I've been looking at buying a .357 Sig barrel for my currently .40S&W post ban P229, I found a new in package Sig Sport .357 barrel for it, its threaded for a suppresor according to the guy. Now question is will this make my gun illegal when installed.  Thanks for any help

There is no such thing as a "post-ban" pistol. The 229 was never regulated by the AW ban. To the best of my knowledge you can put a threaded bbl on all day long. You will just have to get a stamp to buy a can for it...

No, it won't be illegal.

However, it does look like you may not have the right kind of thread, and enough of them, for a suppressor.  More likely, it was threaded for a compensator.

thanks for the replies... the guy said due to new regulations these threaded barrels were no longer available, and they have 12 round pre-ban magazines for it so i figured since i just bought mine new it would be considered a "post-ban" even though we dont refer to handguns like that as we do AR's and wasn't sure if that would effect my ability to modify it... as for the thread on the barrel he said since its a real sig barrel its threaded for a genuine sigarms suppressor, i did some searching on the internet and generic p229 barrels said "threaded half an inch longer than sig barrel to accept a wider range of aftermarket suppressors"

He was lying like a Persian rug merchant.  SIG doesn't make suppressors.  And if you want a threaded barrel, all you have to do is call CCF, Bar-Sto or Jarvis and tell them length and thread pitch..it'll be on your doorstep in a week or two.  Also, .357 SIG wouldn't be all that hot to suppress.  The SIG Sport (just saw this in your 1st post) is a compensated pistol...those threads are too fine for a sound suppressor.

Roger that. The .357 Sig works on having a ton of velocity, meaning that it is usually faster than the speed of sound. If you can that cailber you will just end up slowing the bullet down and ending up with an overpriced 9mm gun that probably won't cycle right because it has a .357 sig recoil spring in it.