too close and should extend my butt pad to have less bend in my elbow
The proper length of pull is all about being able to efficiently run the rifle (not the optic) correctly in a relaxed un-muscle-ed manor.
So we have all seen the crook of the elbow to the trigger finger measurement. This is a good starting point. Now we need to get into the prone shooting position (without the scope on the rifle) and start to dry fire. We are looking at 3 things to refine the length of pull.
1. Placement of the cheek on the cheek riser. We need to make sure we are getting to a comfortable place on the riser. Making sure our face is not hanging off the front or the back is all we are looking for here.
2. Crook/kink in the firing hand wrist. If the wrist is kinked to much we start to loose dexterity in our fingers, especially our trigger finger. Rolling you thumb to the hand side (rather than wrapping it around the stock or grip) can help this dexterity too. We are looking for easy movement of the fingers and a relaxed, un-muscled wrist position. If our wrist starts to hurt after a few minutes because we are having to wrench it back to get a good grip means our LOP is too short and may need extended.
3. Running the bolt. Running the bolt is, for me, is the true test of length of pull. We want to be able to run the bolt without fully lifting our elbow off the ground. Some elbow movement is okay but having to lift our elbow to eye level to get enough leverage on the bolt lift means our LOP is too long and needs shortened.
Finding the sweet spot in these 3 is the key to length of pull.
Once 1,2 and 3 are comfortable; now mount your scope and set the eye relief to match
your position Do not make your body get to the scope, bring the scope to you.
or if my head is too canted and i should lower the cheek rest
Head cant and cheek rest height have very little in common. (some but little)
Cheek rest height has 2 factors. 1. The height of the scope over bore and 2. what type of cheek weld you y have/want (chin, mid cheek, cheek bone) Cheek rest height is all about getting proper eye alignment behind the scope to have proper sight picture.
Head cant comes from the height of the rifle system from the ground and your body type. In general, the lower you put your rifle to the ground the more your head will role over. The higher you put the rifle will move you head more vertical. I have a bigger frame and bigger body type (starting my diet "next week") so I prefer a higher rifle position. This puts my head in a near vertical position and my body is supported up on my elbows. I have a tall bipod position and tall-ish rear bag to get to this position. If your rifle is too low your head position and neck tension will surly tell you in a hurry. Listen to your neck the most, if its hurting after being in the prone position for 15-20 minutes, you are too low.
Now, all these items have to come together. (LOP 1-2-3, Cheek height, rifle Height) Changing our rifle height from the ground can change how we can run the bolt because our body and body support is in a different position. This can also change our cheek weld position front to back. Changing our cheek weld
type can effect your rifle height and cheek riser height. This will take some time to iron out as you start shooting more and more. Make minor tweaks and adjustments as you go. Once you think your are comfortable with your setup change something slightly like adding or shortening LOP just a bit and see if you like it better. Raise and lower the bipod height to get a feel for what is most comfortable for you.
Ready, set, go. Good Luck.