Marksmanship Advise

[plinker]

This weekend I zeroed in my .308 w/ Bi-Pod at 50yrd, nice group in the 10 ring. I moved over to the 100 yrd targets with same set up and ammo and started to group in the 7 ring, directly above.

This was a seated bench, is it possible that my positioning and/or check weld changed enough when I moved lanes to cause the rise in the impact point. Was I flinching on the 100yrd? Any advise on what causes rise in the impact point at longer distances?

Thank you

[bobfried]

Ballistics and trajectory.

A bullet doesn't fly straight like a laser does. It exits the muzzle, goes up through an arc than drops down as you go farther out.

You need to do a search on ballistic charts and learn where a bullet will strike. For example, .308 will hit 4" below POA at 200 yards if you zero at 100 yards. etc. etc.

[Prc329]

This weekend I zeroed in my .308 w/ Bi-Pod at 50yrd, nice group in the 10 ring. I moved over to the 100 yrd targets with same set up and ammo and started to group in the 7 ring, directly above.

This was a seated bench, is it possible that my positioning and/or check weld changed enough when I moved lanes to cause the rise in the impact point. Was I flinching on the 100yrd? Any advise on what causes rise in the impact point at longer distances?

Thank you

As the previous poster said the bullet travels at an arch. You would need to re-zero at 100 yards or use a ballistics chart to tell you how to set your scope to hit the x ring at 100. You really should zero your rifle at 100 yards though.

[plinker]

Thanks for the quick advise on both replies, I always assumed the trajectory stayed level and eventually dropped after leaving the muzzle.

[redcliff]

While bullets certainly have a trajectory and arch, you're seeing the effect of the difference in height and angle between the sights and the bore.

When you line up the sights on a target at 50 yards, the barrel has to be pointed up to intersect your line of sight.

When you moved the target back to 100 yards your 50 yard zero caused the bullet to pass above the sight plane and strike the target high.

By doing a battlesight zero at 25 meters, you'll also be fairly closely zero'd at 300 meters. Bullet path and line of sight intersect at 25 meters, then the bullet climbs and arches down again to intersect your line of sight at 300 meters.

[bobfried]

While bullets certainly have a trajectory and arch, you're seeing the effect of the difference in height and angle between the sights and the bore.

When you line up the sights on a target at 50 yards, the barrel has to be pointed up to intersect your line of sight.

When you moved the target back to 100 yards your 50 yard zero caused the bullet to pass above the sight plane and strike the target high.

By doing a battlesight zero at 25 meters, you'll also be fairly closely zero'd at 300 meters. Bullet path and line of sight intersect at 25 meters, then the bullet climbs and arches down again to intersect your line of sight at 300 meters.

Your partially right but mostly wrong. It has more to do with the bullet than with the barrel to sight relation. Matter of fact it's mostly all about the bullet trajectory.

And you have a very basic understanding of zeroing a rifle. What you quoted only works on an M16A2 shooting M855 and using a 25m target made specifically for mil-qualification. You are stating a zeroing method for a very specific rifle shooting a very specific bullet. If you are doing this with every rifle you own than you need to re-zero them depending on their caliber and weapon's type.

The OP is shooting a .308 rifle which has very different trajectory.

You need to zero at 100 yards, than create your own trajectory chart for 200, 300, 400, 500 and so on.

[BP88]

A rise in impact is usually your breathing. Try shooting at the top or bottom of your breaths.

I'm not the best shooter in the world by far, but that's what they taught us in Army basic and I sure as hell qualified. :]

[ocabj]

redcliff is absolutely correct.

The reason why a bullet appears to climb as it exits the muzzle isn't because it magically climbs. It's because the axis line of the bore isn't level with the ground. If you draw a line through the axis of the bore and a line through the axis of the sights or scope, the line of the bore will not be level with the ground, nor will the line through the sights.

The axis of the bore will actually be a line with an inclining angle to the ground.

This isn't sci-fi. Bullets have to follow the laws of physics. Bullets come out of the bore at level flight *with respects to the axis line of the bore* and immediately begin to drop.

When you are firing any projectile, you are basically lobbing the bullet to the target, just like throwing a football.

The axis line of the bore is never going to be parallel to level ground (when shooting at a target at relatively equal height of the shooter).

[redcliff]

Your partially right but mostly wrong. It has more to do with the bullet than with the barrel to sight relation. Matter of fact it's mostly all about the bullet trajectory.

And you have a very basic understanding of zeroing a rifle. What you quoted only works on an M16A2 shooting M855 and using a 25m target made specifically for mil-qualification. You are stating a zeroing method for a very specific rifle shooting a very specific bullet. If you are doing this with every rifle you own than you need to re-zero them depending on their caliber and weapon's type.

The OP is shooting a .308 rifle which has very different trajectory.

You need to zero at 100 yards, than create your own trajectory chart for 200, 300, 400, 500 and so on.

I'm sorry, I missed that he was shooting a .308 it was late and most of the questions we get are about OLL ARs

Yes the battlefield zero I mentioned is for an AR15 type rifle. My .308's are zero'd correctly I think, as I"ve shot in several long range precision matches; the last one had 3" targets at 500 meters. I may need to work on my zero and shooting skills though, as I only placed 3rd, although the 30+ mph gusting wind and driving rain may of contributed to that. I do in fact carry a ballistic trajectory chart in my wallet for my 700pss with 168 gr Federal Gold Medal Match.

However as Ocabj stated I'm not wrong regarding sight plane versus bore axis and it's effect.

[Solidsnake87]

Try these things in order.

1.) Take a deep breath and release half of it before firing
2.) Are you anticipating the recoil? Relax and just pull the trigger
3.) When you pull the trigger, are you also moving the rifle? practice pulling the trigger straight back and not moving the rifle
4.) You have a bipod, how do you stabilize the back end? Try a bean bag, range bag, or monopod
5.) Get a two stage trigger with a light 2nd stage
6.) learn to use a sling
7.) Are you using an optic? If you are, is it of decent quality? A good scope has clarity and mantains excellent tracking. Try a basic Leupold or mid-range Nikon/Bushnell to get started.

For best results, try different types of quality ammo to see which works best in your rifle. You might even want to pick up handloading!

[Pthfndr]

Try these things in order.

1.) Take a deep breath and release half of it before firing

How much is a "deep breath"?
How do you know that you've taken in the same amount of air each time?
How do you know your muscles and diaphram have worked the same amount each time?

When you release "half of it", how do you measure how much you release each time?
How do you know you stopped your muscles and diaphram at the same amount of tension each time?

Breath normally. During normal breathing your body has 2 natural pauses. One on inhale, one on exhale. When you inhale your muscles are working. When you exhale, your muscles are at a natural point of relaxation. Guess which point is the best one to pull the trigger.

ETA: This not just my opinion, but that of the best long range shooters and instructors out there.

[ar15barrels]

[BP88]

You can get all scientific but trigger squeeze and most of all in this situation - breathing control, makes a bigger difference at longer ranges. Try practicing more and you'll get the hang of it. I'm not that great a shot but I notice when I practice my breathing skills and trigger squeeze I'm more consistent on the target. Oh yeah, I shoot with irons too, until my Aimpoint mount comes in.