If its the group I am thinking about its a bit larger than GOA! Google them and check out the number of members, I think GOA is about 350,000+ members, NRA is 3-4 million + and the group that you are referring to is about 650,000. I may be wrong, check it out.
NRA is by far the largest and most influential of all the groups. But......they only have a tiny piece of all the gun owners that are out there. Maybe 75-80 million total!
Citizens Committee is closely associated with the Second Amendment Foundation out of Bellevue WA.
When your google it or check their websits you will find there is not much information regarding membership data!