Here is a series of groups that I shot from 25 yards. The ONLY thing that changed from one group to the next is where the sling was mounted to the rifle (I.e. sling tension)
After each group I moved the sling one rail closer to the hand guard and shot another group. Where the sling is mounted in the below picture was the position of the final group.
(http://farm9.staticflickr.com/8478/8186227595_046ab02f8a.jpg) (http://www.flickr.com/photos/25739591@N03/8186227595/)
Rail (http://www.flickr.com/photos/25739591@N03/8186227595/) by nlcarlisle005 (http://www.flickr.com/people/25739591@N03/), on Flickr
Group 1: sling closest to the muzzle
(http://farm9.staticflickr.com/8338/8186217161_3264ba9251.jpg) (http://www.flickr.com/photos/25739591@N03/8186217161/)
Group 1 (http://www.flickr.com/photos/25739591@N03/8186217161/) by nlcarlisle005 (http://www.flickr.com/people/25739591@N03/), on Flickr
(http://farm9.staticflickr.com/8340/8186218497_126a3964a0.jpg) (http://www.flickr.com/photos/25739591@N03/8186218497/)
Group 2 (http://www.flickr.com/photos/25739591@N03/8186218497/) by nlcarlisle005 (http://www.flickr.com/people/25739591@N03/), on Flickr
(http://farm9.staticflickr.com/8490/8186220429_65e1a4f67b.jpg) (http://www.flickr.com/photos/25739591@N03/8186220429/)
Group 3 (http://www.flickr.com/photos/25739591@N03/8186220429/) by nlcarlisle005 (http://www.flickr.com/people/25739591@N03/), on Flickr
Group 4: sling closest to the hand guard
(http://farm9.staticflickr.com/8349/8187264504_72ce2cf262.jpg) (http://www.flickr.com/photos/25739591@N03/8187264504/)
Group 4 (http://www.flickr.com/photos/25739591@N03/8187264504/) by nlcarlisle005 (http://www.flickr.com/people/25739591@N03/), on Flickr
I am now officially a stickler for sling tension/support arm position and you should be too!
Sling tension and the extension of your arm are not directly correlated variables. You can have your arm in a tight v (hand closer to the magazine) or extended straight (hand closer to the muzzle) and you can adjust the sling to be tight or loose in any of these variants. Granted, as the arm gets really straight it becomes harder to get maintainable sling tension so there is some relationship at the extremes but sling tension and arm shape/hand position should be treated separately.
Most people once they discover "sling tension" tend to overdo it for a while (the "banjo stringers") but eventually you learn the happy medium (who should always be struck forcibly :-).
Laying too flat on the rifle (arms extened, shooter geometry too straight on to the target) at one extreme versus propped up on the elbows too high too angled to the target are the other variables which interplay here. All should be experimented with until you find that position in which it is almost impossible not to have natural point of aim.
Enjoy.
Cheers
V
very good point! I did have a tight sling in each string of fire, so I suppose the real variable I was experimenting with was the amount of support arm extension.
Quote from: triggernick on November 15, 2012, 12:05:18 PM
very good point! I did have a tight sling in each string of fire, so I suppose the real variable I was experimenting with was the amount of support arm extension.
That answers my question. I was going to ask if you locked the keeper and used the front swivel change to relax sling tension, or it you used the swivel location as a hand stop and adjusted the sling to a consistent tension.
If the first, then you got improved groups as the sling tension relaxed. Too much tension can cause your NPOA to be difficult if impossible to find because your body is never able to relax.
If the second, then you got improved groups as you built a more sturdy triangle. Ideally you would want as close to 60 degrees on each angle of the support platform. Forearm, upper arm, rifle. Each body and each rifle being different, that may not be possible, and may not be ideal, but I would think somewhere around that shape is best. I know when I watch students shoot, those who shoot Rifleman and display good NPOA, almost always have a balanced and equal triangle formed with the rifle and their forearm/upper arm.
YHJ
Good stuff and I've discovered for myself that sweet spot combined with the sling swivel about 2" forward of that gives me the most solid position, not that I can't shoot well with other geometries, just not as well.
On our loaner rifles I put multiple sling studs and watch a student to see where their hand is to get the right geometry as YHJ suggests, then move the swivels. Be sure to explain what you are doing to the students, point being, make "your" rifle fit "you" otherwise they won't make the connection and will draw the wrong conclusions....O.L.
I believe this discussion thread by distinguished instructors confirms my observations. First, I believe many students have their sling much too tight and this interferes with being relaxed as YHJ notes above. In essence, they are fighting their sling. Second, I generally prefer to see a smaller angle on the support elbow with the support hand closer to the magwell/trigger guard as opposed to being further up the stock. These are "general" rules and can obviously vary with the shooter. Great thread!
A really good drill to expirament with sling tension is to sling up and shoot a group. Then take one inch out of the sling and shoot a group. Then let two inches out (so you have shot a group an inch tighter and an inch looser) than your original position. Do so with iron sights without going downrange. this will show you how sling tension changes you in a really interesting way. I encourage new instructors to do this so they can learn sling dynamics.
I have found that the best relationship of sling to arm position is to have anywhere from about 100 degrees to 120 degrees of upper arm/forearm angle across the elbow.
I have found that the sling needs to have enough tension so that I can relax the support arm completely and still have the sling hold the rifle vertically in line with the target (within limits of NPOA adjustment), and act to pull the rifle butt into my shoulder (it won't fall away when I relax).
Of great importance, I have found I get the most sling support when my support hand can be up against the sling swivel with the sling strap snug against the back of that hand. Shooters with short arms/far-forward sling swivels merely have the sling pass along the side of their support wrist without it contacting underneath the support hand. I believe that offers very little 'hold-up-the-rifle' support.