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Leupold mark 4 knobbs

Discussion in 'Rifle Country' started by chriso, Oct 7, 2008.

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  1. chriso

    chriso Member

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    Anyone own the mark 4 lr/t with m3 knobs? If I understand this correctly the m3 knobs give you 1 MOA adjustments compared to the m1 knobs wich give you 1/4 MOA adjustments wich doesn't allow to make hits on smaller targets because of the inch adjustment increments wich increase over distance? I have been thinking about trading in my mark 4 lr/t m1 for a m3 one. Anyone know why the army prefers to use the m3 knobs instead of m1? The zero stop is what is interesting me in the m3 knobs.
    thanks!
     
  2. chriso

    chriso Member

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    Accidentally double posted this mods please delete!!! sorry everyone!!!
     
  3. MCMXI

    MCMXI Member

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    chriso, I have a Leupold Mark 4 3.5 - 10x M3 with the illumiated TMR reticle. One "click" on the elevation dial is 1MOA and one "click" on the windage dial is 1/2 MOA. The M3 elevation dial is MUCH faster to adjust since one complete revolution of the dial = 60 MOA compared to 15 MOA on the M1 dial.

    :)
     
  4. USSR

    USSR Member

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    chriso,

    With .25MOA elevation adjustments as in the M1 knob, you will use 3 revolutions of the knob to go to 1k with the 7.62x51/.308 Win cartridge. So, when making rapid elevation adjustments, you have to remember what turn of the elevation knob you are on. If you get it wrong, you will be off by 15MOA and cleanly miss your target. No way for this to happen with the M3 knobs, as 0 - 1000 yards are all within the same 1 turn of the knob.

    Don
     
  5. MCMXI

    MCMXI Member

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    USSR, good point!!

    You got me thinking about a couple of things. I took a look at the Sierra ballistic tables for a 168 grain .308 SMK HPBT bullet. The high and the low values are as follows:

    Bullet Path with 100 yard zero and 3400 fps muzzle velocity:

    Yards Drop (in)

    100 > 0.00
    200 > -1.95
    300 > -7.87
    400 > -18.37
    500 > -34.17
    600 > -56.18
    1000 > -232.99


    Bullet Path with 100 yard zero and 2300 fps muzzle velocity:


    Yards Drop (in)

    100 > 0.00
    200 > -6.27
    300 > -21.82
    400 > -48.55
    500 > -88.82
    600 > -145.63
    1000 > -613.66

    The Mark 4 with M3 dials is set up to be zeroed at 100 yards and the 168 grain .308 dial shows 1000 yards right at 43 MOA which is 450.3" (at 1000 yards). So according to the Sierra ballistic tables, I'd need to shoot a 168 grain SMK HPBT with a muzzle velocity of 2600 fps at sea level in "normal" conditions to be on target at the 10 mark on the dial (assuming no crosswind). Actually, the table shows the drop to be 459.6" but you get the idea. So your original point about only having to rotate the dial 3/4 of a turn for a 1000 yard shot is a valid one. Imagine under stressful conditions trying to remember where you left the M1 dial since you'd need to rotate it almost three times for 43 MOA adjustment! There are some indexing marks on the elevation and windage turrets but again, it would be easy to get confused.

    :)
     
  6. USSR

    USSR Member

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    1858,

    Forget about shooting the 168SMK at 1,000 yards. It was designed for 300 meter shooting, and goes transonic and tumbles at 1k. If you intend to shoot to 1k with the .308 Win, then use either the 155gr Lapua Scenar or the 175SMK. Most guys are shooting the 155gr Scenar, as it can be driven to 2950fps.

    Don
     
  7. MCMXI

    MCMXI Member

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    USSR, I don't plan on shooting much over 500 yards and even that's a stretch where I live. My example above was for illustrative purposes to help out chriso (or others) who want to know more about the differences between M1 and M3 dials. But thanks for the tip though .... :)
     
  8. chriso

    chriso Member

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    Yeah i ended up keeping my mark 4 with m1 knobbs it was to much of a hassle and wait and its in the second focal plane. What power does the scope need to be on to use the mills correctly on a second focal plane? my guess is on 3.5?
     
