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Have any of you seen "magic" like this?

 
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  #1  
Old 01-01-2009, 12:48 PM
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Have any of you seen "magic" like this?

In a recent read of one of the gun magazines a writer was talking about his 25 caliber rifle and how it magically shoots flatter than it should. I think it was a 25-06 with a 100 grain tsx.
He said he had it zero'd 2" high at 100 yds and at 300 it was still up 1" high and at 400 was down like 6". Someone ran a bc calculation and said the bullet seemed to be achieving a .800.

I'm not calling this a fib but was wondering if some of you long range guys can explain what's happening here or if you have a couple of matching stories with your rifles. Can some sort of scope cant or wierd barrel fitting phenomenon be at work? BTW the load he describes is really accurate so there is good bullet stabilization there.
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Old 01-01-2009, 01:29 PM
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Re: Have any of you seen "magic" like this?

Trajectories like this are possible if the scope is mounted high above the barrel. Running some rough calculations suggests that the trajectory you described would be possible with a scope that's mounted about 3.5" above the bore. For less dense air (less dense than standard sea level conditions) the height wouldn't have to be so much, maybe 2.0" for 80 degrees at 5000 ft elevation.
There is not as much 'magic' in shooting as commonly believed, although occasionally we come up against some real stumpers!
-Bryan
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Old 01-01-2009, 05:49 PM
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Re: Have any of you seen "magic" like this?

I agree with Bryan, and then that fellow that just shot the trajectories in the field goes home to his puter and adjust the bc to match the drops. The whole time he leaves scope height at the defalt setting of 1.5".
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Old 01-01-2009, 06:20 PM
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Re: Have any of you seen "magic" like this?

This is funny. I JUST got home from the range. One of the guns we tested was my Accumark 30-378. Since I have two I am setting this 30-378 up to be a point blank carry rifle. The new load is with 168 gr TSX's at between 3550 and 3590. Haven't averaged them yet. The scope is a XVIII 4.5 x 14 x 50 mounted 1.9" above the bore. Sighted in at 2 1/2" high at 100, it was dead on at 300, and only 2 1/2" low at 400. But it drops bigtime from there,, it was 19" low at 500. So I have what I wanted, a carry rifle that you shoot dead on to 400.

Jeff
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Old 01-01-2009, 06:46 PM
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Re: Have any of you seen "magic" like this?

Jeff, somwhere in that trajectory path your bullet is going to be at least 6-7 inches above your line of sight. I would shoot at 175,200,and225 just to see exactly what it is.
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Old 01-01-2009, 07:47 PM
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Re: Have any of you seen "magic" like this?

Quote:
Originally Posted by Coyboy View Post
Jeff, somwhere in that trajectory path your bullet is going to be at least 6-7 inches above your line of sight. I would shoot at 175,200,and225 just to see exactly what it is.
Coyboy,
I just ran it through my PC Ballistic program. But I always check in the field to be sure. It is pretty much spot on to 500 with a drop at 500 being 19.3". My actual group was under 3" and center of group was 19" low. You are right though, it does show a rise of 3.7" @ 175 yards. I went right from 100 to 300 so this is probably right. I will confirm next trip. Still if it will shoot with less than a 4" poi 400 I will be happy.

Thanks for pointing it out.


Jeff
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Old 01-01-2009, 09:16 PM
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Re: Have any of you seen "magic" like this?

I have experianced this myself. I had one load I tested and after I settled on it I zeroed it at 300 yards and took it to 600 yards for some longer range testing. I used my 3rd bar on my NPR2 reticle for 6 MOA of drop. I just wanted to get on my target backer so I could determine how much to bring it up knowing my group would be much lower than the bulls eye. After driving down to the target I saw the group in the very center of the target. I had just bought a new NF scope and was dertermined that the wrong size reticle was installed in my scope. After checking the scope for demensional accuracy I became a believer. My BC was off the chart. Something like over 1.000 for a 178 AMAX. Sometimes the sum of the parts balance out perfect and we see the impossible. It doesnt happen often but happens sometimes. Most of the time it is some other mathematical error. Sometime youre lucky. When the stars align, good things happen.

Jerry Teo has also seen similar results in a couple of his rifles.
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