Group size, shape, factors

[h20hunter]

Feel free to hijack with other pics and group questions.

6.5 creedmore
140 gr partition
39.0 gr h4350 ( 1 gr below max )
Hornady brass
Remington lrp

What typically causes a horizontal string? I covered my fouling shot, 9 shots horizontal string.

Also, I made sure the man bun was even....not off kilter pulling my shots in anyway.

[h20hunter]

Yes, pic is rotated goofy.

[Crunchy]

Confirm vertical or horizontal?

[Karl Blanchard]

Often times a perfect horizontal line like that is Parallax.

[h20hunter]

Got it. This rifle also is very light and even though the trigger is crisp its still heavier than I'm used to.

[jasnt]

Could be parallax or inconsistent cheek weld imo



What is Parallax?
By Earl Hines, Best of the West Master Gunsmith

When we talk about the accuracy of a shooting system, there is one element that most people know little about, don't understand, don't know how to apply, or don't recognize. Many people have indicated that they understand it but when asked, they give an inaccurate response. What I am referring to is that thing called parallax. What is it? How does it work? How do I adjust it? Is it important? How do I know when it's correct? And where do I start? All important questions. I will try to answer all these and more.

First, what is parallax? Parallax is having both the cross hairs and the target in the same focal plane so that no matter where your eye looks through the rear lens, the cross hairs do not change position on the target. How can that be accomplished? Well, modern scope manufacturers provide us with an adjustment mechanism on the opposite side of the right and left windage adjuster. Older scopes without this adjustable feature were parallaxed at a given distance. Depending on the manufacturer, they would parallax their scope between approximately 75 yards to 150 yards. At normal hunting ranges of the time, maximum of 3 or 4 hundred yards, the small amount of parallax was minimal (but still there).



Let’s look at understanding the concept of parallax. Look at the simple drawing in figure 1. In the center of the scope we have a cross, representing the reticle or cross hair inside your scope. On the left we have the part of the scope you look through, and on the right is our target. This being a simple drawing, we have no internal lenses or way to adjust for anything. If my position on the stock causes me to be absolute centered, then I would see along line “A” through the scope. If, for some reason my position causes me to look through the bottom portion of the scope I would see my cross hair on the upper part of the target, line “B”. That would be exactly opposite if I looked through the top of the scope, my cross hair would appear to be on the bottom of the target, line “C”.



So as you can see, by looking through the scope in different positions the cross hair would appear in different locations on the target. Now to apply this to shooting this simple system on a rifle, you can also see that if you were exactly in the center for 5 shots with a perfect rifle, your group would be acceptable and in the center of the target. Look at figure 2. Same rifle but this time your eye is at the bottom line “B”, and you fired 5 shots, again your group would be acceptable but at the bottom of the target because you would see the cross hair at the top of the target and compensate by moving your rifle cross hairs into the center of the target. Same for position “C”. But if you are not in the same position or on the same line every time, as illustrated in figure 2, your group would be much larger and you would be wondering where your accuracy was. That is why modern scopes have parallax adjustment capabilities.



When correctly adjusted, the internal workings of the scope will be able to focus both the target and cross hairs at the same time (on the same focal plane) without movement no matter where your eye is located. This would be correct parallax. Look at figure 3. Most scopes have this adjustable knob on the left side or your scope. There are numbers, varying anywhere from 25 ft. to the lazy 8, indicating infinity. These are “not” and I repeat “not” exact ranges that you can rely on to be accurate. They are approximations. So now you must focus the rear ocular (the lens that you look through to see the target) so that these numbers are close to the distance you want the parallax to be “free”. The term used when your scope is adjusted free of error or movement.



Start with your brand new scope. Turn the parallax knob to the lazy 8 position. Now go outside, with a clear blue sky preferably, point your scope towards the sky and turn your rear eye piece clockwise until it stops. Next, while looking through your scope, turn the ring counter clockwise. Turn the ring until the cross hair becomes crystal clear. Go slightly past this point and then back to insure that it is at the clearest point. At that point your scope is now adjusted to you and only you. The cross hair, being in focus, has been adjusted for your vision requirements to be correct for you. Now you can mount your scope on your highly accurate rifle and head to your favorite shooting spot and finish adjusting things.

If you are sighting in at 200 yards you need to secure your rifle on a bench using sand bags or a very steady bench rest and adjust your parallax knob to 200 yard setting. Position your rifle so that it is pointing at the center of the target when you let go of it. Now without touching your rifle, position your eye at a point so that you are looking through the very center part of the scope. This would be line “A” in figure 1. Now move your eye, not the rifle, up and down, side to side and 45 degrees in all directions. If the cross hairs move in the opposite direction on the target from your eye position, you are “out” of adjustment. To correct or to verify that you are in adjustment, turn the parallax knob either clockwise or counterclockwise a little. This does not take a great amount of adjustment. The cross hair will stop moving if you were out of parallax, or have greater movement if you were already in correct adjustment. The thing that you are looking for is no movement of the cross hair on the target.

If you have a rifle capable of shooting 1 inch groups at 200 yards, even with the most expensive scope in the world, your group size and consistency cannot be realized until your scope is adjusted for you and you understand parallax and adjust for it. Is parallax important? You bet ya. Your bullets will not go where you want them to until you have perfect parallax.

It is all very simple once you have seen improperly adjusted parallax and a parallax free scope setting. Remember, your rifle can shoot no more accurately than your parallax capabilities.
Just a thought for you. How many rifles have been taken to a gunsmith because the rifle “would not group”? You can bet many rebarrels, bedding jobs and such have been sold or charged for that only need parallax adjustment.

