The group also has opposed limiting the size of ammunition clips, something that is being proposed by President Obama, except armor-piercing or Teflon-coated bullets.
Some gun right advocates say that any proposed ban judges the weapon by its appearance rather than its capabilities.
"If you want to ban all semiautomatic firearms, you could talk about it," said David Kopel, research director at the Independence Institute in Denver. "But if you ban some semi-automatic weapons and not others then the ban is based on superficial accessories like a grip. That has nothing to do with public safety."
The administration's ban covers more than 100 specifically-named firearms as well as certain semi-automatic rifles, handguns and shotguns that can accept a detachable magazine, or rifles and handguns with a fixed magazine that can accept more than 10 rounds. Existing weapons are grandfathered, as well as 900 types of weapons used for hunting and sporting purposes.
Kopel says owners of the AR-15 and other semi-automatic rifles like it for sport shooting at a range, or to protect themselves from intruders.