would be a lot of 'slop'.

The 40-9 conversion barrel accounts for the differences in tolerances/fitment, which translates to safer and more reliable function.


I guess that would make sense if the barrels OD are that big of a difference.

You mentioned fns I'm assuming that's the same for the fnx though..

If it is so you know how much those barrels run new and who sells them? And another question is how much in comparison do they sell used for? How often do they cone up on the classifieds here?
 

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The FNS and FNX 40 use the same barrels, as do the the FNS and FNX 9 use the same 9mm barrels. The upper slide assemblies also interchange; however (regarding the FNX) the 9mm FNX lower will not accept the 40 magazine-- though the FNX 40 will accept the 9mm mag. So, I swapped the 9mm upper onto my 40 lower and used my FNS 9 mags for 100% reliability.
 

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Discussion Starter · #5 ·
Wait do you mean the fnx and fnp? The fns is striker fired and the fnx and fnp are hammer fired.

If you have a 40 and a 9 barrel can you possibly measure the outer diameter on each for me?

Thanks again.
 

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Discussion Starter · #7 ·
9mm is alot cheaper go shoot that's for sure.. As to if it's a better self defense round that's up for debate some people and some test say a good 9mm defense round is better then a 40.

I think they're both good and regular off the shelf defense rounds you'll probably find most of your mid level hollow points 40 might be better.

Anyway if someone has a 9 and 40 and can measure the outer diameter that would. E nice.

Thanks
 

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