Rifle is an Armalite DEF10, 16" .308.
I would like to put a dual lok flash hider on it, ideally.  However, I've had an issue with it trying to put on the AAC 3-prong in the past; the one I tried at least did not have long enough threads to make it, and bottomed out on the front face of the barrel long before getting to the shoulder.

I'm measuring about ~.79" of threading between the front face of the barrel, and the 90 degree shoulder.

Will the "normal", or long (or any) Dual-loc muzzle devices fit on the end of this barrel?

Thanks

That's not going to work with much.  It would be a better candidate for a over the barrel 762 flash hider mount.  The Dual lok OTB flash hider mount would cover the unsightly gap.  

It's odd they used such a long thread.  That's highly unusual.  Our flash hiders can muzzle index.

Thanks... I just checked for real with a caliper and it is actually more like just a hair under .74".  Any chance that would make a difference?

You need a .100" flat washer shim to mount it ideally.  Otherwise you will have a gap.