There is a lot of misunderstanding about BDC (Bullet Drop Compensation) scopes. It seems shooters either value them highly or dismiss them out of hand.
The fact is that these scopes can be highly effective. However, to get the best out of them, you really do need to carry out some initial homework. But, this will be time well spent when it comes to the expected end results.
Let’s look at one manufacturer’s take on this and answer the question, How to use Nikon BDC scopes in the most effective way?
What is BDC, and How is it Used in Scopes?
BDC in scope terms refers to “Bullet Drop Compensator,” and that is exactly what these scopes are designed to do; compensate for bullet drop over varying distances. They include a BDC reticle that has crosshairs with sub-markings on the downward crosshair. These extra markings indicate different distances.
Manufacturers pre-set scope reticles with the crosshair commonly zeroed at 100 yards. From there, BDC reticles have aim points placed directly below the central crosshair. Generally, these are in 100 yard increments for centerfire scopes and 50 yards for rimfire scopes.
For example…
Let’s look at a scope that is zeroed at the most common distance of 100 yards. When looking at a target that appears to be 400 yards away, you can use the mentioned BDC sub-markings. Simply line up the target with the 400 yard sub-marking, and it should give accurate shot placement at that distance.
On standard scopes, the reticle is represented by lines or a crosshair for measuring scoping distance. BDC scopes use a reticle pattern that is designed to predict where a shot will land. It does this by guesstimating how much a bullet is expected to drop at a certain distance.
A big selling point of BDC scopes is their ability to give shooters rapid adjustment. Meaning that because of the sub-distance markings, you should know exactly where to aim. It also allows you to place your ‘dot’ on different distances without the need to worry about elevation turret adjustment.
However, as would be expected, there are limitations and expectations, these include…
Average trajectory/Popular cartridges
It is very important to understand that you are not buying into a “magic bullet.” There are things you need to get right, and there is homework to be done. One other thing that needs taking on board is that real world shooting does not conform to convenient and exact distances.
But, before getting into these points, let’s have a look at Nikon’s take on what their BDC scope models have to offer.
They state that their BDC reticle has been designed to compensate for the trajectory of your firearm or crossbow. This is regardless of the particular BDC reticle you go for.
This is because the scope’s etched circle positions are based on the average trajectory of some of the more popular cartridges and projectiles available. They also go further by stating that the reticle is ballistic information based. This means it may or may not give the same results for each shooter.
So, here are some of the variables that can come into play and need taking into account:
Actual Velocity
This relates to information that ammo manufacturers give regarding muzzle velocity. It might or might not match the velocity produced by your firearm or crossbow. Those who want to get the best velocity results should use a chronograph. This will determine the actual muzzle velocity of their firearm or crossbow.
There is also the consideration of how ammo is sourced. Either from a retailer or hand-loading/reloading (making your own ammo with brand new brass or repurposing used brass).
Temperature / Humidity / Altitude / Barometric Pressure
These four conditions can individually and in tandem affect accuracy.
Condition of your firearm and its inherent accuracy
Some firearms are far more accurate than others. Mass-produced weapons are certainly not known for their ‘spot on’ accuracy. Even different batches of the same weapon can result in different results.
You then have those who build their own weapons. Again, depending on experience in build and quality of parts used, it is only natural that accuracy will vary.
Your scopes mounting system
Whether you are using a BDC or any kind of scope, this really is a major accuracy factor! The most common cause of accuracy issues is an incorrectly mounted/wrongly aligned scope.
Check and then double check that your scope to the centerline of the weapon bore is true. You can be just a few millimeters out with mounting, and this will result in inaccurate shot placement. Reasons for this include such things as barrel cant.
How To Use Nikon BDC Scope in Your Favor?
Nikon quite rightly points out things that could cause accuracy issues while using their BDC scopes. However, they also give a few tips on how to get the most from them.
Let’s start with the need to fully understand the parameters they have based the reticle system on. Once these are understood, you can then start to optimize your setup. The bottom line is that you need to be exact when it comes to truly matching the ballistics data used with your scope.
