Looks like a 6 to me.
Do you know the "sharpie" trick to help break it in? You cover the back bevel of the blade where the lock meets it with a sharpie or even graphite pencil will work. It works like a lube to help with "sticking".
I use a lead pencil for that. Gonna try the sharpie to see how that works though.
Looks like a 6 to me as well.