  9. MCMXI

    MCMXI Member

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    chriso, all of the Leupold Mark 4 scopes with variable power need to be on the Maximum magnification to use the range estimating "feature" of the Mil Dot and TMR reticles. That's the only advantage of the FFP scope (as far as I can tell) ... you can estimate range on any magnification.

    :)
     
  10. chriso

    chriso Member

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    Well then that makes me feel better on passing up on the FFP if thats the only difference I thought i was losing out on more than that. Anyone know of a good ballistics computer program? I would also like to print out some Data cards that show drop in inches and MOA adjustments to be made according to drop? stuff like that. So a 1/4 moa adjustment is the same as 100 yards as a couple hundred correct? it still holds the same value in adjustment a quarter of a inch correct?
     
  11. MCMXI

    MCMXI Member

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    chriso, I don't want to bore you but the math is fairly simple.

    1 minute of angle (MOA) = (2 * PI)/21600 radians

    This is because there are 360 degrees in a circle, and each degree contains 60 minutes of angle. So there are 360 * 60 minutes of angle in a circle = 21600.

    Now, for a circle, S = r * theta where S is the length of the part of the circumference between two radial lines of length r separated by an angle theta in radians. 360 degrees is 2*PI radians = 3.14159 * 2 = 6.28318 radians. 6.28318/21600 = 2.9089 x 10^-4. So each MOA is 2.9089 x 10^-4 radians. So at 100 yards, 1MOA = 100 yards*36 in./yd*2.9089 x 10^-4 radians = 1.0472 inches. So 1/4 MOA = .25*1.0472 in. @ 100 yards = 0.2618 inches. So to figure out a 1/4 MOA adjustment at 200 yards you need to do the following.

    1/4 MOA adjustment (@ 200 yards) = 0.25 * 200 yards * 36 in./yd * 2.9089 x 10^-4 radians = 0.5236 inches

    So the short answer is ... NO, a 1/4 MOA adjustment at 100 yards will NOT produce the same results as a 1/4 MOA adjustment at 200 yards. However, the good news is that the relationship is linear so if you know what a 1MOA (or 1/4 MOA) adjustment does at 100 yards, just multiply the effect by 2, 3, 4, 5 etc for 200, 300, 400, 500 yards.

    Here's a question for you ... what would a 1/4 MOA adjustment do at 50 yards? :)

    Note: We've all heard of, seen or used the formula to calculate the circumference of a circle:

    C = 2*PI*R where C is the circumference of the circle. This is the same as S = r * theta. In this special case, S is the circumference, r is the radius of the circle and theta is 360 degrees which is 2*PI radians.

    :)
     
  12. chriso

    chriso Member

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    I will have to re read this and study it How would I do this with quarter moa adjustments haha. I want to be able to do the dope on the fly and not rely on ballistic print outs and what not. Thanks!!!
     
  13. sscoyote

    sscoyote Member

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    Chriso, I would simply run the JBM ballistics program for your load and then simply calculate your dope in mils. There's a window for that right in the program. When i set up a reticle or turrets for holdover and holdoff i put all my dope on a sticker in a Butler Creek scope cap cover (unless it's too complicated) and then it's right there easily referenced with just a simple glance up to it from your shooting position. Here's what an entry would look like in my sticker--

    450-2.4-0.8

    ...obviously range, elevation, then windage reference. This is the most efficient system i could come up with and it has worked for me to intermediate ranges (500-600 yds.), and farther.

    When it comes to rangefinding with the reticle i use the mil-ranging formula for whatever tgt. size i may be after. Here's the formula in it's most basic form inches to yds.--

    tgt. size (") x range of reticle subtension measurement (usually 100 yds.) / reticle subtension (") / quantity of gap tgt. occupies (decimal equivalent) = range (yds.)

    This formula will work with any multi-stadia reticle, not just mil-dot, and in fact is actually better applied with ballistic reticles like Burris Ball. Plex or Leup. Varmint Hunter...IMO.

    EXample--

    For the mil-dot 3.6 inch per hundred yds. and say an "avg." doe antelope (14" back to brisket) that occupies 1.6 mil thru the optic--

    14 x 100 / 3.6 / 1.6 = 240

    ...recognizing that 14x100/3.6 is a constant of 388.89 we can enter that in the calculator's memory to finish the ranging chart like this--

    1.5 = 260
    1.4-280
    1.3-300
    etc, to as far as u feel comfortable with reticle ranging. On "soft" tgts. that i can't judge their dimensions perfectly it ends for me at 400-500 yds.

