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Leupold BDC on Mark 4

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rod haydel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rod haydel Quote  Post ReplyReply Direct Link To This Post Topic: Leupold BDC on Mark 4
    Posted: May/22/2008 at 16:39
I need help. I just installed a Leupold Mark 4 in a 2.5 x 8 that has BDC dials for a 7.62 168 grn. bullet. According to ballistics I can find a 168 grn bullet drop appox 4.7 inches at 200 yards and 14.8 at 300 yards if it is dead on at 100. The BDC dial shows 2 inches of compensation at 200 and 5 inches at 300. Something is not adding up here. Do I need to sight in differently? The girl at Leupold Tech assistance did not seem to know what she was talking about and just suggested I have them make some custom dials for me at my expense. Any one have any ideas here? Thanks
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supertool73 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: May/22/2008 at 16:56
It is probably in MOA not inches.  2 MOA at 200 yards is about 4 inches.  5 moa at 300 yards is about 15 inches.
I don't think those are BDC dials, they are just MOA dials. 

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Kickboxer View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: May/22/2008 at 17:12
Every BDC I've owned I have had to shoot in to confirm BDC settings and in some cases annotate differences. Just 168gr bullet is not enough info to go on. You need to know powder load, seating depth, etc. If you are reloading, you can probably build a load that will perform to your BDC. Leupold should have a chart that shows what particular ammo configuration they used, or you should be able to call and ask them.
I quit using Leupold several years ago, so am not familiar with your exact optic. However, it is common to have to shoot to confirm BDC settings. And then, the Leupold custom shop WILL dial it in for you, for a fee. I have heard they do excellent work... depends on your $$ pain level.
However, there are Masters in this forum who may have experience with your particular scope. My $.02 is shoot it in and see.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Urimaginaryfrnd Quote  Post ReplyReply Direct Link To This Post Posted: May/22/2008 at 18:13
LEU60220 Leupold%202.5-8x36%20Mark%204%20MR/T%2030mm%20Riflescope%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20 Leupold 2.5-8x36 Mark 4 MR/T 30mm Riflescope
  • Matte
  • Illuminated Tactical Milling Reticle
  • 30mm
  • M1 Target Knobs
  • Index Matched Lens System
SWFA: $1,079.95
More%20Info...

LEU60160 Leupold%202.5-8x36%20Mark%204%20MR/T%2030mm%20Riflescope%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20 Leupold 2.5-8x36 Mark 4 MR/T 30mm Riflescope
  • Matte
  • Mil-Dot
  • 30mm
  • M2 Target Knobs
  • Index Matched Lens System
  • Free Leupold Flip Up Covers w/ Purchase
SWFA: $949.95
More%20Info...
These scopes have about 90 moa of internal adjustment windage and elevation usually about half above and half below unless you use a plus moa base from Badger Ordnance.
example 168 gr Sierra matchking balistic coeffecient  at 2650 ft per sec is .462
http://www.black-hills.com/rfactorynew.htm the .308 BH is a 168 SMK at 2650 fps.
From what I understand so far you have the M2 (short) knobs that have built in balistic compensation. M2 knobs are 1/2 minute of angle per click where the M1 knobs are 1/4 minute of angle per click. At 100 yds one minute of angle is essentially one inch at two hundred yards one minute of angle is essentially 2 inches and so on one minute of angle 300 yds is 3 inches, 400 yds one minute of angle is 4 inches.   So if  you sight in at 100 yds ZERO and  you are using 1/2 moa per click here is your chart, just remember that that 1/2 inch at a hundred is not 1/2 inch at 400 it is 1/2 moa or 2 inches think of it as parts of a circle the farther out you go the bigger the piece of the pie. If you want custom knobs for different weight bullets order from Kenton Ind. the link is above.
 
Advanced Ballistics Calculator -   
 
Range
yds
Path
in
ComeUp
clicks
Velocity
fps
Energy
ft/lbs
Momentum
lb ft/s
ToF
sec
Windage
in
Windage
clicks
Optimal
Game Wgt
Muzzle -1.5 Infinity 2650 2620 63.60 0.000 0.0 NaN 788
25 -0.6 5 2602 2526 62.45 0.029 0.0 0 746
50 -0.1 0 2555 2435 61.32 0.058 0.2 1 706
75 0.1 0 2508 2347 60.20 0.087 0.4 1 668
100 0.0 0 2462 2261 59.09 0.118 0.8 1 632
125 -0.5 1 2416 2178 57.99 0.148 1.2 2 597
150 -1.4 2 2371 2097 56.91 0.180 1.7 2 564
175 -2.6 3 2327 2019 55.84 0.212 2.4 3 533
200 -4.2 4 2283 1944 54.78 0.244

"Always do the right thing, just because it is the right thing to do".
Bobby Paul Doherty
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Urimaginaryfrnd View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Urimaginaryfrnd Quote  Post ReplyReply Direct Link To This Post Posted: May/22/2008 at 18:23
If it was M1 knobs with 1/4 moa clicks this would be the chart:
Range
yds
Path
in
ComeUp
clicks
Velocity
fps
Energy
ft/lbs
Momentum
lb ft/s
ToF
sec
Windage
in
Windage
clicks
Optimal
Game Wgt
Muzzle -1.5 Infinity 2650 2620 63.60 0.000 0.0 NaN 788
25 -0.6 10 2602 2526 62.45 0.029 0.0 1 746
50 -0.1 1 2555 2435 61.32 0.058 0.2 1 706
75 0.1 -1 2508 2347 60.20 0.087 0.4 2 668
100 0.0 0 2462 2261 59.09 0.118 0.8 3 632
125 -0.5 1 2416 2178 57.99 0.148 1.2 4 597
150 -1.4 3 2371 2097 56.91 0.180 1.7 4 564
175 -2.6 6 2327 2019 55.84 0.212 2.4 5 533
200 -4.2 8 2283 1944 54.78 0.244 3.1 6 503
225 -6.3 11 2239 1870 53.74 0.277 4.0 7 475
250 -8.8 13 2196 1799 52.70 0.311 4.9 8 448
275 -11.8 16 2153 1729 51.67 0.346 6.0 8 423
300 -15.2 19 2111 1662 50.65 0.381 7.3 9 398
325 -19.1 22 2069 1596 49.65 0.417 8.6 10 375
350 -23.5 26 2027 1533 48.65 0.453 10.1 11 353
375 -28.4 29 1986 1472 47.67 0.491 11.7 12 332
400 -33.9 32 1946 1412 46.70 0.529 13.4 13 312
425 -40.0 36 1906 1355 45.74 0.568 15.3 14 293
450 -46.7 40 1866 1299 44.79 0.608 17.3 15 275
475 -54.0 43 1828 1246 43.86 0.648 19.5 16 258
500 -61.9 47 1789 1194 42.94 0.690 21.8 17 243
525 -70.5 51 1752 1145 42.04 0.732 24.3 18 228
550 -79.9 55 1715 1097 41.15 0.776 26.9 19 213
575 -89.9 60 1678 1050 40.27 0.820 29.7 20 200
600 -100.8 64 1642 1006 39.41 0.865 32.7 21 187
625 -112.4 69 1607 963 38.57 0.911 35.8 22 176
650

"Always do the right thing, just because it is the right thing to do".
Bobby Paul Doherty
Texas Ranger
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rod haydel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rod haydel Quote  Post ReplyReply Direct Link To This Post Posted: May/22/2008 at 19:31
Thanks for everyone's help!
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