Help with BDC reticle

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patncor

New member
I just bought a weaver kaspa 3-12x44 scope and it has a TBX
Tactical Ballistic X ret. which was designed for a 55gr 223 bullet drop points at 2,3,4,5 & 600 yds. My question is what will be the easiest way to calculate yardages for a 150gr 308 bullet? I have left msg's at weavers tech line but no replys so far.
 
Do you by any chance have either an android phone or an iPad. If so you should look at ballistic app Strelok. You can see you reticle and yardages for all powers if you plug in the numbers for your bullet. I used 150 gr .447 bc bullet and 2550 fps with your reticle and a 100 yd zero. 12 power first line 187 yds, second line 275, third 368, 4th 475, bottom of narrow post 550, top of thick post 575. I can load your numbers and email results to you straight from app if you pm me your load data. Can also email reticle shot with hold offs.
 
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Thanks for your offer its kind of funny because I've been looking at that App for a few days. As I reply here my daughter is downloading it to her ipad right now for me. I was pretty stoked when I saw the TBX on the reticle list but the BC will be good for my other scopes as well.
 
Several years ago Weaver stopped publishing their reticle subtensions in their catalogs--something i didn't like much. Be willing to bet you the vertcial subtensions are the same as all the other reticles that are set up for their 223 specs.
 
Originally Posted By: RRPP223Do you by any chance have either an android phone or an iPad. If so you should look at ballistic app Strelok. You can see you reticle and yardages for all powers if you plug in the numbers for your bullet. I used 150 gr .447 bc bullet and 2550 fps with your reticle and a 100 yd zero. 12 power first line 187 yds, second line 275, third 368, 4th 475, bottom of narrow post 550, top of thick post 575. I can load your numbers and email results to you straight from app if you pm me your load data. Can also email reticle shot with hold offs.

Great Program.
 
I did something to make it a little more simple to remember when hunting. I took the ballistic calculators drop in inches and plotted them on a piece of poster board. Top line was 0, went down 3" and drew a line, 4.5" down from there and drew a line, etc, etc, etc. I put the target at my zero yardage (100 yards) and adjusted the zoom on the reticle until the drop lines one the target up as closely as possible to the reticle. I then marked my scope so that this zoom (mine ended up around 7x) would always be 100 yard drop increments on my sight. I realized this issue with BDC when I first purchased my scope and realized the crosshairs and reticle were on the second focal plane, and the drops did not increase proportionally with zoom.

In my mind, this makes sense. Does that seem correct to you more seasoned shooters?
 
That is a pretty good way to do it. In fact a number of the optics companies use the same system in their ballistic programs--Nikon Spot-On, Zeiss, Gerald Perry's Exbal, and some others, based on the ~inversely proportional nature of reticle subtension measurement vs. magnification. Another way to do it is to shoot your dope at longer distances that should come close to matching the stadia points according to the ballistic programs. Then convert the true drop at each range to MOA. Then go back and mark the 100 yd. target and adjust the power until the reticle comes close as possible to all the avg. bullet drop MOA's.
 
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