Did you know that a group of giraffes is called a tower? Many folks are likely much more familiar with a bunch of lions called a pride or a cluster of fish known as a school.
What one word would best capture the essence of who gun owners are, what we represent and what we believe? What term would we want to portray a number of gun owners together?
Sheepdog
Americans
Liberty
Free- would work too
Will have to give that some thought and get back to you.
According to liberals, a clip.
A “magazine” of gun owners?
An “ammo can” of owners?
A “holster” of owners?
How about an “armory” of gun owners?
Just off the top of my head…
Militia
Friends
THESE DAYS? A “TARGET”.
Blessing (group of Narwhals)
Parliament (Owls),
Patriots
FOP (Firearm-Owning People) 
FAG (Firearm-owning American Guys/Gals)
FLAP (Firearm/Freedom-Loving American Patriots)
SAFE (Second Amendment Freedom Enthusiasts) 
FLAG (Firearm/Freedom-Loving American Guys/Gals)
Street Soldiers
That was the first word that came to my mind as well.
A Posse - a group of people who have a common characteristic, occupation, or purpose:
A Brace, as in a Brace of pistols. (1.) Something that is used to support or connect things, or to make something stronger. ( Cambridge English Dictionary )
If we’re voting, I like the sound of “a magazine of gun owners”, it’s right up there with a “parliament of owls”.
Poor.
Posse gets my vote 
Lol, at first glance I read as Matilda. Back has me down and the meds are kicking in good right now.