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Discussion Starter · #1 ·
I have an '03 springfield that I shoot 180 gr. sp through. If I change to a 125 gr. bullet with the horizonal POI change? The ballistic tables show that the bullets are with in a half an inch vertical out to 200 yards. I know I need to shoot it first but I am looking for a ballpark idea first?

skog
 

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You will almost certainly have to completely re-zero. Changing bullet weight will not only change the muzzle velocity and the ballistic coefficient (which affect the trajectory), but will also change the way the rifle recoils and twists.

A rifle starts to recoil well before the bullet leaves the muzzle, so a change in recoil will change the angle at which the bullet is launched. Also, depending on your grip and the way the rifle fits your shoulder pocket, it will change the way it moves laterally when the bullet weight is changed.

Also, the bullet is forced to start spinning when it hits the rifling... this exerts an opposing torque on the rifle, causing it to rotate very slightly. Changing the bullet weight (bet you can see this one coming) causes the rotation to change, affecting the zero.
 

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Discussion Starter · #5 ·
This afternoon I patterned it. The remington 125 gr. reduced recoil shot 1" lower at 100 yards then the remington 180 gr. sp. @200 yds it was just the opposite. Horizonal was the same for both bullets. Thanks for the help

skog
 

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skog,

If they were to run that 125gr bullet out at higher velocities, as is common with lighter bullets, the 180's would have shot much higher than the 125s. It is a good mix, that 125 light recoil and the standard 180...the velocities are such that you can shoot either and be close enough. :D

Real problems start when shooting SXS double rifles. :? They jump up and sideways. :roll:
 

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Most of the year I shoot a 165 gr hpbt through my 30-06. But during the spring when I might see more foxes and smaller game I use a 125 gr TNT. When I switch it requires that I totally resight, the point of impact will not only change vertically, but will move left or right as well.
 
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