SR9 Silencer?

[desertrat]

.....How thin can you cut down the end of the barrel for threads before it is too thin?

My take on it is that barrel wall thickness, in many cases, is more than necessary to handle cartridge pressures. On semi-autos like the SR9 it may be that the wall thickness is what it is, more for balance & recoil functioning than it is for pressure. Take a look at some of the .380 mouse guns & notice how thin the barrel wall is on them. Another example is the classic Colt 1911 .45 auto. Barrel isn't all that thick there either. Granted the .380 doesn't produce the pressures that a 9mm does but it approaches it.