[Crunchy]

Dont most scopes have a paralax adjustment?  Mine, I just dial to the distance I am shooting.  Is there something more I should look into?  Just trying to figure out why my groups are sometimes inconsistent.  Shooting tight group one day, next trip lucky to shoot 1 MOA.  Same load data.  Probably just me but got me thinking. 

[jasnt]

Dont most scopes have a paralax adjustment?  Mine, I just dial to the distance I am shooting.  Is there something more I should look into?  Just trying to figure out why my groups are sometimes inconsistent.  Shooting tight group one day, next trip lucky to shoot 1 MOA.  Same load data.  Probably just me but got me thinking. 

distance numbers on your parallax are just aproximations. Never seen one that’s true to the numbers on the dial.  Many scope companies will call it focus but it’s more important than just focus.  The farther you shoot the less impact it has but at 100-200 yards it can make 1/4” in to 1.5” pretty easy

I’ve got in the habit of doing the head nod once natural point of aim is Acquired. If your cross hairs move around on target from moving your head and not moving the rifle than group size will suffer.  The article above explains how to set it properly and once set I’ll note in my head about how far off the mark it is so getting it set next time is faster.  After a while you’ll get to the point that you can range things less than 500 yards away just by setting your parallax.

[wooltie]

Could velocity changes cause vertical strings?

Suppose velocity does cause vertical strings.  If you chrono those 9 shots and the extreme spread was 10fps, then would you play with seating depth to resolve the string?

[jasnt]

Could velocity changes cause vertical strings?

Suppose velocity does cause vertical strings.  If you chrono those 9 shots and the extreme spread was 10fps, then would you play with seating depth to resolve the string?

velocity spread will cause vertical string at distance but not really a measurable amount at 100 yards, even 200 it’s not much even with a good size spread.  In my experience vertical stringing is caused by inconsistent loading of the bipod or shoulder preasure and gripping or poor rear rest all together, and cheek preasure.   

I like to free recoil for these reasons.  I’m most consistent when I do nothing at all ( little as possible).  I don’t load the bipod or lean in. I pull in to my shoulder just as hard as I squeeze the trigger and let the rifle do it’s thing.  For me it’s the most consistent method

[h20hunter]

@TRD1911

[Bigshooter]

What distance was the group?  If it was less than 300 yards forget about thinking about parallax. 

[h20hunter]

100 yards.

[Bigshooter]

What was your rest?

[h20hunter]

Sandbags front and  back, nothing touching the barell.

[Bigshooter]

Sandbags front and  back, nothing touching the barell.

Was your front swivel stud on the bag? or in front of the bag?

[h20hunter]

Nope. Settled in flush.

[BULLBLASTER]

I’d say natural point of aim, recoup management, or parallax are the culprit. Maybe a combination of them.

Parallax absolutely plays a role in accuracy at ranges closer than 300 yards. 

[h20hunter]

Thx. Have ten more loaded,  will focus on trigger and checking parallax.

[BULLBLASTER]

Natural point of aim is a big one for me it gets me if I’m not careful.
I like to line up and aim then close my eyes and take a breath and let it out. If you open your eyes and are still on target your good. If not adjust and try again.

[h20hunter]

I usually just line er up, squeeze my eyes tight and let er rip. I'll give that crazy method a shot as well.

[BULLBLASTER]

I usually just line er up, squeeze my eyes tight and let er rip. I'll give that crazy method a shot as well.

That’s a solid plan too! If all else fails get mad and grip it and rip it

Top group in this picture has horizontal stringing and was shot between the other 2.

[Bigshooter]

I’d say natural point of aim, recoup management, or parallax are the culprit. Maybe a combination of them.

Parallax absolutely plays a role in accuracy at ranges closer than 300 yards. 

Accuracy yes stringing them I don't think so.

[jasnt]

 @h2ohunter
Did it string them or just group a line?

[h20hunter]

Grouped a line id say.

[jasnt]

That’s says parallax to me. If point of impact just walked out the line then I’d say fundamentals or bedding issues. But if it grouped the line with one left then one right then one next to the left for example that very well could be parallax.  Next question would be is this a one time occurrence or does it happen more often?

[h20hunter]

First time for me....first 10 rounds of handloads. The factory ammo DID NOT group in this manner. Next set of 10 rounds should be very telling.

[wooltie]

Loaded up these at the flat spot. I'm going with the group on the far right, might have thrown that one round from the other three.  Will see what they group at 200/300 yards.

I shot these 12 shots plus one Fowler round robin style at 100 yards It was interesting to see the variation.

But if the far right group stays consistent then I'm done for this season!

[h20hunter]

Nice....heading out momentarily to test the next batch.

[Bushcraft]

What distance was the group?  If it was less than 300 yards forget about thinking about parallax.

Not so. Correct parallax adjustment is important at any distance for precision shooting.  It's the primary reason most shooters are baffled why their rifle shoots one day and doesn't another. You see it all the time at ranges. People think it's a focus knob...but as we know...it's not.

In addition to improper parallax adjustment, there could be some issues with his positional shooting fundamentals. You'll oftentimes see horizontal stringing like that in new shooters that are "bladed" to the rifle (and have developed a flinch) and/or are not engaging the trigger pull properly.

Also, I've seen some pretty insane horizontal shifts if the front action screw has worked loose. That cost me a spot on the podium at one-day PRS match earlier this year. I went from crushing every target to inexplicable horizontal impacts on the last three stages that I blamed on crappy wind calls.  Got back to the rig to put everything away for the trip home, and low and behold...I noticed the barrel was loose in the fore-end of the chassis and the front action screw was totally loose.

[kisfish]

tag

[h20hunter]

Didn't get pics but last rounds did not string.  Focused on focus, paralax, and trigger press. Groups were better but still not in love. Rifle and i can do better. Oh the pain ( fun ) !

[hunterofelk]

Barrel getting warm?  Might cause point of impact changes.