I recently purchased my first can, an omega, which will be used on a tavor.  For now it waits in jail.

I know I need to remove the flash hider off my barrel and put their mount on it.  I've seen some discussions here about having your barrel rethreaded to make sure the threads are correct.  Is that something I should have done to mine, or is it ok from the factory?

I also have a tavor that I will be using with my omega (also in jail). The threads should be ok, just check alignment once every is together. And Do not reuse the jam nut that is on there now

The threads should be fine, just check alignment once mounted.
One thing you will probably notice is that the muzzle device will thread on and bottom out before threading all the way back. This is because the threaded part is extra long. Some people have been sending their Tavor barrels to be cut, and then perm attach an omega flash hider so that the overall length is still 17" but it looks better and reduces overall length.

If you have the mount it came with just thread it on and you will see what I am talking about. It should work fine, but will look kind of goofy (IMO).
Also it will be a pain to shim. If it were me I'd cut the barrel and perm attach a mount so it was perfectly flush.

Is there an alternative, say a spacer or something?

 

Another retarded question: how should I go about permanently attaching their mount?

Got it, don't reuse the nut.  Why, out of curiosity?

 

It can cause alignment issues.

I haven't mounted a muzzle device yet but will probably try something like this. http://www.brownells.com/rifle-parts/barrel-parts/rifle-barrel-hardware/washers/ar-15-m16-ar-style-308-accu-washer-muzzle-device-alignment-system-prod54363.aspx?avad=avant&aid=41227&cm_mmc=affiliate-_-Itwine-_-Avantlink-_-Custom+Link

Which one, 5/8 x 24?

The tavor will be 1/2x28.

And use some rocksett

Ok great, thank you so much.

 

Let me know if those work out. Hopefully there is enough shoulder.