mntnflyr4fun
Member
2nd focal plane (SFP) BDC scopes,with a “busy” sight picture for extended range shooting (300yds+) seems counter-intuitive to the idea of increasing accuracy at distance and quickly getting cross hairs on target and a bullet down range. If not a busy sight picture, you have your mind on twisting knobs counting clicks or looking at tiny engraved markings on your elevation knob hoping to get the scope set before the game disappears behind some brush across the canyon before you are ready to get back to the job of shooting.
Throw in low light, the reduced eyesight that comes with aging eyeballs on top of the adrenaline rush of finding a browsing bull 500yds across a canyon and it’s a disaster waiting to happen..
I sold my last BDC scope and bought another Zeiss Conquest with a std. Z-plex and began looking into other methods of gaining long range accuracy without doing the old “hold over and hope” type of shooting that comes with a conventional sight-in practice of setting up for a fixed 200 or 300 yard zero or grandpa’s “1 ½” high at a hunerd” is all you’ll ever need idea.
Using the Sierra Infinity program (others can get you to the same place, I am just used to using InfinityV6) I locked onto the concept of using the MPBR (Maximum Point Blank Range) calculation to define my sight in range to provide a minimum of two fast acquisition sight points with a 3rd to extend the range if need be. The idea being a maximum range that the bullet will remain inside a defined kill zone size. Fast and accurate was what I wanted and the MPBR method seems to fit like a glove.
Using this method a defined kill zone size is designated based on the size of the game you are planning to hunt. In my case, I was building a 30-06 load for elk hunting out to 500yds and I chose a kill zone size of 15” for Roosevelt Elk in the Oregon Coast Range.
Running the MPBR calculation resulted in a MPBR of 399yds for my load of a 200gr. Nosler Accubond at 2688fps, 24” bbl.
To achieve this I sight my gun in for a 337yd. zero which equates to sighting in 5.6” high at 100yds.
The result is that I can hold dead on (center mass) from 0 – 399 yds and hit inside the 15” dia. kill zone. No hold over etc., if the rangefinder says ts under 400yds., center up and send the bullet downrange and it will not be higher or lower than 7.5” from where I have the crosshairs. Dead Elk.
There is a 2nd easy to find/acquire hold point to extend the MPBR approach, and that is the top of the back (TOB). In my case, I assumed the TOB to bottom of chest at 30” so with my aim point out to 400yds being pretty much center mass, there is an additional 7.5” to the top of the back.
Referencing once again the data generated during the MPBR calculation and following the bullet path to the range where the bullet has dropped to -23.5” (15” kill zone +7.5” more to the TOB) gives an extended range of 487 yards. Being able to quickly make the decision of the range being over 400, but under 488yds with my rangefinder, I can quickly decide on a center mass or TOB hold and know that I can put a round in the kill zone if I can do my part.
Lastly, a simple tweak to extend the range even further with very limited “Kentucky windage”.
At the extreme limits of the ranges discussed above will produce hits at the bottom of the 15” kill zone. So in fact if the range exceeds the 2nd range point of 487yds where your bullet will hit at the bottom of the kill zone, you really still have a 3rd hold over point that is up to 15” above the back to still put one in the top of the kill zone.
In my case, this range turns out to be (23.5”+15”=38.5” total drop) puts my extreme range right at 550yds. Only now the bullet will be entering the kill zone at the top of the 15” circle instead of the bottom….
I feel this gives me a credible 3 point 550yd ranging system that is quicker than a massive range table taped to my stock, or a difficult to see jumble of lines/dots/knob markings etc. where I can easily make a selection mistake or take to long to setup. I expect to be able to reduce my kill zone size during load development as a true 500yds is as long as I plan to shoot, but 15" is a good starting point for now.
This same method can be easily used for any game you choose to target with the same load. It is a simple matter of running the MPBR calculation on a larger or smaller kill zone, following the range data to come up with a TOB hold and a max holdover point based on drop, making the zero range adjustment to the scope and head off to chase moose, deer or antelope etc.
With the money saved on an expensive BDC scope you can buy a top of the line standard scope setup with Duplex reticle to make it a slam dunk to see where your crosshairs are.
