asssault rifle ban for those on terror watch list - at least

What congressional Dems might suggest is to create an 'assault weapons ban' for those on a terrorist watch list.
That is to say, if not a total gun ban for them as is politically improbable, at least ban those on a terrorist watch list from being able to buy assault rifles such as the sig mcx or the AR15. These both use a low weight 0.223 bullet or the similar nato round which are so light at ~60 grains they do not create much rifle recoil, which makes shooting more accurate as the rifle needs not be re-aimed as much after firing shots, as do bullets with heavier weight & larger calibers. Also known as 'rifle rise' due greater recoil.
These assault rifles using these low weight bullets are 'en vogue' for mass shootings due the same reasons soldiers like them - can carry more light weight bullets, light recoil, & higher accuracy & lethality. The lady shooter at san bernardino was reported as having an AR15, or a 0.223 rifle, & she weighed little over 100 lbs, making the AR15 ideal for her - tho whether she actually shot, dunno.
Obtaining a handgun or conventional rifle by a suspect terrorist would generally not be as effective in mass shootings as these assault rifles.
At least suspect terrorists wouldn't be able to get assault rifles, while still being able to exercise their (barf) 2nd Amendment rkba.

...........AR15/M16 ..... AK-47 (122 grain bullet) >>>> Free Recoil
momentum 40.4 ft-lbs .. 54.3 ft-lbs
(some rifles have 240+ grain bullets with much greater recoil than ar15)
https://en.wikipedia.org/wiki/Comparison_of_the_AK-47_and_M16

Also, the nra is fos when saying a ban on all those formerly on a terrorist watch list (as recent orlando shooter) might not be deterred by a ban on those currently on a terrorist watch list.
Some 'formerly's' indeed would be deterred by such a ban, as there would be a 'threat' of being identified as having once been on a terrorist watch list, and this in itself would inhibit many of those people from even desiring to try to purchase a gun, for either an irrational fear of being reported to cops & quickly arrested, or being exposed by the gun dealer to the community he lives in, iow paranoia.

As far as 'law abiding americans' being prohibited from buying a gun if they are accidentally on a terrorist watch list ban, the gun lobby makes the absurd conclusion that all of these people would even want to buy a gun. Most would likely not even want to buy a gun, unless they were truly terroristic of course.
Some unfairly on the list would already be gun owners, thus not being left gun-less.
Most all of the rest should not complain severely about being accidentally put on one since they could simply go to sheriff or authority & provide proof that they are legal beagles, and weighing the positive benefits from a terrorist watch list a true citizen should understand. True terrorists generally could not do this.