I've just purchased my 1st pistol caliber AR, a circle 10 lower for glock magazines with an unknown upper with an approximate 10" 9mm barrel with an unknown keymod free float hand guard. The flash hider is a YMH, model ymh-80-52c I believe for 9mm. After researching and following the threads, I decided I needed a flash can.  I got one from a member here on EE.  It appears to be threaded on the inside rear portion.  When I slipped over the flash hider, it was obvious something is missing as it just rattled around.  

Besides mitigating the noise and flash for my wife and kids, my first suppressor will be on it at a later date.  I'm also using a Fab Defense grip that houses a Surefire poly light.  Right now, even with a cap over light, it sits directly below the flash hider.  I'd like to avoid damaging it from concussion and muzzle flash.

Your thoughts would be greatly appreciated.

I've been researching AR 9s for a while now, but haven't started my build yet. I haven't heard of a flash can that is used WITH a flash hider. My understanding was that a flash can was an alternative to a flash hider.

Can you post a link to the EE thread you bought the flash can from?

I like the look for Griffin's Blast Shield and it seems tailor maid for a three pronged FS. Also fits A2 FS.

Griffin Blast Shield

To OP, why would you need it for 9 mm coming out of a longer than pistol barrel?

^^^ This. Theres not really much flash out of a 9mm sbr.. Maybe the equiv of 3 blackcat firecrackers or 2 thunderbombs.

Now if you had a pap pistol in 7.62 that's pretty holy crap in the dark.

Just to be clear, the Fab Defense device, not a traditional forward grip, more like a AFG, also holds my poly streamlight.  It has a cover over the lens but I'm concerned the concussion and flash will destroy the lens or housing. (Easy answer, take it off ...) I do practice as I use it.  Eventually it will take over as a HD. I have further research that the YMH has a spring assembly for their suppressors that also attach a flash can.  The can would also make it easier for my wife & kids to enjoy it.

You can try it but honestly don't think you'll get much out of it. There's just not enough concussive force to begin with.. The yhm device takes the blast and pushes it forward like a linear comp so as a tradeoff you'll get a slight recoil increase.

Also that fab defense light grip is definitely an NFA item, aka not legal ! Anything vertical like that or that you can get an enclosed hand or thumb around is no go.

I had that same concern as well, but then I figured out he was refering to this:

Yeah that potatato grip version will prob be thumbs up but the other version with the vfg grip plus finger grooves, no

KAK or Guntec flash cans work great with 9mm.