My last observation would be that this technique would work even better with a first focal plane (FFP) scope as the crosshairs would grow in size along with the target at higher magnifications opening up more possibilities to get the crosshairs right on the money. Alas, FFP scopes seem for some reason to be made of gold dust or something as I have yet to run across a comparable scope to my Leupold VX3 or Zeiss Conquest with the FFP arrangement that I can afford.
Anybody that can poke holes in this I am listening…….
Throw in low light, the reduced eyesight that comes with aging eyeballs on top of the adrenaline rush of finding a browsing bull 500yds across a canyon and it’s a disaster waiting to happen..
I sold my last BDC scope and bought another Zeiss Conquest with a std. Z-plex and began looking into other methods of gaining long range accuracy without doing the old “hold over and hope” type of shooting that comes with a conventional sight-in practice of setting up for a fixed 200 or 300 yard zero or grandpa’s “1 ½” high at a hunerd” is all you’ll ever need idea.
Using the Sierra Infinity program (others can get you to the same place, I am just used to using InfinityV6) I locked onto the concept of using the MPBR (Maximum Point Blank Range) calculation to define my sight in range to provide a minimum of two fast acquisition sight points with a 3rd to extend the range if need be. The idea being a maximum range that the bullet will remain inside a defined kill zone size. Fast and accurate was what I wanted and the MPBR method seems to fit like a glove.
Using this method a defined kill zone size is designated based on the size of the game you are planning to hunt. In my case, I was building a 30-06 load for elk hunting out to 500yds and I chose a kill zone size of 15” for Roosevelt Elk in the Oregon Coast Range.
Running the MPBR calculation resulted in a MPBR of 399yds for my load of a 200gr. Nosler Accubond at 2688fps, 24” bbl.
To achieve this I sight my gun in for a 337yd. zero which equates to sighting in 5.6” high at 100yds.
The result is that I can hold dead on (center mass) from 0 – 399 yds and hit inside the 15” dia. kill zone. No hold over etc., if the rangefinder says ts under 400yds., center up and send the bullet downrange and it will not be higher or lower than 7.5” from where I have the crosshairs. Dead Elk.
There is a 2nd easy to find/acquire hold point to extend the MPBR approach, and that is the top of the back (TOB). In my case, I assumed the TOB to bottom of chest at 30” so with my aim point out to 400yds being pretty much center mass, there is an additional 7.5” to the top of the back.
Referencing once again the data generated during the MPBR calculation and following the bullet path to the range where the bullet has dropped to -23.5” (15” kill zone +7.5” more to the TOB) gives an extended range of 487 yards. Being able to quickly make the decision of the range being over 400, but under 488yds with my rangefinder, I can quickly decide on a center mass or TOB hold and know that I can put a round in the kill zone if I can do my part.
Lastly, a simple tweak to extend the range even further with very limited “Kentucky windage”.
At the extreme limits of the ranges discussed above will produce hits at the bottom of the 15” kill zone. So in fact if the range exceeds the 2nd range point of 487yds where your bullet will hit at the bottom of the kill zone, you really still have a 3rd hold over point that is up to 15” above the back to still put one in the top of the kill zone.
In my case, this range turns out to be (23.5”+15”=38.5” total drop) puts my extreme range right at 550yds. Only now the bullet will be entering the kill zone at the top of the 15” circle instead of the bottom….
I feel this gives me a credible 3 point 550yd ranging system that is quicker than a massive range table taped to my stock, or a difficult to see jumble of lines/dots/knob markings etc. where I can easily make a selection mistake or take to long to setup. I expect to be able to reduce my kill zone size during load development as a true 500yds is as long as I plan to shoot, but 15" is a good starting point for now.
This same method can be easily used for any game you choose to target with the same load. It is a simple matter of running the MPBR calculation on a larger or smaller kill zone, following the range data to come up with a TOB hold and a max holdover point based on drop, making the zero range adjustment to the scope and head off to chase moose, deer or antelope etc.
With the money saved on an expensive BDC scope you can buy a top of the line standard scope setup with Duplex reticle to make it a slam dunk to see where your crosshairs are.
My last observation would be that this technique would work even better with a first focal plane (FFP) scope as the crosshairs would grow in size along with the target at higher magnifications opening up more possibilities to get the crosshairs right on the money. Alas, FFP scopes seem for some reason to be made of gold dust or something as I have yet to run across a comparable scope to my Leupold VX3 or Zeiss Conquest with the FFP arrangement that I can afford.
Anybody that can poke holes in this I am listening…….