Now that the half twist is put into the sling let’s adjust the sling’s loop tension. One of the things that will easily mark someone as a novice with a shooting sling is a lack of proper tension. This renders the sling ineffective. Why take the time to loop up if it’s not going to help?
If you get right down to it, every position will have an amount of sling tension that is appropriate for a specific shooter. That’s why competition folk use slings that adjust. They also have the luxury of shooting predictable courses of fire at known distances and a measure of time to setup their equipment.
If I really nitpick about it, I find that as my position gets higher (prone→sitting→squatting→kneeling) I require more sling tension. It gets pretty easy and quick to adjust if you do it a lot and your sling adjusts easily.
Sling tension is kind of a preference thing and varies a lot from shooter to shooter. Competition guys have a reputation for liking it very tight. I don’t think this is as practical in the field as a sling that is “snug”.
I think a good amount of tension requires that the rifle’s butt be pushed forward in order to get it into the shoulder pocket. I use the firing hand as I’m getting into position and push from the top of the butt. As I push it all the way forward it doesn’t become so tight that it simply won’t go forward any more, but it’s tight enough to push back on my shoulder after it’s been placed there.
A problem with adjustable slings is that they can un-adjust. I have experienced on multiple occasions a 1907 frog escaping from its holes, or a cam buckle on a USGI sling just coming undone. This can cause your rifle to fall (which is undesirable generally, unless your rifle is Russian).
Other slings do not easily adjust for tension. This type of sling is more suited to the user who does not expect to have the luxury of foresight to know what position he will shoot from or the time to make the adjustment. For this type of sling you can find one length of loop that is a compromise that will work across the spectrum of positions, perhaps not optimally, but it will work. I call this class of sling “set it and forget it”. These are generally simpler and more secure.
The way I adjust a “set it and forget it” sling is to set it slightly tight for the lowest position, which is prone. This setting should make for almost ideal tension in the sitting position. In rice paddy prone and kneeling, the tension will be less than optimal, but still very useful. I have considered setting the sling tight for sitting and just using the bipod in prone. That would give me better tension in rice paddy prone and kneeling, but I keep thinking I should leave the slung prone option open.
Incidentally, I have a friend who was able to shoot a 249 on an AQT using a fixed loop length (set it and forget it). Also incidentally, my sling design is also a set it and forget it. Hmmm…