OH no wonder this blew up!! Yeah, we need to get it to play friendly with the rest of your rules
First of all, I don't see any rewrite here sending non-www traffic to www. I just checked, and I can go to the non-www version of your site, which could cause all sorts of cookie problems.
Could you try uncommenting this line and putting it up top, right below Rewrite Engine On
Code:
RewriteCond %{HTTP_HOST} !^www.gunsgrubandgold.com$ [NC]
RewriteRule ^(.*)$ https://www.gunsgrubandgold.com/$1 [R=301,L]
The www redirect really should be your first rule. If that works, then we can integrate the HTTPS rule too. Let me know