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#1
09-22-2005, 06:55 AM
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ANOTHER sighting in question
.270win, 130gr. sierra btsp's(factory ammo).
if i sighted in to hit 1" high at 100yds, would that be my highest point of impact from 0-500 yards? do bullets really arch up before they hit where you're aming? at 1" hight at 100 yards, where would that put me at 200,300,400, and 500 yards? 
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#2
09-22-2005, 08:15 AM
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Well, bullets DO rise above the line of sight, but they never climb above the line of the bore. You can't see it because the angle is too small, but the bore of the rifle points well above everything downrange, while the sights point below that. So the bullet crosses the line of sight twice: once soon after it leaves the muzzle and once more when it drops through the line of sight again.
For an easier to grasp analogy, think of a bow and arrow. You look at your target (line of sight) over the arrow. The arrow points well above the target while you're holding the bow back (the bore). When you shoot, the arrow rises and then falls again to hit the target. But it never "rises" as high as it was originally pointed. Back to your load... Sighted the way you wrote, the bullet would likely hit as much as two inches high somewhere about 175 yards, which would be its highest point. It would hit "on" again about 225 and hit ever lower after that. At 500 yards, it might be 12 or even 16" low. (I didn't plug it into a ballistics calculator, just wagged it) Better would be if you sighted 2.5" high at 100. The bullet would never rise more than 4" above line of sight (aimpoint) and would be on again about 275, perhaps 6" low at 350.
__________________
Freedom of the Press Does NOT mean the right to lie! Visit me at my Reloading Room webpage! Get signed copies of my Vietnam novels at "Baggy Zero Four" "Mike Five Eight"
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#7
09-22-2005, 05:56 PM
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He means both. It'll cross (upwards) at 40 and the again (downwards) at 180, with a rapid fall after that.
Which is precisely why I recommend that +2.5" at 100 sight-in. The bullet will never be farther than 4" from your crosshairs from the muzzle to about 325 yards, give or take a few at that far end. Unless you're shooting at really tiny targets (like mice maybe) it isn't critical just exactly where you're "dead on". As long as the bullet is within a few inches of the crosshairs -up or down- you simply aim at hair. If the deer is so far away that you have to aim at air, I personally wouldn't shoot.
__________________
Freedom of the Press Does NOT mean the right to lie! Visit me at my Reloading Room webpage! Get signed copies of my Vietnam novels at "Baggy Zero Four" "Mike Five Eight"
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#8
09-22-2005, 06:54 PM
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http://www.federalcartridge.com/defa...g=27&firearm=1
This ought to solve all your problems. Just go to the particular bullet that you are using and click on the ''ballistics" button.
__________________
I like to shoot stuff.
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#9
09-22-2005, 09:56 PM
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federal lists the info but there pop up screen is to small to see the trajectories at the bottom.
the 130 btsp seirra is going at 3060 exackly the same as winchesters super x silver tip load 100yds + 1.8" 150 + 1.5 200 0 250 - 2.9 300 - 7.4 400 - 21.6 500 - 44.3
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#10
09-24-2005, 10:58 AM
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went and sighted in yesterday. got my POA at about 3" high of center at 100 yards with the .270
i realized i am not a good shot. i flinch too much. i was actually considering a .243 or 7mm/08 for lighter recoil. i ended up shooting around 12 rounds. might go back today and drop it down to about 2" above center.
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#11
09-24-2005, 11:24 AM
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3" high at 100 yards is what Jack O'connor used to recommend for most open country rifles.
You will be 4" high at around 175 yards, and on at around 250 yards. A few inches (1-3") low at 300 yards, and about 12 inches low at 400 yards. In other words, a center chest hold will work from the muzzle to 300 yards- not a bad way to zero for open country hunting.
__________________
“May we never confuse honest dissent with disloyal subversion.” Dwight D. Eisenhower "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter" George Washington Jack@huntchat.com
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#13
09-24-2005, 03:20 PM
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well my next question is, i have a black bear hunt tommorow morning. as most of you know shots a treed black bear are no more than around 30 yards give or take. will my 3" high at 100 yards be a problem? normally we take head shots. they have never failed in the past and when i zero for dead-on at 100 yards in the past i can aim where i want the bullet to strike. what kind of estimations and hold over/unders must i make?
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#14
09-24-2005, 08:05 PM
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Don't change a thing.
At 30 yards, you'll be within a few black hairs of where it's pointin' .
__________________
Freedom of the Press Does NOT mean the right to lie! Visit me at my Reloading Room webpage! Get signed copies of my Vietnam novels at "Baggy Zero Four" "Mike Five Eight"
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#15
09-24-2005, 08:07 PM
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i realy cant say,
put a fedw rds on paper and roughly adjusting the scopes gets me on paper at 100. another reason id rather be sited in closer to deazd nuts center bull at 100. way to many close shots to be 3"s high also i have never actualy shot groups at 25yds to compare to 100. but i do know that with my rifles sited in at 100 i tend to miss at half or closer than that. i dont know if thats because my mind tells me its an easy shot or because im shooting off because of being that close.
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