Monday, September 24, 2012

Range Report: Slings

Walking around the local show awhile back, I came across a vendor demoing an optics configuration identical to mine:  a Sightmark holographic sight with a 5x magnifier.  Except the demo had none of the smearing that mine had; the reticle was in perfect focus.  That was all the motivation I needed to call Sightmark and gently insist that they repair either or both of the optics, as needed.

They did, and I was quite happy with the result:

DSCN1055

Now that’s the sight picture I wanted.

So, it was back to the range.  But I made another change in my technique.  I started using a sling, specifically using a “hasty sling” to help brace the rifle.  I also had some new ammunition to try out.

Lake City FMJ1F 55gr.:

Lake City 55gr with sling

This is the tightest group I’ve ever shot.  Unfortunately, I was unable to repeat it:

Lake City 2 with sling

This group was somewhat later.  My theory is that as the barrel of the rifle heats up, the pressure of the sling on the front of the hand guards starts to throw off the precision.  The alternative possibility is that the sling just adds another variable that I have to struggle with to keep consistent.

Aguilar 55gr.:

Aguilar 50m with sling

Not the worst ammo I’ve ever shot, but not the best either.  I took it out to 100m:

Aguilar 100m with sling

As bad as this is, it’s the best I’ve ever done at 100m.  What I don’t understand is how a 2 inch group at 50m became a 10 inch group at 100m.  I would think that simple geometry would give me a 4 inch group.  I’m going to try without the sling next time and see what happens.

4 comments:

Professor Hale said...

I do not use a sling in marksmanship. I know some shooters swear by it but I can see as you mention that they are another source of variability. In highly accurate rifles, the point of floating the barrel is that NOTHING touches it forward of the locking nut. If your forward sling mount is on the barrel (typically under teh forward sight post on an AR), then you are getting some intentional streatching of teh barrel.

I can't quite tell from your picture though if yours is mounted to the front of your handgard and if your handgard is floating. If that is the case, then, no harm done and sling away to your heart's content.

But the more things you have under tension, the more your muscle fatigue plays into it, thus the higher probability of loss of repeatability. Ideally, you want hte same result as if every round is your first round.

Good news on the sight.

Professor Hale said...

The value of a god sight is helping you to acheive a consistent point of aim. Not having on at longer range would contribute to the higher variability you are experiencing. As you point out, more than just mathematically expected.

Dr. Φ said...

Yes, the gandguards are free float, and the sling is mounted under the front sights.

I'll look have another post on Thursday where I do better.

Professor Hale said...

You could move the front sling mount to your handguard. There are plenty of rail attachments for that sort of thing. Floating handguard + tugging on the barrel with a sling defeats the purpose of the floating.