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| Scopes with BDC Reticles for Centerfire Rifles
In the process of researching a new scope selection, I investigated the bullet drop compensation (BDC) reticles I found in scopes that I could afford to purchase. I saw no clear choice for my application. Each manufacturer’s BDC set-ups had advantages and disadvantages. Here is an overview of the different reticles I looked at in alphabetical order with Mil-Dot at the end.
Burris has a Ballistic PlexTM and a Ballistic Mil-DotTM Reticle. They both have similar BDC tics on the lower portion of the reticle but the latter gives you the advantages of Mil-Dots on the upper and horizontal cross-hairs. The Ballistic Mil-DotTM is only offered on higher power scopes, 4-16X and above and 14x is used for the BDC reference. There is no wind compensation integrated with the Burris reticles. The Ballistic PlexTM crosshairs are designed for a 100-yard zero for standard calibers and 200 yards for flatter shooting calibers. The Ballistic Mil-DotTM crosshairs are designed for a 100-yard zero and intended for flat shooting calibers. Burris has a wealth of information on their website but it is hard to find. Try the web address below to download Burris’ BDC files. With a Ballistic PlexTM and 100-yard zero, my .308 would be 2 to 3 inches high beyond 300 yards. Using a 200-yard zero, the ballistic match had even more disparity between this BDC reticle and my .308 rifle’s trajectory.
Bushnell has introduced a BDC reticle called DOATM, Dead On AccurateTM. It is designed to be sighted in at 100 yards with aiming references out to 600 yards and is referenced to the scope’s maximum power setting except for their 4.5-30x scopes which are referenced to 20x. Heat mirage affects could be an issue on hot days with the 2.5-16x and 4.5-30x models. Scope power can only be decreased to tune to your ballistics if your rifle doesn’t shoot as flat as Bushnell’s BDC settings except for the 4.5-30x models. The DOATM reticle is unique in that it provides range estimating by references 18” or 24” wide marks to the ears tips of a whitetail or mule deer, respectfully. Deer in Southern States typically have an ear tip to ear tip spread of around 13 inches. To get the DOA’s range estimating technique to work, you have to be looking at a large deer and get the deer to look in your direction. This isn’t the case for other BDC reticles that provide range estimates based on the height of a deer’s chest cavity. The best application of these spread marks is to reference antler size when the deer is at a known range. The DOATM crosshair reference points use a 1 MOA filled-in circle, 4 times the size of a typical crosshair. There is no wind compensation designed into this scope other than what you can derive from the 9” and 12” reference marks each side of the vertical crosshair. Using a 100-yard zero with my .308 rifle’s trajectory and magnification set at 13.5x for the 2.5-16x scope, the ballistic impacts were on at 200 and 300 yards, an inch high at 400, then much higher at longer ranges by 4 to 10 inches. I found this to be the case with other calibers using boat-tail bullets. The only close ballistic matches I found to this reticle at longer ranges were with flat-based bullets, e.g., Remington’s .243 100gr Core-Lokt and Federal’s.270 130gr Soft Point, .270 150gr Soft Point Round Nose, or .30-06 150gr Soft Points. These are not bullets I would use for long range hunting.
Cabela’s Alaskan Guide Rangefinder BDC scopes have the quickest range estimation to shot down-range that you can find. You don’t have to twist any knobs, take your eyes off your target, or take your rifle off your shoulder to read a dial. The reticle grows and shrinks with magnification, like a European-style scope, so range estimation and BDC work at any magnification setting. This means there is no capability to change magnification to tune the BDC reticle for your rifles performance. The advantage of this set-up is simplicity, e.g., you don’t have to remember to set a magnification to get the correct BDC or worry that it might get bumped off your setting. There are no thick posts to help with low-light situations. The scope is intended for a 200 yard zero with 8 inches of trajectory drop at 300 yards, 23 inches at 400, and 44 inches at 500, typical of .30-06-like performance with boat-tail bullets. The only tuning you can do to match your rifle’s performance is to sight your rifle in slightly high or low at 200 yards to better fit the trajectory drop marks at longer ranges. You can also do simple windage estimation because the centerline circles allow you to project a 9-inch cone either side of the center crosshair at any range. If this BDC reticle closely matches your rifle’s performance, like it did my .308 and the .30-06 factory ammo I checked, it is a good option to consider.
