Horizontal stringing?

[hlee]

Okay, I need some help here. I am shooting a LR308 (1:10) off of sand front and back from a bench. I am using Hornady Match 168 BTHP ammunition at 100 yards. When I break the shot I feel that I am squarely on the target, however, I will (more often than I would like) have 2 out of 5 shots 1" left or right of center (though in line vertically). The cartridges are singly fed to eliminate effects of loading from a magazine. And, I am making no effort to guide the rifle with my off hand, as it is being used on the rear bag. I had the same problem a week ago with a friend's bolt rifle in 22-250. Below are two targets from that session. The first was shot, then I made much more conscious effort to control my grip hand and shot the second group.

I am new to shooting a gas gun so and tips shooting it are appreciated. Also, the last target is one I shot with the LR308 shortly after I purchased it. Those are rounds 31-35 out of this gun- same lot of Hornady ammunition.

I don't have any pictures from my last range session. Thanks.

 

[sinister]

Re: Horizontal stringing?

Good grouping, and your vertical error is minimal -- good shooting.

What scope are you using, and does it have accommodation for parallax? Are you keeping your eyeball consistently centered with the scope's optical center and aligned with the scope tube, erector, and reticle?

You might also try different trigger control (perhaps not using your thumb), which may be introducing pistol-shooter error.

With a semi-auto rifle you have to be extremely mindful of follow-through as most hammer-style actions are slower than striker-fired rifle lock-times.

 

[Graham]

Re: Horizontal stringing?

Don't wrap the thumb around the grip; straight back on the trigger; and hold the trigger back until all three recoil pulses are over.

 

[hlee]

Re: Horizontal stringing?

The top two targets were shot with a leupold variX-II 3-9x44(?) on a browning X-bolt in 22-250. The bottom target was shot with my LR308 topped with a bushnell sportview 3-9 x(?) scope.

Moving my thumb from around the stock to not was the major change in the two top groups.

Neither scope has accommodations for paralax, however, the bushnell scope has been replaced with a tactical elite model with parallax adjustment.

After reading a few threads I believe part of my problem may be rifle cant. My scope sits pretty high above the bore on the LR308. Additionally, there is an optical illusion that makes what is actually level appear to cant somewhat to the left. As a result, I may be compensating by inadvertently canting the rifle to the right. I read another thread where a 5 deg cant was causing roughly 1/2 mil deviation left or right.

Thinking back to the session yesterday, when I really doubled down and focused on leveling the rifle I would throw a shot about 1" right. Anyway, I bought a scope level and I will install it level to the reticle and see if I can- at least- minimize the effect of scope cant on my rifle. It may not help, but it is a relatively inexpensive fix if it does...

 

[Graham]

Re: Horizontal stringing?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: hlee</div><div class="ubbcode-body">I believe part of my problem may be rifle cant.</div></div>Nope.

 

[fargo007]

Re: Horizontal stringing?

Resist the temptation to choke up high on the grip with an AR type precision rifle with the web of your hand like you would a pistol. Stay lower on it so that you are engaging the WHOLE trigger straight back. Make sure you are not pulling one corner of the trigger but the whole thing evenly.

These are more difficult to group shoot with. If you are messed up on the trigger of a semi, it will let you know tout suite. But backing into the problem from the other direction, that also makes them a valuable training tool.

--Fargo007

 

[sinister]

Re: Horizontal stringing?

Does your LR308 have a single-stage trigger, and if so do you know trigger weight?

 

[hlee]

Re: Horizontal stringing?

The gun still has the stock trigger, which is... undesirable. The pull is 6 3/4 lbs and is less than smooth. I spent a couple hours today- off and on to maintain focus- dry firing at a spot on a street light about 100 yards away. Without the recoil of the gun I found that (with the grip I was using) the fall of the hammer was moving the gun about 1" laterally at that distance. I changed up my grip so that I can more naturally pull the trigger straight back, which allowed me to drop the hammer without moving the gun. I'll be spending a lot more time at the range dry firing than I have in the past.

And, I've got a spiffy new scope level mounted on my scope too. This allowed me to find that what I think is level is actually canted to the right.

 

[CaliShooter]

Re: Horizontal stringing?

Horizontal stringing: pay attention to what ur doing with your rear hand and shouldering.

 

[Sterling Shooter]

Re: Horizontal stringing?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CaliShooter</div><div class="ubbcode-body">Horizontal stringing: pay attention to what ur doing with your rear hand and shouldering.</div></div>

Here's a list of possible sources for horizontal grouping, assuming the rifle is shouldered from the right shoulder:

High right shoulder,
High vertical position,
Jerking the trigger,
Varying head pressure,
Movement of the right elbow,
No stability of position (wobble),
Change in sight picture,
Failure to maintain proper sight alignment

Of course, horizontal stringing can be caused by not properly adjusting NPA; but, most often, inconsistent trigger control is the culprit. Dry firing can expose trigger control issues when follow though is executed, continuing to aim with trigger depressed until imaginary recoil has had time to subside.

Smooth trigger control is mental, a conscious effort to pull the trigger so as not to disturb aim. Preparation begins, when shooting an the AR, with a high firm handshake grip, like the one you would use to shake a child's hand. This will place the trigger finger straight off the trigger. Then, allowing the trigger finger to rest on the trigger where ever it is comfortable sets this factor of a steady position in place for smooth trigger control.

About the thumb, remember you are looking at a handshake not a strangle hold. The idea is to maintain control not muscle the firearm from the grip.

Unless you've got a GA trigger pay particular attention to what Sinister said about follow through. My own experience with the DPMS LR 308 with stock single stage trigger is that it can be managed but not without getting down to the sort of follow through you would need for a flint lock.

 

[RFtinkerer]

Re: Horizontal stringing?

I had trouble with horizontal stringing last year when I started HP rifle shooting. Off a bench, not really prone. It was caused by not squaring my shoulder correctly primarily or loading the bipod, trigger pull secondary. Of course my trigger was about 2 lbs so not as much contribution as yours would be. Cant has little to do with it at 100, unless you're shooting it 90 degrees like an OG.