Interesting video on POI shifts from various possitions

[Cap]

This isn't good. What worries me is not the POI shift using the barrel for support. WHat worried me is the difference between the tube, magazine and unsupported positions. Looks like at least a 4moa shift between the three. The targets are only at 50yards

The question it raises is, how do you combat this?

Here is the thread I found this on: My link

[rlc9194]

The shift is most likley caused by parallex If your heads not in the same spot every time you change positions your POI will change

[Religious Shooter]

I don't know...

There's going to be a difference with him laying the comp directly on the case like that. But I doubt it's going to be that big of a difference at 50 yards.

I don't want to insult the guy, but either the gun is messed up or it's the shooter.

[Nuke8401]

Not the first guy to ever shoot a tacticool AR who couldn’t shoot.

For resting the comp on the case; either the comp is loose or the barrel nut is loose.

David E

[Graham Smith]

Virtually the same discussion on another forum

[AlamoShooter]

What is that ? a 16" barrel with a 16 power scope? And 50 yards ? is it a northstar scope?

Edited December 17, 2011 by AlamoShooter

[ac4wordplay]

... is it a northstar scope?

That's pretty funny coming from you --> he's using a Vortex !

[Cap]

Not the first guy to ever shoot a tacticool AR who couldn’t shoot.

For resting the comp on the case; either the comp is loose or the barrel nut is loose.

David E

From what I understand he shoots for AMU. So that first theory may not be sound.

[AlamoShooter]

... is it a northstar scope?

That's pretty funny coming from you --> he's using a Vortex !

Dang I couldn't see that

Their I go with a big mouth full of dumness

Edited December 18, 2011 by AlamoShooter

[Gdaym8]

Very interesting results with the different ammo. Nice discussion topic.

[MstngLX50]

That seems about right to me.

I see about a full mil(3.6" at 100) to 12 o'clock with a medium contour when resting directly on the barrel. More with a lightweight barrel.

If I'm careful and keep the location of the barrel and the body position the same each time I can get a decent group. Changing the pressure on the barrel by allowing the handguard to make contact or adding/removing pressure gives me vertical stringing.

[DEP44]

I had a Steyr STG58 (FAL) and the difference at 50y between using the std bipod and using a sling was at least 1 foot.

Just saying.....

[Religious Shooter]

If you guys go to the link on the OP, he tests an A2 with handloads. He shoots it with the rifle 1) resting on the magazine, 2) slung and 3) with the barrel on top of an ammo can pressing down on the handguard.

There is virtually no shift with the A2.

If you are getting shift like the video on the OP at 50 yards... check your gun/mount/optic or technique.

[Alaskapopo]

I do know that back when I had a non free floated two piece rail set on a Colt I owned I could use the vertical foregrip I had at the time to move the point of impact 4 inches lower at 100 yards just by pushing the VFG harder into the bag.

Pat

[AlamoShooter]

I wonder how many of us has plans to go to the range with Video camer and burn up amoe. it would be good to know though. We left a stage at one event after using a V in tree limbs that put the hand guard in a bind and we were convinced that it was the "bind" that caused the missing.

with free float hand guard that doesn't sound rite though

[Jesse Tischauser]

This isn't good. What worries me is not the POI shift using the barrel for support. WHat worried me is the difference between the tube, magazine and unsupported positions. Looks like at least a 4moa shift between the three. The targets are only at 50yards

The question it raises is, how do you combat this?

Here is the thread I found this on: My link

What this dood does doesn't worry me. What would worry me is if my POI changed from those 3 positions. I'm glad mine doesn't!

[ken hebert]

are y'all seeing something i'm not? cuz i'm seeing a guy shoot a fairly good group from prone supported, then a decent group prone off the mag and the same thing from prone + elbows, and then a crappy stringing really high group (i use group loosely here) when he's torqueing the barrel UP. i'm not really seeing anything we don't already know here. i shoot tighter groups when i'm bagged up vs. free hand, and we all use FF handguards and dont rest the barrel on objects because of the POI shift. DUH!

[Jesse Tischauser]

Crap now I actually watched the video. This guy obviously can't shoot. Ken hit the nail on the head. If your supported groups POI at 50 are that much lower (not tighter) than your supported groups you are jerking the trigger and/or anticipating recoil. The last group that he strings up in a line was from his fat a$$ getting lazier and lazier while he lets his weight push his rifle down harder and harder while his barrel that is touching his case (not his 15" FF hand guard) gets pointed higher and higher.

[AlamoShooter]

But its on a Video .... ...It must be rite

[Religious Shooter]

He can shoot. Look at his A2 video.

[MustangGreg66]

He can shoot. Look at his A2 video.

