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Horizontal Stirnging

Okay guys. This is a duplicate post that I had on another forum board and I haven't any answers there so, here it is.

I'm going to presume it's a load issue with 2 different rifles. Here it goes...

I went out at 200 yards to test some loads and see what would happen with seating depth changes. The first picture was shot "round robin". I would shoot one round that was 0.005" off the lands and then progress until I had shot all 4 loads ending at 0.020". I adheared to a 2 minute shot interval. The next round was shot from right to left etc...

Between the 5 total shot stings, I would shoot groups with the 260 (which we'll get in to next). Here's the results with the first rifle.
1331601344.jpg

The issue I have is the horizontal stringing in the first group shown which is 0.005" off the lands. Vertical C-C is less than 0.45" Horizontal is 1.3". All the other groups look "similar" although terrible.

My 260 has 2 group that show similar results on groups #5 & 6. The groups were shot left to right, 5 shots at a time with ~10 seconds between shots. I varied charge weight and OAL on these groups but when the vertical went away, the horizontal gets excessive.
2012-03-12_14-11-06_202.jpg

Vertical on #6 (C-C) is ~0.16", Horizontal (C-C) ~1.6".

Since the groups in the first pic were shot round robin, and the groups in the 2nd pic were shot in "groups", I know that wind is not the issue. Anybody care to tell me what's going on here and where I need to go for correction?

The first rifle is a single shot and there is much more time between shots. Cheek weld is not maintained during the exercise. With the second rifle, I maintain my cheek weld due to the rifle being mag fed and there is much less heat generated. Each group is shot in approximately 3 minutes total. The rifle was allowed to cool ~5 minutes and then the second goup was fired. Once the 2 groups were fired with the 260, I would pick up the first rifle and then fire another round of my "round robin" testing. Both rifles were fired prone off of bipods and rear bags.

Target one ammo was loaded with Neil Jones custom dies on an RCBS. Target one brass was neck turned (twice), annealed, trimmed, primer pockets uniformed, brass within 0.8 gr of each other, powder was thrown with a chargemaster then weighed on a beam scale. The bullets used for each 5 shot loading were measured from ogive to base and were within 0.0015" of each other.

Target 2 ammo was loaded with RCBS bushing sizer, Forster Ultra seater and used a Co Ax press. Brass was turned, trimmed, sized and loaded. Nothing special was done here.

If you need any other information, please let me know. Thanks.
 
Bipod. What kind, and what technique? Are you loading the bipod or letting it slide? I know of a few that can cause vertical or horizontal.

Here is what I'd do:

Go back and shoot #1 on the #1 target, and #6 on the #2 target. See if you have horizontal stringing again. If you do, shoot the rifle off of the bags and see if it goes away. There is a real-world reason why
the F-TR national records are below the F-open records at short range. Very little of it is ballistics...
 
variation in wind velocity anc change from 3-5:00 can do this as well as change in cheek presure.

Mirage would give you some vertical shifting to low or high with the wind. so it looks like little mirage was involved

Bob
 
dmoran said:
You give great particulars to every thing but the wind !!!!
My assessment is: I see great accuracy in your targets, with a lot of wind related horizontal dispersion.
The reason I don't think it's wind related is the different way both targets were shot. The top target was shot round robin. Total time to shoot all the hole in the top target was ~ 2 hours. I started with the left dot, shot right and then I went and shot the other rifle. When I came back to the top target, I started on the right dot and then shot left. When that string was done, I shot the other rifle, etc, etc. If it were wind, all the groups should have shown the same stringing. I made an initial correction of 0.1 mil left because there was a 8-10mph L-R wind blowing when I was standing. I NEVER MADE ANOTHER ADJUSTMENT so, the wind should have been a constant in all the targets.

The second target was shot in 5 shot groups. I started with the left dot and shot all 5 of those particular rounds. I would shoot 2 5 shot groups and then pick up the first rifle again. The first four targets have more vertical than horizontal. It's the final combination in groups 5&6 that drops the vertical and picks up the horizontial.

Busdriver said:
Bipod. What kind, and what technique? Are you loading the bipod or letting it slide? I know of a few that can cause vertical or horizontal.
Both are Harris bipods with "Pod Claws" and it is lightly loaded. All the shots were cleanly broken. The trigger release is the same for both rifles but the timeframe for shooting groups is totally different. The rifle for target 1 had a 2 minute wait between loading rounds. My face came off of the rifle between shots. The rifle for the second groups was shot where I kept a cheekweld for the entire group. I never quit looking through the scope. It was a nice day so, I was comfortable.

bheadboy said:
variation in wind velocity and change from 3-5:00 can do this as well as change in cheek presure.

Mirage would give you some vertical shifting to low or high with the wind. so it looks like little mirage was involved
There was mirage and there was a difference in technique and cheek pressure since they were 2 different rifles shot in 2 totally different ways.

What I'm getting at here is that both targets (sheet 1 and sheet 2) have targets with horizontal stringing. Since the top target was shot "round robin" and shows a horizontal group and the bottom target was shot as "5 shot groups" and has 2 different groups showing the same stringing. What is the cause?
 
If you have Paralax adjustment, adjust that until you have zero paralax at what ever yardage that you are shooting, if not...your eye position in relation to the scopes exit pupil must be exactly the same each and every shot, without proper technique, your results will always be unpredictable.

The first thing that I would do is to start at 100 yards and stick some wind flags out! Use wind flags every group...and look at them before every shot.
2. Shoot 1 3 shot group with a particular load *including powder, bullet weight/make and seating depth.
3. move to target two and vary either the powder charge or seating depth, preferably the powder charge.... and continue to do so until you have the least verticle stringing.
4. Once you have accomplished this, fine tune your seating depth until your groups start to expand...that goes for closer to jam and farther away from jam....One direction at a time.
5. Use wind flags every group...and look at them before every shot.
 
Had similar issue with my 260. I fixed it by getting a smaller bushing. Tried 2 smaller bushings and found the right one. No more vertical and horizontal. Started shooting tight 1"-1.25" groups at 300yds. Nice tight looking groups too.
 
Many times there are no easy and quick answers. A good rule of thumb that will serve you will however is Vertical stringing is ""Usually"' the load, Horizontal stringing is almost always the Shooter or the wind.

There are a few mechanical problems that cause Horizontal, Bedding issues etc but almost always it is Technique or wind. It can be as simple as the "way" you pull the trigger as an example. As to the wind without wind flags and being able to read those flags you really don't have a clue as to what the wind is really doing......

Roland
 
Horizontal is probably you. If the trigger pull is right then the cheek pressure can make the shift happen. I've been working that out of my shooting in the last few months, but I still do it from time to time. When your cheek lets off the stock the back of the rifle moves left (assuming you are righty) and the impact moves left.

Try to get a NPA that is steady on the center with very little cheek touching then break the trigger.
 
IF it IS ME as a shooter, I still have a difficult time explaining the string when shooting both round robin and traditional groups. I don't think it me OR the wind.

If the issue were me, I would expect to see the issue in all 4 top groups and all 6 bottom groups.
 
I am sure some will differ with me on this, but I have always believed (based on my own personal observations) that some loads are more prone to horizonal stringing, some are more prone to vertical stringing, some are more prone to horizontal stringing and some behave better based on barrel harmonics.
 

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