Trouble with leupold CDS setup

Discussion in 'Long Range Scopes and Other Optics' started by fireworks, Sep 18, 2013.

  1. fireworks

    fireworks Member

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    I recently recieved my scope back from leupold aand gave it a go last night. I was not impressed. While sighting in at 100 i took the opportunity to verify my load. It is spot on and quite stable on the velocity with only a 40 FPS variation in six rounds for a mean FPS just 17 over what was ordered ( I've been tweeking it with crimpimg) and 3 of the 6 verified zero and fit in a dime. The scope was ordered at a mean velocity of 2920 and yestredays mean over 5 was 2937. Again, only a 40 fps deviation over the six. Yet this thing gets expotentially higher the further out you go. At 700 yards its over a foot high. Called leupold and they scratched their heads and want me to click count each 100 yd increment and build me a new dial. Thats alot of work with the open in 10 days. I read somewhere if you zero at 350 (1/2 the turret ) and set the dial back at 350 it will "wash" out the variation in a manner you can live with for hunting. Thoughts?
     
  2. stomp442

    stomp442 Well-Known Member

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    What bullet are you using? Did you provide a G1 BC or G7 to luepold? And did you provide an actual bc or a published one? If using a published G1 BC this could explain why you are off at extended ranges. Just thinking out loud.
     
  3. fireworks

    fireworks Member

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    Bullets are berger VLD 150 grain 270. Provided published g1 co efficient but this bullet has been around long enough if the published and actual BC is different shouldnt leupold know better?
     
  4. stomp442

    stomp442 Well-Known Member

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    They probably do but they are going to use the data given them by the customer.
     
  5. fireworks

    fireworks Member

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    How would one determine/locate the TRUE BC?
     
  6. stomp442

    stomp442 Well-Known Member

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    The problem with the G1 is that it is very velocity dependant. The b.c. you are getting at the muzzle may be .531 but that is not the b.c. you are getting at 700 yards. When calculating an accurate ballistic chart you really should use the G7 b.c. with a bullet matching the G7 standard projectile shape. Also an accurate scope height is needed and needs to be factored into the ballistic solution. The only other thing I can think of is updraft of wind current affecting the bullet impact. Different atmospheric conditions can change things too. Lots of variables come into play from day to day.
     
  7. cummins cowboy

    cummins cowboy Well-Known Member

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    so did you chronograph your load?? this is easy to figure out, go to JBM calculations and run the numbers for your load. this HAS to be done using a chronograph. next compare what JBM says to the numbers on the custom turret they made for you. do they match?? I also recommend doing a 200 yard zero on your rifle and the turret. don't just do a well I should be 1.5" high at 200 for a 200 yard zero, zero the rifle AT 200 yards. I like doing a 200 yard zero because it has some distance and drop to the bullet and gets well beyond issues with sight height and all that

    I have had great luck with the CDS setup. its great out to about 600 yards then varying conditions become a factor that can't be ignored.
     
  8. lloydsmale

    lloydsmale Well-Known Member

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    i tried mine out the other night. Its a 4x12 vx2 on my 300 ultra. Its sighted in at 200 yards load is a 165 tsx barnes at 3325. I never verified it on paper except to make sure it was still zeroed at 200 with the dial at its stop on 200. It was so i went hunting shot one deer at 250 and didnt change a thing as i didnt feel i needed too. Second deer was shot at 380 and i put the dial on 380 and shot. Bullet hit a bit high (about 3 inches) but at that range it could have been me as i was shooting over the hood of my pickup off a jacket. But bottom line is it got me minute of boileroom. Havent had the chance to check it any further yet.
     
  9. theo98

    theo98 Well-Known Member

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    Jerry,

    When I went to order my custom CDS dial for my VX-6, I wanted to ensure it exactly matched my custom rifle & load equipment performance. As per above, Leupold verified exact accuracy "if" I took the time to shoot my elevation adjustments from 200 to 600 yds. We started out with the Brian Litz G7 ballistic data program, but had to reduce the elevation adjustments while shooting at 300-400-500-600 yards. The program was calling for too much height adjustment compared to my real world elevation settings to hit the X-ring target.

    I then submitted all my data, especially the Exact DOPE (data on personal equipment) ballistic settings for the given ranges. My new custom CDS elevation dial exactly replicates (using same eq., environmental conditions) the MOA settings I had to dial in.

    Extra work...yes! However, If I had turned in the general ballistic data requested (10 data point items), I too would be shooting high as the fine tuning in JBM calculator was close (good starting point), but not exact!

    Ted
     
  10. LongRangeBangin

    LongRangeBangin Well-Known Member

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    I have 2 cds dials, on a 300 mag and my sons 308. Both are spot on as far out as the dial goes. I set both these scopes up for a 200 yards zero.
     
  11. Kurt

    Kurt Well-Known Member

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    why I would never use a cds as conditions are always changing
     
  12. theo98

    theo98 Well-Known Member

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    Yes Kirk, they sure do. However, where I hunt I'll have at most an 80deg. max temp differential between my CDS ballistic data and the severest cold.

    With my .30-06 loads (Barnes 168gr TSX-BT Triple Shock - Hodgdon 4350 56g - Lapua Brass), a 10 degree hunt is an additional 1 MOA drop at 600 yds (6"). Dialing in 4 clicks pass the 600yd CDS dial will quickly get the cross hairs POI back on target. Closer in (the norm should be 200 to 400yds), the adjustments will be much less picky. gun)

    Now, all of this is theoretical...the Biggest factor hindering accuracy will be ME! :D
     
  13. Kurt

    Kurt Well-Known Member

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  14. theo98

    theo98 Well-Known Member

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    I felt as you do about this dial. I didn't buy my VX-6 to get this benefit feature, but since it came with it, I'll make the best use of its capability! My responses were just to support the OP's questions.

    Elevation, and for sure ammo changes, will make the dial obsolete! For me, both are "locked in" to the same hunting area and load usage, so my gimmick CDS dial should perform as expected. At the range, it's been deadly between 200-600yds. We'll see what happens in the real world this coming season!

    Safe Hunting!!