[BullpupBen]

Since .380, 9mm auto, and .357 sig all use the same 9mm bullets (correct me if I'm wrong) do they all use the same barrels, except for twist rates?

If they do, anyone know the standard twist rate for each of these calibers?

[makarovnik]

Inside diameter is close I think.

[LightningMan]

Well in the No. 11 Speer Manual it shows the twist rate for .380 with a Browning barrel at 1-16, a Beretta 92SB 9mm is 1-10, and .38 Colt Super Auto 1-16. Sorry it doesn't list .357 Sig as the books older than the cartridge. LM

[BullpupBen]

So other than the twist rate they are essentially the excact same?

So if you put a barrel for a 9mm round in a .357 sig barrel it would work just fine except decreased accuracy right?

[AK103K]

The bullet diameters are the same, they all use a different bullet weight and profile, for the most part.

Most guns will not allow you to swap the barrels. You can get aftermarket 9mm barrels for some of the 357SIG guns, but you cant put a 357SIG barrel in a 9mm, or a 9mm barrel in a 380.

[BullpupBen]

I thought Glock 17's can be converted to .357 Sig?

[FieroCDSP]

M&P 40 and 357 Sig are identical and only require a barrel swap. The bullet profile between a 9mm and a 380 is substantial. The 9mm is more pointed, the 380 more of a rounded. A 380 bullet could probably load okay in a 9mm, but I'd be worrying about OAL and clearance in a 380 mag with a 9mm bullet.

The largest issue with loading them (I've looked into it, as I load for both) is the amount of case volume you are displacing. A 9mm bullet will take up a lot more volume in a 380 case, and spike the pressures higher because of this.

[mr.trooper]

So if you put a barrel for a 9mm round in a .357 sig barrel it would work just fine except decreased accuracy right?

NO. Not even close. While the Land/grove diameter may be the same, the barrels CHAMBER is completely different.

the only one of these you could get away with is a 380 in a 9mm, but its going be very inaccurate and it wont cycle the action. Shooting any of the other possible combinations is begging for a kaboom.

[FieroCDSP]

Oh, yeah... forgot to add that the 357 Sig is a bottle-neck cartridge. Think of a 10mm necked down and trimmed a bit to take a 9mm slug.

[AK103K]

I thought Glock 17's can be converted to .357 Sig?
If they upgraded the 9mm Glocks frames to that of the .40's, then yes, they probably can. I know Glock was having issues with frame failures when they tried to use the .40 in the 9mm frames. If the frames are still different between the different models, then I'd say no, you cant just swap the barrels.

Most of the other makers that allow barrel swaps, are between the .40's and .357SIG's, which are usually just a barrel swap. Some will accept 9mm barrels, but I think most of them are aftermarket barrels and not factory. The larger calibers can go down, the 9mm cant go up. Other than maybe Glock, or ther new SIG P250, I dont know of any of the 9mm framed guns being able to be chambered in the larger calibers.

[Jim Watson]

Bore and groove diameters are the same or so close as to not matter.
Rifling twist is all over the place and not a major consideration in pistol callibers.

Of course the chambers are completely different and the external barrel profiles are different, gun to gun. A 9mm conversion barrel for a Glock 22 is not the same as a Glock 17 barrel.

So the barrels and ammunition are not interchangeable, but you could make a barrel for any of those calibers out of the same rifled blank and it would work ok.

[BullpupBen]

Bore and groove diameters are the same or so close as to not matter.
Rifling twist is all over the place and not a major consideration in pistol callibers.

Of course the chambers are completely different and the external barrel profiles are different, gun to gun. A 9mm conversion barrel for a Glock 22 is not the same as a Glock 17 barrel.

So the barrels and ammunition are not interchangeable, but you could make a barrel for any of those calibers out of the same rifled blank and it would work ok.

OK thank you that is exactly what I was asking.

[19-3Ben]

Another point, but I'm not sure I'm correct. But usually (Kel-tec and Ruger LCP being notable exceptions) .380acp are blowback operated whereas 9mm and .357sig are not (hi-point being an exception to that rule).
So in a blowback the barrel is fixed to the frame, and in recoil operation the barrel is not fixed. So it's a different design on the outside of the barrel anyway. And good luck finding a .380 conversion to a 9mm that would function reliably with the lower powered .380's.

Just a thought, and I could be dead wrong.