Cabela’s new EXT Reticle was recently introduced on their Pine Ridge and Alpha Series scopes. Unlike Cabela’s Alaskan Guide Rangefinder (above), it is intended to be sighted in at 100 yards. You can also tune the EXT Reticle to your rifles trajectory by lowering magnification if your rifle doesn’t shoot as flat as the EXT Reticle’s ballistic compensation or increasing magnification if your rifle does shoot a flatter trajectory (up to 20%). On their Alpha Series 3-12x scope, the EXT Reticle is referenced to 10x for rifles with .30-06 or similar performance. The directions do not provide any MOA values so I set the scope up in a vise, viewed a point target at about 100 yards to eliminate parallax, and used the elevation turret to click off the distance between BDC marks. The ballistic drop for each BDC reference at 10x measured as follows; 200 yard-tic, 3”/1.5 MOA; 300, 11.3”/3.75; 400, 25”/6.25; and 500 yard, 46”/9.25 MOA. Again, increasing magnification above 10x reduces these values proportionally and reducing the power setting increases these values proportionally. Horizontal BDC crosshairs are 3 MOA wide at 10x except for the wider 300 yard reference which is 8 MOA. This equates to 24 inches wide, 12 inches either side of the crosshair at 300 yards at 10x. For my .308 with the 3-12x scope, the ballistic match was right on at all ranges with the magnification set at 9x. I verified this with shots at 100 and 300 yards. Based on factory data, 9x was also a good power setting for.30-06 ammo with 150 gr boat-tails. My .270 Win with 150 gr Berger VLD bullets had a good ballistic match with the power set at 10.8x. This scope provides an affordable and effective BDC solution.
This can also be used to measure rack size. Using the crosshair on top of the back of a deer, you can get a range estimate using the BDC marks referenced to the bottom of the chest.
Nikon’s BDC reticle uses a series of circles for aim points sized to be 2 inches at 100 yards or 2 MOA, i.e., 4 inches at 200 yards, 6 inches at 300 yards, etc. There is no wind compensation integrated with their BDC reticle. The reticle is designed for a 100-yard zero for standard calibers and 200 yards for flatter shooting calibers. The top and bottom of the aiming circles can be used for intermediate ranges. With a 100 yard zero, if you rifle shoots flatter than the reticle’s trajectory compensation, then you can either compensate for point of impact being high or sight in for 200 yards and turn down the magnification to tune the scope to your rifle’s trajectory curve. As an example with my .308, the downrange impacts would be 1 to 2½ inches high with 100 yard zero (this would be considered adequate for most hunting situations). I could sight in for 200 yards and get a good trajectory match with a 3-9x scope set on 7.6x magnification. If I want to shoot at 9x with a 200-yard zero, I would have to define specific ranges for each circle. Example, the first 1st circle would be on target at 285 yards, the 2nd circle would be on at 375 yards, etc.
Leupold has a capable set-up with range estimation and wind compensation available on their VX-III scopes. Range estimation is accomplished by adjusting magnification until the animal’s chest fills the crosshairs up to the tip of the top thick post then reading the range in hundreds of yards on the other side of the power ring. Range estimation assumes an 18-inch chest depth. Wind compensation on their Boone & CrockettTM Reticle is for a 10 mph crosswind component. Depending on the performance of your rifle, zero ranges are designed to be 200 or 300 yards with some calibers requiring a lower power setting for accurate trajectory matching which is marked by a small triangle at 8x on their 3.5-10x and 11.2x on their 4.5-14x scopes. You can fine tune the BDC reticle to your rifles performance by adjusting the magnification to provide proportionally more or less bullet drop. In the case of my .308 and their 3.5-10x scope with a 200 yard zero, the BDC reticle would be tuned with the scope set on 8.8 magnification. Specific reticle details regarding calipers, bullet velocities, and MOA of reticle markings can be downloaded from the Leupold’s website, file name “Leupold Ballistics Reticle Supplement” (see link below). The Leupold VX-III scopes have less range of magnification than other manufactures, e.g., 3.5-10x vs 3-12x, 4.5-14x vs 4-16x. Leupold’s 4.5-14x is nice at the higher power settings but if you read the specification, their 4.5 is really a 5x magnification (4.9x).