    Put all this info on a see-thru (Blizzard) style Butler Creek objective cover (it comes apart and u can put some thin cardboard in it with a sticker on it and put it all back together again).

    That's my system and i'm stickin' to it.
     
  14. USSR

    USSR Member

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    chriso,

    The PointBlank exterior ballistics program is a good program for determining drops and such, and you can download it off the internet for free. An easy way of understanding/remembering the amount of correction with 1/4 MOA knobs is: at 100 yards the amount of correction is .25 inches, and for any other yardage, simply multiply the 100 yard correction amount (.25") by the new yardage amount (minus the zeros), i.e. the amount of correction at 400 yards is 4 x .25" = 1.0" of correction per 1/4 MOA adjustment.

    Don
     
  15. chriso

    chriso Member

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    Wow thanks a lot for breaking that down for me buddy!!! I truly appreciate it.
     
  16. chriso

    chriso Member

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    so one more question. With the m3 dials it is already doped out on the knobs but only for a certain type of bullet? what happens when you reload or switch bullets to a higher velocity or heavier grain or what not? are the knobs no good? Im thinking about trading it in for the 1 moa adjustments since it will be scope to learn on fairly long range. well past 600 yards.
     
  17. chriso

    chriso Member

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    Any help im going to do the exchange today any help would be great!!! the zero stop feature seems to be whats winning me over and the fact i wont have to do 3 revolutions to reach a grand but are the knobs useless because they are already dopped out for 168 grain? I plan on developing my own load for this rifle.
     
  18. MCMXI

    MCMXI Member

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    chriso, when I bought my Mark 4 with M3 dials it came with three dials ... one for .223, .308 and .300 Win Mag. It's possible that you could develop a load to closely match the ballistics indicated by the dial but the other choice you have is to develop a load that you like and then pay Leupold $60 to make you a custom BDC dial for THAT load. You'd need to give them information such as bullet diameter, weight, BC, muzzle velocity, typical elevation, typical temperature etc. but from that they would make you a custom dial. I guess my point is, don't worry too much about the dials that come with the scope since you can (and perhaps will) order custom dials from Leupold. Whatever you end up doing, you need to have realistic expectations of what you hope to achieve.

    :)
     
  19. chriso

    chriso Member

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    So you can still dial your own dope it still has marks for 1 moa not just 100,200,300,400 etc. correct? if i know i need 15 MOA of adjustment i can still do my own dope nut just presets correct?
     
  20. MCMXI

    MCMXI Member

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    The M3 dial is marked in 1MOA increments from 0 to 60 so you have up to 60MOA adjustment in one rotation of the dial which means if you know you need to dial in 3, 7, 11, 17, 35, 57MOA or whatever for a given shot you can do it. The 1,2 3,4 .... 9,10 numbers above the MOA increments are there to get you close and give you a quick reference for 100 to 1000 yards but they may be dead-nuts-on if you have Leupold make you a custom dial.

    :)
     
  21. chriso

    chriso Member

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    Sweet i think I will end up exchanging it for that. I thought the adjustments would be to course but seems less confusing better to learn on it seems.
     
  22. chriso

    chriso Member

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    now TMR reticle or mil dot haha Im thinking the TMR looks like it has to much stuff going on. anyone have one and like theirs?
     
  23. chriso

    chriso Member

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    the only thing im concerned with is the 1 MOA adjustments being to course and not being able to hit a decent size target from beyond 600 yards but the zero stop is one thing thats really selling me on it.
     
  24. chriso

    chriso Member

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    Well nevermind I just ended up keeping the m1 model to much of a hassle and wait to get the m3 model. People always refer to the marks that tell you wich revolution you are on but i am unaware of what they are talking about since there is no way to fully dial the knobs down to a stop how do you know what revolution you are on? Also for every 3 little lines and a big line that transfers to 1MOA correct and the little lines are 1/4? or how exactly does this work? I plan on taking the rifle to the range this weekend and walking it out to a good distance and also what are the little allen key slots in the knobs?
     
  25. USSR

    USSR Member

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    There should be a series of lines/marks on the "shaft" that your elevation knob turns on. Note what line is aligned with the bottom of your elevation knob when you are zeroed at 100 yards.


    Exactly.

    Don
     
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