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5 shots 2 groups...help?

 
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Old 04-26-2013, 06:17 PM
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Location: Iron Range, Minnesota
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5 shots 2 groups...help?

So, I wanted to do some drop verification with my rifle today, since the weather finally wasn't freezing. I had just cleaned it, so prior to my test, I put 10 rounds through it to get it fouled. I shot those pretty fast, like 30 seconds between shots. i went and retrieved that target and placed a new one, 300 yards out through the snow. I got myself situated and fired the 5 shots I was using for my drop test. why 5? It's what I had and didn't want 2 random rounds left after my test.

I waited 2 minutes between each shot in the test. The mirage coming off the melting snow in the 65 degree weather sucked.

Here are the conditions:
Temp: 65
Pressure: 30.01
Humidity: 35%
Wind variable 1-5 from 5 o'clock
Sunny

Load:
Berger 155 VLD target
45.1 grains IMR4895
GM210M primers
Lapua .308 win standard Brass



Here is the target. I counted the 2 "groups" individually when I did the target analysis, but total vertical spread of 1.052 MOA.


my first thought was stringing from the barrel being heating up, but since it does appear to be 2 discreet groups, I am not so sure. I'll freely admit that shooter error might be the problem, just looking for other explanations before the verbal self abuse begins. Any thoughts or comments would be appreciated.
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Old 04-26-2013, 06:42 PM
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Re: 5 shots 2 groups...help?

A couple questions. If I read this right the total 5 shot group was about 3 1/4 to 3 3/8" Center to center? so just over 1 moa @ 300 yds with mirage?

That is not terrible and if the mirage was that bad , boiling up, it will add vertical to a group a lot of the time.

Jeff
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Old 04-26-2013, 07:15 PM
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Re: 5 shots 2 groups...help?

According to my OnTarget software, if I got it calibrated all right, the max spread is 3.38 inches, with 3.305 vertical.

This was my first time shooting with any Mirage, so I guess I'm not all that qualified to say how bad it was, but that aim point did seem to be bouncing around and disappearing a lot to me!

last fall when shooting, it was dry, and earlier this year, well, when it's 30 here, mirage isn't much of a problem.





on an interesting note, My recorded drop for the whole group is 10 inches, which, again, if I did this right, put my MV at 3000+FPS, depending on how much the mirage and my own abilities, factor in think I'm going to have to look really carefully at the brass.. and then tone down the load....the bolt lift was no harder than normal on my Savage
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Old 04-26-2013, 10:17 PM
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Re: 5 shots 2 groups...help?

I would shoot it again before I came to any conclusions. If it continues seating depth and bedding are two contributors
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Old 04-26-2013, 10:23 PM
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Re: 5 shots 2 groups...help?

Rifle has over 250 rounds through it. This is the first time it has happened. Will re test...the seating depth has been good in the past too
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Old 04-27-2013, 08:11 AM
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Re: 5 shots 2 groups...help?

Just out of curiosity - what scope and power setting were you using? That explanation of mirage seemed pretty bad for a distance of 300 yds.

Bottom line: I agree I would shoot it again before jumping to any conclusions. Although it seems we are always in a hurry, some days we would be better off to just go home when conditions are not good while load developing.
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Old 04-27-2013, 08:28 AM
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Re: 5 shots 2 groups...help?

Quote:
Originally Posted by cowboy View Post
Just out of curiosity - what scope and power setting were you using? That explanation of mirage seemed pretty bad for a distance of 300 yds.

Bottom line: I agree I would shoot it again before jumping to any conclusions. Although it seems we are always in a hurry, some days we would be better off to just go home when conditions are not good while load developing.
scope was on like 16X, it's a Viper PST 6-24, they also have glare issues, and don't handle mirage too well. Normally up here I don't get much mirage, but with the 60 degree temps and snow melt, it's been kind of bad lately.

Today is cooler, and I'm going to get to the range before it heats up too much and see how it goes, I have a feeling that after not shooting for a while, my excitement at shooting played a factor.
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