Weaver is entering the market with a BDC reticle (Fall 2009). Their EBX reticle is offered on their Super SlamTM scopes which have a 5:1 magnification capability, e.g., 2-10x, 3-15x, and 4-20x. The EBX provides wind compensation for a 10 mph crosswind component. You should be able to fine tune the EBX reticle to your rifles performance by adjusting the magnification to provide proportionally more bullet drop if your rifle doesn’t shoot as flat as Weaver’s BDC. Preliminary plans are to reference the EBX reticle at full power. If your rifle shoots flatter you will have to use different ranges, e.g., .270 Win 110gr bullets would be 200 yards, 330, 455, and 570 yards (use link below for your specific caliber). In the case of my .308 and their 3-15x scope with a 200 yard zero, the BDC reticle would be tuned with the scope set on 13.5x magnification. If Weaver goes into production with the EBX reticle referenced to full power, then there is the possibility heat mirage affects could be an issue on hot days with the 3-15x and 4-20x models. If Weaver references the EBX reticle on these two models to a power setting less than 15x and 20x, then these models will have the capability to be tuned to for flatter shooting rifles.
The Mil-Dot reticle is a standard for almost every manufacturer and has a center crosshair with dots spaced one milli-radian apart, the equivalent of 3.6 MOA or 3.6 inches at 100 yards. The dots are typically 0.2 mils in diameter. A Mil-Dot scope can do it all; range estimation, BDC, and windage. However, it takes some calculation and memorization of what range each mil-dot represents. Some shooters affix a ballistic reference card to their rifle stock. Range estimates for a deer or antelope sized target, assuming an 18-inch chest, are 5 mils for a deer at 100 yards, 2.5 mils for 200 yards, 1.7 for 300, 1.25 for 400, and 1.0 mil for 500 yards. Military sniper scopes of the recent past have been 10x which has become a standard reference for many variable power Mil-Dot scopes but not all. Thus, check to make sure what magnification power the Mil-Dot reticle is reference to. Some manufacturers will use the scopes maximum power. You can search the web and find abundant information on how to use a Mil-Dot scope.
It turns out that a Mil-Dot reticle can be an effective BDC reticule if your muzzle velocity is around 3000 fps and your bullet's BC is near 0.5. The link below takes you to a thread with an excel spreadsheet that can you can use to tune a mil-dot reticle to your firearm out to and beyond 500 yards along with lessons learned trying to shoot at these distances.
Bullet Drop Compensation w/ Mil-Dot Reticles: an Alternative
There is an aspect of BDC reticles that I didn’t realize before I bought my Mil-Dot scope. You can usually reduce magnification to provide increase trajectory drop, but if your rifle shoots flatter, there is typically not an option to increase magnification to reduce trajectory drop because most of the BDC settings are already designed for a scope’s highest power settings. Your option is to sight in at a longer range like 200 or 300 yards and or learn to compensate for your bullets impacts being high at each range tic. As it turns out, a Mil-Dot reticle is best for my application because my .270 Winchester load, using Barnes’ 110 gr TTSX copper banded bullets with their higher velocity, shoots flatter than the BDC reticles I considered. The only BDC scope that would have come close to matching my rifles performance was the Burris Ballistic Mil-DotTM but at the longer ranges my impacts were still high. If you rifle is a flat shooter, I would suggest doing some homework to see how well the BDC scope you intend on buying can be matched to your rifle’s performance. This may also be important with standard calibers because each BDC reticle is different. The link below takes you to a thread that includes an Excel worksheet that allows you to compare trajectories for the different BDC reticles and determine what magnification setting best tunes to your rifle’s performance. If you fine tune a BDC to your rifle’s performance by reducing the scopes magnification, you will most likely need to mark that power setting in some manner as a reference. The examples of BDC tuning to my .308 in the paragraphs above were done referencing ballistic trajectory tables and the fore mentioned Excel spreadsheet. In all cases, verification of your rifle’s performance needs to be accomplished with shots downrange. Remember, there is no substitute for practice!!!
Scopes with BDC Reticles for Centerfire Rifles
Posted by slimjim on Wednesday, May 07, 2014 (00:57:55) (5621 reads) [ Administration ]
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