From the drop chart, I see that at my altitude, this load will drop 22.6 MOA at 1000 yards. Can my scope elevation compensate 22.6 MOA ? The scope I have is a Lynx LX3 with 100 MOA total elevation adjustment, which divided by 2 gives me 50 MOA adjustment capability.

The total elevation adjustment for a scope is bisected by the zero point. There is half of the total travel available to drop the reticle, and half to raise the reticle, which is why only half the total elevation travel can be used to increase the shooting distance.

Yes, the scope is good enough to get those bullets on target at 1000 yards.

From the drop chart, I see that at my altitude, this load will drop 56.7 MOA at one mile using the Berger calulator, and 58.4 MOA using the JBM calculator. Can my scope elevation compensate 58.4 MOA ?

The scope I have is a Lynx LX3 with 100 MOA total elevation adjustment, which divided by 2 gives me 50 MOA adjustment capability.

No, the scope alone is not good enough to get those bullets on target at one mile.

I do have a 20 MOA rail on the rifle, so I have 12 MOA to spare at one mile, using 155 grain Nosler Custom Comps in my 308 Norma.

You can add MOA to your elevation travel with a MOA rail. Common sizes are 10 and 20, some manufacturers produce a 40, and you could have a custom rail made in any inclination. This adds the relevant MOA directly to the vertical adjustment capability of the scope.

Adding a 10MOA rail to the 58 MOA scenario, means there is technically sufficient adjustment in the scope for 1600 yards, but prectically you should have a few more MOA to play with in case the ballistic calculator does not entirely match your actual trajectory, so instead of a 10 MOA rail, use a 20 MOA rail with a 100 MOA scope.

Update the calculator with the next highest bullet BC and expected velocity for that bullet, and redo the calculation. Repeat till the required elevation is less than what is available. You may encounter a trade-off, where the higher BC bullet at a lower velocity has a bigger MOA drop than a higher velocity bullet with a lower BC, and this will be more obvious as the range decreases. For very long range, BC usually trumps velocity. For your case, compare the result of several calculations with different bullets and velocities, to see what is optimal for your application.

If there is no heavier bullet available for the caliber, and the required elevation is beyond the range of your scope, you could

• try find a scope with a bigger adjustment range

• fit the appropriate MOA rail

failing which you need to consider a bigger gun.

Don't use unrealistic BC numbers as input. Browse the bullet listing from the various suppliers online, and become familiar with the range of BC values for the caliber. Make notes as you go, keeping track of what the BC value is per bullet weight per manufacturer. This will be very useful for your calculations.

The next higher BC bullet after Nosler 155 grain Custom Comp is either a Berger 168 grain target bullet with a 0.507 BC, or a Nosler Custom Comp in 175 grains with a BC of 0.505.

From the reloading data, I can expect around 2850 fps for a 175 grain bullet, and 2950 for a 168 grain bullet. Using those velocity numbers with the corresponding bullet weight and BC figure, we get 62.4 MOA required elevation for a 168 grain .507 BC bullet, and 67.8 MOA for a 175 grain .505 BC bullet.

Observe the apparent contradiction : a higher BC bullet showing more drop at one mile than a lower BC bullet.

A 155 grain Nosler CC has a mediocre BC of 0.45 . The Berger 168 grain drops 4 MOA more at one mile, with a 0.507 BC. This is the trade-off mentioned in the opening paragraph - a higher velocity with a lower BC may beat the higher BC with the lower velocity, at a particular range.

Remember the altitude number in the calculator. I calculated with my current elevation, what happens if I go shoot at sea level ? The calculator says the elevation required then increases to 82 MOA, which is beyond the range of this scope and a 20 MOA rail.

This example is still not at maximum bullet weight for the caliber. Moving to heaviest bullet, with the highest BC, Nosler have a competition bullet of 220 grains that I can use. It has a BC of 0.69. The load data suggests a velocity of 2650 fps, which from the ballistic calculator shows 69.5 MOA adjustment required at one mile. This is still more of a drop that the 155 Nosler CC, but the bigger bullet can carry to 2 miles, while the smaller cannot.

Bullet choice should co-incide with actual availability, in that the bullet you choose should be readily available. It's no use if the bullet remains theoretical on paper.

The calculated required MOA of 69.5 is too close to the limit to rely on. The calculator is not precise, and very seldom conforms exactly to measurements. The calculation can be used a guideline, but remains to be proven with actual shooting. The calculation shows I can use my .308 Norma for one mile shots with 220 grain Nosler Custom Comps, but possibly not at sea level. At this point, you need to bring in the twist rate.

Once you have identified a candidate bullet, it's BC and estimated velocity, you have to check what barrel twist that bullet will need. A 220 grain .308 caliber bullet needs a 1 in 10 barrel twist. My barrel is a 1 in 14, so there is no practical way for me to use this rifle for one mile shoots with 220 grain bullets, in spite of the ballistic calculator showing I can reach the distance within my elevation adjustment range, because the trajectory calculated by the calculator does not factor the barrel twist at all.

If you're shopping for a rifle, you need to make that one of the purchase criteria, or the rifle will not be able to shoot the required bullet with any accuracy.

No. The barrel twist is too slow for the heavy bullet, and the light bullet doesn't have the BC to get to two miles.

If the barrel was a 1 in 10 twist, I could use the 220 grain Nosler Custom Comp to get to 2 miles, but I would need a 300 MOA scope adjustment to get on target. These are available from various manufacturers as 300 MOA adjustable rails, or add-on scope prisms.

Now you can go ahead and look for / order your rifle in the chosen caliber, with the required barrel twist.

As important as having the right scope, the right load for the right velocity and bullet BC, is having the platform set up correctly :

• bedding must be done properly

• action screw torque must be correct

• scope rail torque must be correct

• scope ring torque must be correct

• the scope reticle must be aligned vertical in relation to the bore

• the rifle must pass the Tall Target Test

• aim for single digit shot to shot velocity variation with your reloads

Then you are ready for long range competition shooting.

If the caliber you chose is marginal, and the available bullet BC's are not suitable for your application, you need a bigger gun.

You can go bigger in two ways - by powder capacity or by caliber. The more powder you can get into a case the more the velocity will be. Generally, not always, bigger calibers can make use of bigger bullets with higher BC. If the BC of the bigger caliber is not appreciably higher, the velocity will be, and so extend the practical reach of the cartridge.

No caliber is accurate by virtue of it's designation. Accuracy is a product of platform reliability and consistent ammunition, not caliber.