How can I know my rifle is short or long action?

Rapter300

Private
Minuteman
May 31, 2010
1
0
51
I just got Rem 700 SPS Varmint 26" barrel and would like to get a single piece scope base for it, But it have two option for short action and long action, so which one is the correct one that will fit to my rifle? By the way what diff between short and long action. I totally new on rifle.