Question for precision shooters

[Lefty-Canuck]

Hi guys,

Quite often I run into an issue when test shooting where it almost looks like I have shot 2 groups when in fact I was aiming for same point. Below is an example.....

This target was 5 consecutive shoots taken off a bench rest from 200m.... So do I keep track of what bullet hit where and sort brass from there? Or is something else going on?

I was getting a bit of mirage off the barrel....but tried to shoot when it was minimized.

I realize there could be a tonne of factors but what would be your top 1-3 things to look at on this?



Any insight is appreciated. I run into this issue often enough to wonder if it is just me or how I load etc.

LC

[snroth]

Is your barrel floated good so that there is no contact when firing, or it could be that your cheek weld is changing.

[Lefty-Canuck]

Originally Posted by snroth

Is your barrel floated good so that there is no contact when firing, or it could be that your cheek weld is changing.

Yes barrel is floated back to a bedded action and bedded bottom metal....I think you might be onto something with the cheek weld changing!

The stock does not have a rise on the butt stock, will have to find a way to keep that more consistent....very good tip I often overlook...thanks!

LC

[Jordan Smith]

1. Scope/loose mounting system
2. Bedding
3. Load
4. Parallax issues

[catnthehat]

Inconsistent for will bounce them out of the group that far as well, so will a condition change.
Cat

[Lefty-Canuck]

Thanks for the comments. I definitely think the load has a huge potential!

I think that my form and setup could use a few improvements.

LC

[TriggerHappyHippy]

Parallax needs adjustment

[Lefty-Canuck]

I had adjusted the scope to the proper hash marks (front AO) for parallax....BUT I think that parallax and consistent cheek weld/ form is what is causing this. I just have to figure out a way to ensure consistency and repeatability.

LC

[TriggerHappyHippy]

In manyyy cases markings on the scope are not accurate
look through the scope and slowly move your head up in down, or side to side, while remaining looking through scope
if the crosshairs move on your point of aim, you still have not gotten rid of all the parallax
Adjust the parallax setting until your point of aim and crosshairs do not change as you move your head while looking through the scope

[TriggerHappyHippy]

I would say it has nothing to do with your bedding, or scope mounting
If the sequence of shots were different maybe
#1 and #4 are the same if it was heated barrel. or not free floating the shots would be in our, going away from the first..
I would say you have not got rid of all your parallax is right
each time you shot you looked through the scope you were in a different position in the slighttest bit therefore your point of aim was a little different too
ie: shots 1 and 4 you looked through it in the same position
Proper parallax adjustment rids you of this variable
dont go by what the marks on the scope say, adjust it as stated

[TriggerHappyHippy]

Or bad ammo..
lol

[Dick284]

My experiences with this is, first ensure a repeatable set up in the bags, same spot on the forend, and same position with your hand on the grip, same cheek weld, same tension into your shoulder. Make sure the recoil is predictable and repeatable.

If the above fails to change things, change primers and re work your load.

[ShawnM]

I wish there were more threads like this one.

If I started stringing them I'd look to my skill level but as to what it could be if you're skill is high I don't know.

[elkhunter11]

I had adjusted the scope to the proper hash marks (front AO) for parallax

The hash marks don't always match up properly for the distance. I adjust the parallax while watching the target, and ignore the hash marks. I did help one person out, who was stringing shots, because he didn't always have the fore end placed the same on the front rest. Sometimes, the front stud was resting against the front bag, and sometimes there was clearance. Verifying that the stud was clear of the bag for every shot, helped a great deal.

[fish gunner]

2" group 2" low and 1.5" left at 200 yards . I m not convinced it has any thing to do with the rifle. Roughly 1 moa. Is this a custom rifle . If the rifle has shorter than a 24" barrel length your golden. I'm betting you left handed.

[Lefty-Canuck]

Originally Posted by fish gunner

2" group 2" low and 1.5" left at 200 yards . I m not convinced it has any thing to do with the rifle. Roughly 1 moa. Is this a custom rifle . If the rifle has shorter than a 24" barrel length your golden. I'm betting you left handed.

Yes custom, 260 improved, HS precision stock. Lapua brass, 107gr Sierra Match King, 39gr of Varget, federal match primer. 26 inch heavy barrel. Group averages 3.5 inches low from point of aim...and yes a lefty

LC

[fish gunner]

Originally Posted by Lefty-Canuck

Yes custom, 260 improved, HS precision stock. Lapua brass, 107gr Sierra Match King, 39gr of Varget, federal match primer. 26 inch heavy barrel. Group averages 3.5 inches low from point of aim...and yes a lefty

LC

Sounds like a wonderful rifle congrats . Pulling into you cheek at ignition is my dollar. Try a group at 225 meters and again at 175 the results imo will show a similar change in moa form point of aim 4"at 225. 2 3/4 at 175. Do you have a reload that's driving tacks with the rifle.

[Lefty-Canuck]

Originally Posted by fish gunner

Sounds like a wonderful rifle congrats . Pulling into you cheek at ignition is my dollar. Try a group at 225 meters and again at 175 the results imo will show a similar change in moa form point of aim 4"at 225. 2 3/4 at 175. Do you have a reload that's driving tacks with the rifle.

This is same load...

Here is a 5 shot 100m group with the same load....when I switch from 100m to 200m I adjust the parallax as per scope hash marks but will need to pay more attension next time to whether the parallax is eliminated or not.



LC

[fish gunner]

Get into firing position and have a friend place a sand bag on your shooting shoulder .I'm not a reloader , is this a hot load for .260 as far a powder wt?? Have you checked your resting pulse. Sounds silly but it can be a factor if one is walking the range. That pic is 4 tacks and a 1" flyer. Fine shot placement.

