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Two distinct groups with the same load - what's happening?

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Old 10-01-2017, 07:41 PM
  #1  
Typical Buck
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Default Two distinct groups with the same load - what's happening?

I was testing some loads in my Weatherby Vanguard 270 Winchester in preparation for deer season. While I'm not going to be shooting it, my younger cousin and sister will be taking it during rifle season. I've been having quite a few issues with the gun lately, though, and today was no different. Here's what's happening:



130 grain Hornady SST - 3.405" OAL
Remington case
53.0 grains IMR 4451
Federal Large Rifle primer
3,020 fps average, 6 fps s.d.



130 grain Hornady SST - 3.405" OAL
Remington case
55.0 grains IMR 4451
Federal Large Rifle primer
3,141 fps average, 18 fps s.d.

As you can see, I'm getting two distinct groups quite some distance apart. However, the individual groups are somewhat tight. In the top picture, the three-shot group was .835", while the three-shot group on the bottom was .740", both at 100 yards. On their own, they would certainly be groups to be proud of, but with the other two bullets grouping elsewhere, I can't be comfortable with these loads yet. There was no real pattern to how the bullets hit, either, and I let the barrel cool between shots, so I don't think barrel heating was the issue.

My question is, what could be causing this? I'm wondering whether I'm not holding the rifle consistently enough between shots. Additionally, I was using a Lead Sled, which I've heard isn't conducive to the best shooting. The way I see it, I have two options: make some loads I've confirmed are accurate and see what happens, or test these loads for accuracy again using my pistol rest and a sandbag to rest off of.

Last edited by TN Lone Wolf; 10-06-2017 at 05:55 AM. Reason: Mistake
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Old 10-01-2017, 08:19 PM
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Originally Posted by TN Lone Wolf
I Additionally, I was using a Lead Sled, which I've heard isn't conducive to the best shooting. of.
BS.

Some people have fear or anger with lead sleds. It just a rest. If you don't use a rest for checking loads or sighting in scopes, you are just arrogant fool.

Today I was sighitng in 45-70. Only 50 yards, I realize difference would be multiplied at longer ange. But I did my final shot with sand bags, Touching. I realize at longer ranges it may different.

Only difference is length of pull. Same as jacket, or not. But I hear so many people say you shouldn't use them, that probably have not used one, and may use some other rest themselves or sand bags.

Myself, I am behind my rifle, looking forward, shouldering the rifle.




I bought mine to check loads, leaving my ego aside. Saying that, I was dissapointed, that it was not rocksold steady. You still have to do your part. Is just a rest.

Mine only hold 25lb, depite claim of 50. But I like that, still gives you recoil.
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Old 10-01-2017, 08:22 PM
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All that aside, things effect grouping. I was having high shots with my new 45-70. My theory is heavy trigger is causing me to lift. When I shoot 30-06, I only support with one hand, often. With my 1895 I need to hold the forearm, or it seems to go high. Which I adjusted lower, only to be really low when shouldered tight.


No answer, just saying lot of factors
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Old 10-02-2017, 12:35 AM
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Next time use a marker and number the brass and keep track of where they hit in the groups !
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Old 10-02-2017, 06:31 AM
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Originally Posted by mounting man
Next time use a marker and number the brass and keep track of where they hit in the groups !
What do you think that will do? They measured the same, and same brand of brass.



Re-reading this in the daylight. Two groups, two different amoutns of powder. Hit 2 different spots. So? You would think it would just be elevation, in perfect linear world.

Ya I would expect a linear spread. Maybe pressure spike causing something different. Primers look good on both? High chargers racks out fine?

I have notcied groups tighten up at with certain charges in some rifles. My 45-70 actually changes elevatio with charge at 50. My 30-06 and 243 do not at 100 yards. They tend to change accuracy. 45-70 is more accurate then people realize. Doesn't seem to care how many grains, udner max of coarse.




Keep a log book, and document how your charges work for you. Find the best grouping. With a chrono people also look for consistent speed if shooting long ranges. Then sight your rifle in for the load you decided on. Just my opinion. But I am only on 2nd cup of coffee, in vacation.
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Old 10-02-2017, 07:00 AM
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TNLW,

I have seen something similar when someone was loading a bit too close to the lands and probably getting some pressure spikes. Also, sometimes different lots of bullets have very tiny variations from previous lots which can change max coal.

Your coal if fairly long, so I would try pressing the bullet deeper and see if that has any effect. Sometimes a bit of jump is not a bad thing.

Are you showing a six shot group with mixed results, or two three shot groups with different POI?
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Old 10-02-2017, 08:33 AM
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Originally Posted by Big Uncle
Are you showing a six shot group with mixed results, or two three shot groups with different POI?
Five shots for each load to be tested, with two of the shots hitting one place and three hitting someplace else. The other loads I tested weren't as accurate, but they had definite fliers.
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Old 10-02-2017, 01:32 PM
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I would hold the fore end during firing to see if you are having a simple problem with bag jump. If that is not the problem I would revisit the seating depth of the loads.

Good luck with it.
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Old 10-04-2017, 02:45 PM
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Before I would go and change anything as both those loads shoot good I would try a couple things. Next time out take another rifle along. Shoot this one then play with the other until you're good and sure this rifle has cooled down. Then fire another group and see where it hits. Should be the same as the first group. If not, give the barrel a good cleaning there at the range and try shooting again.
IMO its one of a couple issues: Either heating of the barrel or barrel fouling. (If its barrel heating make sure your barrel is free floating) It may also be that the action screws are not tight.
Maybe a bedding job is in order but try the simple things first.
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Old 10-05-2017, 01:38 AM
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Originally Posted by Big Uncle
TNLW,

I have seen something similar when someone was loading a bit too close to the lands and probably getting some pressure spikes. Also, sometimes different lots of bullets have very tiny variations from previous lots which can change max coal.

Your coal if fairly long, so I would try pressing the bullet deeper and see if that has any effect. Sometimes a bit of jump is not a bad thing.

Are you showing a six shot group with mixed results, or two three shot groups with different POI?
winner, winner, chicken dinner. group within the group syndrome can almost always be helped by adjusting seating depth.
RR
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