I'm trying to install a Griffin taper mount so I can run my form 1 can, but the damn threads on my SAR are wayy too long. The mount is threaded all the way on, still has .110'' to go until it hit the shoulder of the barrel. I don't want to use a stack of peel washers, and I guess mine didn't come with the jam nut so what should I do?

Can you use the jam nut which bumps up against the supplied A-2 Flash Hider?

I got my Tavor second hand in a trade, it didn't have the jam nut, just an A2 with a crush washer.

IDK about any other manufacturer, but AAC says the gap is ok.

KBA Custom sells a spacer just for this issue.  It's pricey($29) but it allows proper alignment for suppressor mounts.  I used it on my X95 to mount a Rugged R3 Flash Hider.  I've had zero alignment issues using this spacer with my Rugged Surge.  

I've seen people just use the jam nut but I was concerned about alignment.  I had some Griffin and Gemtech shims but I didn't trust using them with the small shoulder on the X95.  I also didn't like the look of the nut and the spacer makes it look cleaner.  

http://www.capitolarmory.com/tavor-muzzle-shoulder-ring.html



Here are more threads about the Tavor's muzzle threads.  
https://www.ar15.com/forums/t_6_43/455314_-ARCHIVED-THREAD----Suppressor-muzzle-devices-on-a-Tavor-.html&page=1
http://www.ar15.com/forums/t_6_43/466631_tavor_muzzle_device.html

I tried spacers with my Specwar and couldn't get it right. I just ended up using my AAC with the game. Shoots just fine. Looks ugly. Guess I can darken up the threads a little.

well I went ahead and installed the flash hider/mount with nothing and left the gap, I then mounted the suppressor and checked with an alignment rod and it looks good. I pulled everything back off, cleaned the threads and rocksett the mount. as soon as it cures I'll do some test firing. I was also wondering if any of you guys that shoot suppressed a lot know which port cover is better, the MI or Manticore Arms?

There is a thread on the Bullpup forum which addresses the gas to the face issue.  Once you put the GH or MA port cover on the gas escapes out of the top at the rear of the Picatinney rail.  There is an X-Ray photo which shows why the gas escapes from this location due to the location of the bolt carrier.  Posters identified the leakage location by placing tape on the rail area.   Many people are sealing this area with a bead of colored silicone RTV which supposely really helps.  The gaskets on the ejection port cover helps but there is still significant gas escaping from the top.