Some examples of Nikon’s recommendations:
Polymer-tipped bullets are highly recommended for long-distance shooting. This is because they are more aerodynamic and offer a flatter trajectory.
As for their ‘Standard BDC Reticle,’ this has been designed to be used with either of the following cartridge categories:
Standard Velocity
Cartridges with approx. 2,800 fps (feet per second) muzzle velocity. For this, it is recommended that your weapon is zeroed at 100 yards using standard velocity cartridges. Once complete, it should provide BDC at 200, 300, 400, and 500 yards using the respective ballistic circles.
Magnum Velocity
Cartridges with approx. 3,000 fps muzzle velocity. It is recommended that your weapon is zeroed at 200 yards using magnum velocity cartridges. Once complete, it should provide BDC at 300, 400, 500, and 600 yards using the respective ballistic circles.
For cartridges that do not fall into the above categories, there are online resources available. These will help match your exact cartridge to the reticle and provide exact yardages per circle. Studying these and using recommended cartridges will give unparalleled ballistic data when it comes to longer range shooting.
Here Are Two Magnification References You Should Always Bear in Mind:
First, your center crosshair will not change with magnification. This is because it is placed in the optical center of the scope.
Second, similar to other manufacturers, all Nikon BDC reticles are designed to be used on the highest magnification. This means that when changing power (magnification) levels, the position of circles in relation to your target changes. When referring to charts with associated diagrams, these will often show distances listed at the highest magnification (unless stated differently).
It should also be noted that additional information is freely supplied by other manufacturers, firearms websites, and blogs. This data provides accurate information that will match whatever load you are shooting against the relevant BDC reticle. These charts can also be printed for future reference and when out shooting.
Factor in “real world” Shooting Conditions
This brings us to the truth of “real world” shooting. It is regularly drilled into us that targets only present themselves at distances in 100 yard multiples. If only!
Prey you hunt will often be seen and acquired at a variety of distances such as 260, 147, 385 yards, or whatever? Likewise, those into 3-gun competitions should not expect targets to be exactly 400 yards on the button.
The take-away from the above comments probably makes you think that BDC scopes predicting shot impact at 100 yard intervals are not really that good. This is not so! What you are getting is a useful indicator in terms of bullet trajectory that will give accurate shooting over extended ranges.
Time for a field trip…
Now is the time for you to put some work in at the range. This is to evaluate the weapon you are using and the load you are firing. You can do this by shooting at targets that start close and move out and at distances you know the scope’s reticle has been calibrated for.
Note your load and your point of impact at these different distances. If shots are walking off paper too quickly, this tells you there is a reticle vs. bullet trajectory mismatch. To counter this, you can move your targets back/forward at just 10 yard intervals until POA (Point Of Aim) coincides with POI (Point Of Impact) at each distance.
With patience…
You will find rounds striking the target center on a regular basis. That is the distance you can then associate any particular aiming point with. No, it won’t be a nice round multiple ‘100 yard’ figure. However, it will give you an accurate reading from where you can make those all-important finer hold-off adjustments from!
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Final Thoughts
The Nikon BDC scopes that are still available represent a good option for shooters. As for other BDC scopes, it is clear they have a growing future. This is seen by the fact that all major scope manufacturers produce models.
As mentioned, they are not simply a magic bullet option. Please do not expect to point your weapon, move your BDC circle over the target, shoot and score a direct hit. As with any scope, range homework needs to be done. This is through checking ballistic charts and finding POA/POI (Point Of Aim/Point Of Impact) at different distances.
Your weapon needs to be in good condition, and your ammo or projectiles need to fit the profiles given. Just as importantly, your BDC Scope MUST be mounted correctly. If you need any guidance on this, take a look at my informative article on How to Mount a Scope.
Gather all of this together, and when you do head out shooting, there will be a deserved reward. You will find that a BDC scope is a very useful shooting tool indeed!
Happy and safe shooting.
