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I have a Savage bolt action Model 110 .270 Caliber Centerfire Rifle and a Nikon Prostaff 3-9 x40 with the BDC Reticle what mounting base and rings should I use?
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Step 1
Take a rifle with a properly installed BDC bullet drop
compensating reticle to a rifle range. Using ear protection zero the
scope reticle so that the point of impact corresponds to the center of
the cross hairs at the distance you have selected - typically 100 or 200
yds.
Step 2
Determine the trajectory of the specific cartridge you have
selected. There are several ways to do this. Ammo manufacturers publish
trajectory and wind drift information. There are web based ballistic
calculators like http://www.biggameinfo.com/BalCalc.aspx which will tell
you how much your bullet drops at known distances.
Step 3
Scope manufacturers like Leupold can be a valuable source of
information about their reticle: "Leupold® Ballistic Aiming System:
Boone and Crockett Club® Big Game Reticle aiming system provides a
series of additional aiming points to improve your ability to shoot
accurately at longer ranges. Nikon
also provides good information suggesting the marks on their reticle be
used for zero at 100yds followed by circles below representing 200, 300,
400 and 500 yds if the cartridge travels around 2800 ft per sec. Nikon
suggests the center cross hair be zeroed at 200 yds for magnum calibers
traveling around 3000 ft per sec. We understant that each variation of
different bullet weight and powder charge changes trajectory and a scope
manufacturer can not build a different reticle for each different
cartridge made so practice on the range to determine how well the marks
relate to the actual impact of where your bullet strikes at a know
distance is important. The one thing that people using BDC scopes
typically have problems with is that a BDC scope has the reticle in the
second focal plane of the scope. If the reticle was in the first focal
plane of the scope the reticle would look smaller on low powers like 3x
and grow proportionately larger as the power increased to say 9x top
power. The problem is that while the marks on the BDC reticle correspond
accurately to the bullet drop at the know distances 200, 300yds etc.
What happens when you lower the power from the scopes maximum power to
any other lower power is the reticle stays the same size and the field
of view within the scope increases which means that the distance between
these marks on the BDC reticle no longer corresponds to the point where
the bullet will strike. In short BDC reticles only work at the maximum
power of the scope or at a set specific power. At all other powers these
BDC reticles do not accurately represent where the bullet will strike.
Step 4
The center X always remains the same. If you zero at 100
yards and you know that your bullet drops 8 inches at 300 yards you
could forget about the BDC marks and hold the center X 8 inches high -
that works at any power 3x or 9x and should be used at lower powers. If
you zero the center crosshair at 100yds and have the BDC scope at the
maximum power 9X then the first line or circle below the center X should
be the mark you place on the center of the 200 yard target----- the
bullet strike should hit the center. If by some chance you put the scope
on 3x and placed that first mark below the center cross hair on that
200 yard target you would shoot over the top of the target. This is
because as the power of the scope decreases the field of view increases
the angle increase and gets wider. You can experiment with known power
settings and see at a specific power say 3x what that first circle down
corresponds to and make notes because at any set power what the marks
correspond to will be repeatable.
From your short description, it sounds like the Horozontal (the ELEVATION) reticle is canted to the left. If that IS the case then do this;
Sand bag the rifle on what you know is a level and firm surface. The rifle MUST be level itself. You can use a small level to determine this.
Without moving the rifle, look through the scope and determine if indeed the horozontal or ELEVATION reticle is indeed canted. The reticle should be LEVEL in relation to the ground and the rifle itself.
If it still appears to be canted, loosen the set screws of the scope ring caps (Not the scope mounts) and while looking through the scope, gently rotate the barrel of the scope clock wise until the Horozontal reticle appears to be now level. Re-tighten the scope ring caps and look through the scope again to make sure the Reticle is still 'level'.
You must now make sure that your scope is still 'zero'd'.
IF the issue is something other than what I have assumed from your description, please send me a msg. with more detail and I will be able to resolve whatever issue you are having. Include the 'Brand and model', plus the power of it, and the brand/model/cal. of the rifle the scope is mounted on.
i would contact cabelas they have a full line of nikon rifle scopes or look up on line a company called brownells it is a gunsmith supply company they will have what ya need hope this helps ya and good luck
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