9mm or .40 s&w
 

Seems like every gun I've been interested in lately has a 9 and 40 version. Never shot a 40 so I don't know the pros and cons. I was turned off at first by the fact that the ammo is quite a bit more than 9. Is it worth it to take the gamble on a 40, or stick with the faithful 9 for my next purchase?

Up to you, I always go with cost and popularity of ammo. 9mm, 45acp, and 22lr. I will do nothing else ever again.

If you bought a s&w mp40, you could get a 9mm barrel for it and s couple of 9mm mags and have both. BUT you can't put a 40cal barrel in the 9mm pistol. Only the 40 pistol

But is that going to affect the accuracy and reliability of the weapon?

Many buy switch barrels for their pistols but I have to wonder how often they switch? I would guess they put one barrel on and use it exclusively. So what's the point of having two barrels? The 9mm has more mag capacity, cheaper more readily available ammo, less recoil

Not to my kmowledge. Have seen it done and used with Glocks. Also believe the Firestars M40 & 43 are interchangeable. Haven't bothered trying because I'm more than happy with 9mm due to ammo convenience (as mentioned already).

I work in sporting goods at Walmart and we always seem to run out of 9 and always have 40 so I don't see much in the way of convenience on that one

I've yet to have that problem at the places I shop, but could understand the position at Walmart. I hear all the time that they have great ammo deals.

We mostly do. I've figured out that I can get a better deal per round on mostly anything made by federal with my discount than any other bulk price I've found

You can also get conversion barrels for the xd/xdm. I just got a xdm40 and plan on living up the conversion barrel for it. Ill probably run 9mm at the range and keep 40s in it the rest of the time. I have been wondering how long it'll take to pay for the barrel with the money I save on ammo