Think about it for a second. With an A2, regardless if you have a free floated barrel or a standard A2 setup, for the A2 irons, the sighting system you're using is a front sight attached directly to the barrel. No matter which way you torque or flex the barrel, the sight is going to go with it. With the scoped test, the sight is a scope that is attached to the receiver. As the barrel flexes the scope stays in the same place, thus the dramatic POI shift.

I've seen this happen with guys in matches, shortish FF rail and a scope, they rest the barrel on a prop and it doesn't matter if they're shooting at 50,100, or 200 at whatever target, they're not going to hit where they're aiming. Hard to watch really.

Edited December 26, 2011 by MustangGreg66

[MustangGreg66]

as for the OP, any pressure you put on the rifle anywhere can effect your POI. Benchrest and long range shooters argue over how much head pressure, how tight to grip the gun if at all, shoulder pressure. All kinds of factors. If you put pressure on the forend, it's going to effect the gun, the forend is still attached to the barrel nut, so that downward pressure on the forend caused it to be a little high. When he magwell gripped it, his support hand was around the magwell so almost no pressure was on the forend, so he shot a little low compared to resting it on the forend. When he supported it on his elbows it looked like he was basically cradling the gun, no undue pressure anywhere so it went in the same place as the magwell hold.

That may explain it, but I was still in the camp of, it's a FF rail and nominal pressures on the rail should effect his POI... makes me want to go test mine a little more now to verify.

[Religious Shooter]

Think about it for a second. With an A2, regardless if you have a free floated barrel or a standard A2 setup, for the A2 irons, the sighting system you're using is a front sight attached directly to the barrel. No matter which way you torque or flex the barrel, the sight is going to go with it. With the scoped test, the sight is a scope that is attached to the receiver. As the barrel flexes the scope stays in the same place, thus the dramatic POI shift.

Huh?

If your reasoning with the scope is that it stays in place because it is on the receiver... Well the rear sight is on the upper receiver?

The rear-sight isn't realigning itself when you push on the barrel.

[George]

Think about it for a second. With an A2, regardless if you have a free floated barrel or a standard A2 setup, for the A2 irons, the sighting system you're using is a front sight attached directly to the barrel. No matter which way you torque or flex the barrel, the sight is going to go with it.

Not so, I know for a fact that at 200 yards the sling tension when shooting prone versus a neutral offhand hold is worth 4 clicks of elevation and 2 clicks of windage to get the same POI. This is using a Colt A2 HBAR 20" with non-FF HG. My free-float HG irons AR exhibits no detectable POI change at 200 yards with high sling tension on HG versus neutral hold.

[MustangGreg66]

Think about it for a second. With an A2, regardless if you have a free floated barrel or a standard A2 setup, for the A2 irons, the sighting system you're using is a front sight attached directly to the barrel. No matter which way you torque or flex the barrel, the sight is going to go with it. With the scoped test, the sight is a scope that is attached to the receiver. As the barrel flexes the scope stays in the same place, thus the dramatic POI shift.

Huh?

If your reasoning with the scope is that it stays in place because it is on the receiver... Well the rear sight is on the upper receiver?

The rear-sight isn't realigning itself when you push on the barrel.

True, but for irons, the front sight does move. When using iron sights you're really lining up 4 things: Your eye, rear sight, front sight and target. If you rest or torque the barrel on something, the front sight follows it because it's attached so you're just lining everything up along a diffrent path.

now imagine you had a rifle with a sling attached to the barrel or you're resting and putting pressure on the barrel BUT the front sight is on the end of a FF rail. The sights would remain in the same place but the barrel would be flexed in a diffrent direction. If you have a AR with a FF rail go see for yourself. You can put pressure on the barrel and actually see the barrel flex and the FF rail stay pretty much in the same spot.

Think about it for a second. With an A2, regardless if you have a free floated barrel or a standard A2 setup, for the A2 irons, the sighting system you're using is a front sight attached directly to the barrel. No matter which way you torque or flex the barrel, the sight is going to go with it.

Not so, I know for a fact that at 200 yards the sling tension when shooting prone versus a neutral offhand hold is worth 4 clicks of elevation and 2 clicks of windage to get the same POI. This is using a Colt A2 HBAR 20" with non-FF HG. My free-float HG irons AR exhibits no detectable POI change at 200 yards with high sling tension on HG versus neutral hold.

OK, ok you got me there. You're right. There's going to be some POI shift if you do this without a FF rail.

Geoff, this got me to thinking about your prone method of monopoding off the magazine AND pushing down and back on the FF rail. I wonder if that gives any flex to the system. I'll have to test it at 200 and see what comes out. For long range stages you're almost always braced diffrent: Prone, sitting, rooftop, through a window.... I'll have to test myself with my rifle to see if I get any shift with the diffrent positions and pressures on my rifle.