tapered scope rails
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stevemc
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Steve,
If you are going to shoot F Class which encompasses all ranges out to 1000yards it is essential to have a tapered rail to mount your scope upon.
This does not give you more elevation ( as I have heard some say ) but it allows you to utilize fully the available elevation built into your scope.
Most top end target scopes have between 50 and 65 moa in elevation. but there are also some about that have up to 90 moa.
If you simply mount a scope with say 65 moa available elevation on a parallel rail ( no taper ) you will find that 300yards will zero about 1/3 to 1/2 way up the scopes travel. You need around 30 moa to reach 1000yards, so what happens is that you run out of available elevation well before 1000yards.
By incorporating a taper of say 20 moa into the scope rail you " pick up " that 20moa on the bottom side of your elevation meaning your 300yard Zero is now 20moa lower than before giving you 20moa more on the top side of your elevation. A scope that has 90moa available may well not need a tapered rail.
Barry
If you are going to shoot F Class which encompasses all ranges out to 1000yards it is essential to have a tapered rail to mount your scope upon.
This does not give you more elevation ( as I have heard some say ) but it allows you to utilize fully the available elevation built into your scope.
Most top end target scopes have between 50 and 65 moa in elevation. but there are also some about that have up to 90 moa.
If you simply mount a scope with say 65 moa available elevation on a parallel rail ( no taper ) you will find that 300yards will zero about 1/3 to 1/2 way up the scopes travel. You need around 30 moa to reach 1000yards, so what happens is that you run out of available elevation well before 1000yards.
By incorporating a taper of say 20 moa into the scope rail you " pick up " that 20moa on the bottom side of your elevation meaning your 300yard Zero is now 20moa lower than before giving you 20moa more on the top side of your elevation. A scope that has 90moa available may well not need a tapered rail.
Barry
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Ken L
- Posts: 473
- Joined: Tue Aug 30, 2005 6:53 am
- Location: Maclean NSW
The best optical preformance occurs when the axis of all the lenses are in a single line this is called Collimation. With a telescopic sight with internal adjustments for elevation and windage this only occurs when the elevation and windage are in the centre of their range of adjustment.
The adjustment for elevation / windage occurs by moving the errector lens off the centre line resulting in a deterioration of optical quality.
The next thing that happens with having a scope adjusted verticaly away from the centre is that the range of adjustment for the horizontal range decreases to a point that with maximum vertical adjustment in place there is no horizontal adjustment available.
Scopes with mountings that are horizontaly miss aligned with the bore line will have reduced vertical adjustments as a converse to the above.
With a scope that has a total of 65 Moa of adjustment range and is set up so the centre line of the scope is parrallel with the bore line (typical with standard scope mounts) the zero for 300 yards is 7.6 Moa off the centre line for a typical 308 cal rifle ( This varies with the height the scope is above the bore line). Then, when you adjust for an elevation for a 1000 y shoot with a typical elevation change of 29.75 Moa.
Adding the 7.6 to the 29.75 and you will find that you have run out of adjustment for elevation and will have no adjustment for windage either.
For a scope with 65 Moa of adjustment on a 308 rifle FS rifle I would have a tapered base with 20 Moa of taper. Thus giving a 300 zero at 27.6 moa off line out of a total of 32.5 Moa. Now at this position you will have a limited amount of windage adjustment but as you dont need much more than 5 moa in the worst conditions you will find this adequate.
From a 300 zero of -27.6 you adjust for a 1000 yard shoot with 29.75 this gives you a 1000y setting of +2.15 moa that gives you the best optical performance when you need it and the near maximum windage as well.
My personal preference these days is to use a set of Burris Signature Zee scope rings as these come with a set of offset inserts that can give off sets from +/- 5 Moa to +/- 20 Moa at 5 Moa intervals just by choosing the correct insert that come with the 30 mm rings or as an extra for the 1 inch rings. The inserts are self aligning and as such the rings dont need lapping as some people are want to do.
As a footnote
I once saw a shoot at Malabar, in the 2000 Macintosh where we needed 8 Moa at 300 but not for long as the targets started breaking away from the frames and coming over the mantlet and the range was abandoned.
The adjustment for elevation / windage occurs by moving the errector lens off the centre line resulting in a deterioration of optical quality.
The next thing that happens with having a scope adjusted verticaly away from the centre is that the range of adjustment for the horizontal range decreases to a point that with maximum vertical adjustment in place there is no horizontal adjustment available.
Scopes with mountings that are horizontaly miss aligned with the bore line will have reduced vertical adjustments as a converse to the above.
With a scope that has a total of 65 Moa of adjustment range and is set up so the centre line of the scope is parrallel with the bore line (typical with standard scope mounts) the zero for 300 yards is 7.6 Moa off the centre line for a typical 308 cal rifle ( This varies with the height the scope is above the bore line). Then, when you adjust for an elevation for a 1000 y shoot with a typical elevation change of 29.75 Moa.
Adding the 7.6 to the 29.75 and you will find that you have run out of adjustment for elevation and will have no adjustment for windage either.
For a scope with 65 Moa of adjustment on a 308 rifle FS rifle I would have a tapered base with 20 Moa of taper. Thus giving a 300 zero at 27.6 moa off line out of a total of 32.5 Moa. Now at this position you will have a limited amount of windage adjustment but as you dont need much more than 5 moa in the worst conditions you will find this adequate.
From a 300 zero of -27.6 you adjust for a 1000 yard shoot with 29.75 this gives you a 1000y setting of +2.15 moa that gives you the best optical performance when you need it and the near maximum windage as well.
My personal preference these days is to use a set of Burris Signature Zee scope rings as these come with a set of offset inserts that can give off sets from +/- 5 Moa to +/- 20 Moa at 5 Moa intervals just by choosing the correct insert that come with the 30 mm rings or as an extra for the 1 inch rings. The inserts are self aligning and as such the rings dont need lapping as some people are want to do.
As a footnote
I once saw a shoot at Malabar, in the 2000 Macintosh where we needed 8 Moa at 300 but not for long as the targets started breaking away from the frames and coming over the mantlet and the range was abandoned.
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Cameron Mc
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Ken L
- Posts: 473
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- Location: Maclean NSW
AlanF wrote:At some stage I investigated the Burris Signature inserts and got the impression they weren't available in 30mm. Is that no longer the case? Are they reasonbly quick to remove from the rail?
Alan
Alan
They have always been available. I have been using them since before the 2002 FCWC because they are relatively easy to remove by removing the 2 screws that clamp the rings to the rail. I did replace the conventional slotted screw with socket headed cap screws.
Look at Sinclair Intn web site. http://www.sinclairintl.com/shooting.html
06-420585
Burris Signature Zee Rings 30mm Matte Extra-High Rings w/Offset Inserts 30mm
Your Price: $ 51.25
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stevemc
- Posts: 11
- Joined: Mon Apr 23, 2007 7:30 pm
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