[tchardy1972]

From the first post my bet was on parralax or bedding. Not to mention 200 yards is a lot less forgiving than 100 when it comes to shooting groups

[tchardy1972]

Originally Posted by Lefty-Canuck

This is same load...

Here is a 5 shot 100m group with the same load....when I switch from 100m to 200m I adjust the parallax as per scope hash marks but will need to pay more attension next time to whether the parallax is eliminated or not.



LC

Did you actually call that flier? You have to be dead honest with yourself when doing this kind of thing. Maybe its is something with the load.

[Lefty-Canuck]

Originally Posted by tchardy1972

Did you actually call that flier? You have to be dead honest with yourself when doing this kind of thing. Maybe its is something with the load.

The 100m group was yesterday and I honestly don't recall that specific shot feeling bad....the 200m shot was today and conditions were similar. I don't turn necks on my brass but I do periodically check for run out...I will have to check everyone before firing and see.

I wanted to confirm the load at further distance today so I shot the 5 shot at 200m today..... Will have to sit down next weekend with the same load and see what it does. This is not an overly hot load for the 260 improved and no signs of pressure from what I can tell.

LC

[DaleJ]

LC are you shooting from pedestal or bi-pod? Harris bi-pods shoot better with preload. How quickly are you getting the shot off. Sometimes too much time is taken trying to steady the crosshair on target. If you don't fire within a few seconds pull back from scope and let your vision normalize. If you're looking at the crosshair too long its placement becomes etched into your vision. Shooting with both eyes open will help.

Try shooting the rifle free recoil in a good set of bags. Don't touch anything on the rifle except the trigger. If that improves the group size return one step at a time to your standard shooting procedure to figure out what the rifle doesn't like about you.

Hate to mention this but Varget may not be the best choice for 260AI. In my loads Varget provides best accuracy when cartridges are full or slightly compressed. Not sure what barrel twist rate you have but if its 1:10 130's should work, 1:8 for 140's. Case capacity of the 260 AI should be about the same as the 6.5 Swede and they love R22 and IMR 4831.

[260 Rem]

If I had a definitive anwer to resolve "two group" syndrome, I'd be rich....because I would not have shot hundreds of groups trying to resolve the phenomenom. One of the likely suspects, parallax has already been mentioned, but if this has not happened with other loads, it is probably not the culprit. My top two guesses would be:
* load (either velocity variations or run-out)
* bedding (it is possible for the action to sit in one spot for a few shots, and then bounce back to another spot...like bouncing between two places if that makes sense?)
If "two group" occurs with different loads on different days, it is probably not the load. Sometimes a bit of tinkering with the torque on the action screws, sorts out issues...if the bedding is not right, it is possible to stress the action.

[Lefty-Canuck]

Thanks for the info Dale.

Rifle has a 1-8 twist rate.

I am using a Rock-BR front rest and an Edgewood rear bag.

I have tried h4831sc but the load is compressed and I don't get the accuracy out of the 123mk I was trying first.

Strangely my fireformig rounds using 100gr Sierra varmint HP flat base shoot sub-moa almost all the time with h4831sc. So I thought I would try the 107mk but they didn't do as well and I have Varget so I thought I would try it . So I shot the 100m group and it looked decent them I went back to 200m and experienced the "two group" thing going on.

I am taking some time for the shot and maybe I need to back out and retry....I always shoot with both eyes open.

I do have other powders on hand...

H4350
Rl17
Rl22
Varget
Imr4831
Imr7828
H4831sc and reg H4831
H4895
H322

I made this post not only in the hope to make myself more aware but also hoping other shooters can pick up a tip or two.

LC

[gopher]

Mark the hi side of bullet run out and chamber same way every time.

Chasseing ones ass with a semi-custom rifle never made much sense to me why not get a real bench rest rifle and do it right?

[fish gunner]

Originally Posted by tchardy1972

Did you actually call that flier? You have to be dead honest with yourself when doing this kind of thing. Maybe its is something with the load.

Did I fax pas?? . When the mans shooting 4 under a dime what else do you call the 5th?? A squeaker. 1/4 moa at 100 gives 1 at 200 . As stated I'm no reloader but I do shoot a little.

[twofifty]

What dick and elkhunter mentioned (forestock resting in the same way each time, and not having the front stud on, against or near the front bag) are both important considerations in vertical stringing.

I take both out of the equation by maintaining four fingers of clearance between the front stud and the front bag. It takes an instant to gauge the clearance with the non-dominant hand.

Lateral stringing:
Another thing to pay attention to is that the stock is perfectly centered between the rear bag's bunny or rabbit-ears. Anything less than centrered will see the recoil shift the gun left or right, which shifts the POI to one side.

Ladder test & barrel transit time:
Lefty, it might also be that your load allows barrel harmonics to release the shot near the top or bottom of barrel whip.

Perhaps shooting a 200m ladder test with loads that are lets say four or five 0.3gr increments below and above current charge weight (if pressures allow), would show whether slightly faster or slower velocities release the bullet nearer the middle of the barrel's vibration amplitude. Barrel transit time can have a big impact on vertical stringing.

[260 Rem]

Just another chirp to mention how important multiple 5 shot groups are as one could be easily fooled into thinking they had a good load with fewer to compare.

[Hotwheels81]

Random fliers can also be caused by seating depth... Try moving even .005 either way and sometimes you will find the 2 depths shoot into 2 distinct groups... Found Bergers to be rather picky on seating but SMK's haven't given me any trouble "yet"