Autocockers use several different lengths of cocking rods depending on the back block style.
Here are the Styles and Lengths
•Classic Full Block, which usually used a 5 inch total cocking rod length. These are found on Sniper 1s, sniper2s and early autocockers.
Slanted block: these use rod with a length a little under 4 inches, typically 3.75 or 3.875 inches (total length).
P-Block: I am not sure of the actual length for a p block but depend on the style it could be the same length as a slanted rod / 2k rod or it could be a little shorter.
2k (usually the same as slanted block), typically uses a cocking rod length of a little under 4 inches, typically 3.75 or 3.875 inches (total length).
The Autococker cocking rod nut is typically 5.8th inches in length and the bumper is about a 1/16 or 1/8 inch? Not totally sure on the bumper size.