Absolutely right, you can scroll only by pressing Num1 key (in default settings) among SinglePlayer Weapon and as advice don't get carried away when scrolling through SPweapons for a long time, approximately after Anti-Air Mine the game may freeze. Also pay attention to some unknown slots in SPWeapons (with no pictures) they could contain very interesting sort of weapons.
I hope you will have unlimited fun with it
Detailed visual information about it I've posted in Tutorials