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Have any of you seen "magic" like this?

 
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  #15  
Old 01-02-2009, 07:00 PM
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Location: Michigan
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Re: Have any of you seen "magic" like this?

Quote:
Originally Posted by bsl135 View Post
Micheal,
I don't take your posts as argumentative at all. I know you're a knowledgeable shooter yourself and take your (and others) observations seriously. I'm here to learn just like everyone else.
Can you tell me about the particular barrel; was is a thick heavy bull barrel or a thin sporter barrel?

I'll tell you the one I'd really like to get to the bottom of is the phenomena where rifles group smaller in MOA at longer range than short. I've never directly observed this myself, however I did have a 7mm Rem Mag Sendero that 'seemed' to group ~0.75" at 100 yards and ~1.00" at 200, but of course the only way to know for sure if the groups actually 'converges' is to shoot thru two targets at once. There's just too much anecdotal evidence on this one to ignore it and I can't figure it out. My current hypothesis is parallax. Scopes that are properly adjusted for parallax at 200 yards will have some aiming error at 100 yards if they're not properly adjusted. I can't find anything physical to explain how a group of shots would converge in from all sides as range increases.

There are some unexplained things that happen, but rather than conclude that something unnatural is actually happening, I choose to accept that I simply don't know enough yet to explain everything and keep an open mind in search of the answers.

Take care,
-Bryan
Bryan,

I really appreciate your learned postings on ballistics. One thought I've had regarding better groups at longer ranges, was the possibility that aiming error was minimized at the longer ranges. Let me explain. If I'm shooting at a 1" dot at 100yds, I am using approximately a 1moa dot for aiming, if I take that same target and shoot at 200yds, I've just cut my aimpoint in half and have probably reduced my aiming error (from an MOA perspective) by a significant amount.

Just my thoughts. Here is some anecdotal evidence for you. I have a 7mm Rem Mag that is on it's second barrel. I shot the first barrel completely out and am probably 1/3 of the way through the second one (30 years worth of shooting). I currently have a load that will print under 1/2 moa nearly every time at 100yds. The best I've ever been able to do at 100 yards is just over 1/4moa. I recently shot a .267" group at 200yds with it, which is by far the best group that rifle has EVER shot (from an MOA perspective). I was aiming at a 1/2" square paster.

Anyway, that's how I explain it. Kinda reminds me of the quote from the movie "The Patriot" "aim small, miss small"

AJ
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  #16  
Old 01-03-2009, 01:22 PM
Lightvarmint
 
Posts: n/a
Re: Have any of you seen "magic" like this?

Quote:
Originally Posted by bsl135 View Post
Micheal,
I don't take your posts as argumentative at all. I know you're a knowledgeable shooter yourself and take your (and others) observations seriously. I'm here to learn just like everyone else.
Can you tell me about the particular barrel; was is a thick heavy bull barrel or a thin sporter barrel?

I'll tell you the one I'd really like to get to the bottom of is the phenomena where rifles group smaller in MOA at longer range than short. I've never directly observed this myself, however I did have a 7mm Rem Mag Sendero that 'seemed' to group ~0.75" at 100 yards and ~1.00" at 200, but of course the only way to know for sure if the groups actually 'converges' is to shoot thru two targets at once. There's just too much anecdotal evidence on this one to ignore it and I can't figure it out. My current hypothesis is parallax. Scopes that are properly adjusted for parallax at 200 yards will have some aiming error at 100 yards if they're not properly adjusted. I can't find anything physical to explain how a group of shots would converge in from all sides as range increases.

There are some unexplained things that happen, but rather than conclude that something unnatural is actually happening, I choose to accept that I simply don't know enough yet to explain everything and keep an open mind in search of the answers.

Take care,
-Bryan
Brian,

You can set up a return to battery rail gun and shoot it using the exact same point of aim and this eliminates the environmental mirage effects while aiming. Another point is that some folks shoot groups without mirage shades and that effects bullet impact points as well (I see this often at rifle ranges and it just kills me to see them actually sight their guns in on very hot barrels)....... But, even with all the tools, you still have to read the wind or shoot in a tunnel or a warehouse.

During benchrest matches, sometimes shooters actually perform better at 200 than say 100 yards. I don't know if it is all the distraction of hundreds of wind flags or just trying to thread the needle, but I have seen this many times. As a matter of fact, I just checked my "screamer" patch collection and associated targets and I have more at 200 than 100. Maybe it is just less pressure at longer ranges because the expectation is lower for smaller sized groups.........

BTW, have you guys shot any instrumental BCs with your new .338s yet?

Happy new year.

Lightvarmint
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  #17  
Old 01-04-2009, 08:52 AM
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Join Date: Dec 2002
Location: mathias wv
Posts: 985
Re: Have any of you seen "magic" like this?

Well yes, I've saw it, the first fall I worked with the 160 accubond at 3575 fps, I was consistantly shooting high, I checked and rechecked everything, measured my scope heigth with a dial caliper to get it as close as I could, went under the weather tower to calibrate my barometer to get it right.
sighted in at 300 yards and dial up for longer ranges I was always shooting high, rechecked the scopes tracking and return to zero, it was ok,
so I was shooting a 160 accubond with a published BC of .531, at 3575 fps, so I started bumping BC up in my program a lil at a time, the longer range impacts started down, at .62 they were impacting at POA.
Now I'm not a math whiz, not much of anything except a dumb wv deer hunter, But I'm claiming A BC of .62 for shooting a 160 accubond, why? cause I hit stuff, my last whitetail was taken at 1350 yards.


while we're on the subject, how do the makers standardise a BC , is it corrected for sea-level? what velocities do they shoot them? is it not true that bc does go up as velocity increases?
RR
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  #18  
Old 01-04-2009, 05:49 PM
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Join Date: Jan 2003
Location: The rifle range, or archery range or behind the computer in Alaska
Posts: 3,591
Re: Have any of you seen "magic" like this?

Quote:
Originally Posted by Ridge Runner View Post

while we're on the subject, how do the makers standardise a BC , is it corrected for sea-level? what velocities do they shoot them? is it not true that bc does go up as velocity increases?
RR

Depends on the manufacturer. Some use real firing tests. Others use formulas.
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  #19  
Old 01-04-2009, 06:35 PM
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Join Date: Jan 2008
Posts: 17
Re: Have any of you seen "magic" like this?

hay i have been diling with the same thing with the .277 140 gr berger bullets thay have a publshed b.c. of .509 whitch thay just droped to .487. my load is pushing it at a chrongraft 3110 fps and with all my shooting from 500 to 1070 yards it shows that i nead a b.c. of .590 i have double checked every thing to scope hight ect
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