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I have a trijicon mil dot 2.5-10 Power scope and am wondering about hold over from a 100 yard zero. I know mil dots can be used for a range finding apparatus at 10 power on this optic but am wondering if anybody has any input for a consistant hold over without doping my scope seeing it doesn't have external turrets, although it has target style adjustments under dust caps. I am shooting 123gr rounds right now but plan on reloading my own 100 or so gr. rounds quite soon. Any pointers would be greatly appreciated!!! Thanks!
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Not difficult to use mildots for holdovers, but there are a variables (such as exact bullet with ballistic coefficient, muzzle velocity, altitude, etc) that you would need to plug into a ballistic calculator in order to get accurate information.
I use the trajectory calculator on the JBM Ballistics website, and simply indicate that I want the drop data in mils. Sounds like your scope's reticle is in the second focal plane, which means that not only is ranging accurate at highest power, but also the holdovers will only be applicable at the same setting.
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BD:Originally posted by neandrakall View Post
Just curious. What does 'doping the scope' mean? Do you mean putting elevation on your scope?
Some things to consider.
Your initial zero will be different between what ever 123 grain loads you are using and what ever 100 grain loads. So, you will have to adjust your optic when switching loads and this will be both elevation and windage. It is best to find this initial zero and the difference at 200 yards and not 100 yards. 100 yards is too short a distance to come to good conclusions on zero differences and accuracy. In fact, I would say this is important enough that you should sacrifice a day to drive to a range that is at least 200 yards measured distance with 300 yards being better.
Next thing is to get a chronograph and chronograph each of your loads so you can run them through a ballistic computer and find elevations at various distances so you can figure out how many mil hold over you need for certain distances.
Can't say that I have heard of someone starting at 100 with mil holds. Generally they start at 300 but the use of such holds is marginal when you hit 600, even with a TMR reticule that has 1/2 mil ticks. Also, it gets pretty hard to use holds over three mils and harder still to use holds that involve both elevation and windage when either gets over two mils.
Another thing. All small arms ammunition holds pretty much the same ordinate to 300. Generally five to eight inches of ordinate. Zero at 300 and if you are using kill zones of about 20 inches or more, a center hold will get you from your barrel to 300. Use the mils for distances past 300 but you will lose precision very fast once you hit 600 and or if you start going into mil holds of over two mils.
LR1955Comment
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Could you elaborate on the quoted lines above? -ThanksOriginally posted by LR1955 View PostDrifterComment
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Drifter:Originally posted by Drifter View Post
Sure. Given a 10X M-3 or M-2 optic on a M-24 or M-110, an average trained Army Sniper, and issued M-118 SB or LR. Using a 300 meter elevation and hold overs, hit probabilities are reduced significantly when the shooter has to use any combination of two or more mils of either elevation or windage. In other words he is using more than about a two mil hold from 300 for elevation and particularly when he must use such a hold for both elevation and windage. Hold overs do OK to 500 from a 300 zero but past 500, other factors take over, making it better to try and estimate a good range and index elevation (I do not recommend indexing windage except for unique environmental conditions).
Other factors that tend to play a much more critical role past 500. Danger space reduces immensely, making range estimation more critical and making it more necessary to be accurate in a mil hold to the 1/10th of a mil. Inability to dope wind and convert to mils fast enough combined with trying to track a moving target, thick reticule pattern found in the M-3 / 2 scopes and most civilian optics that use a mil reticule, 10X starts losing its performance at 600 and beyond, difficulty in a person being able to maintain a hold when that hold is far from the cross hair as the cross hair tends to be the point where the eye will shift to in order to figure out if it is holding '2.7 mils' or elevation while trying to hold '1.8 mils' of right wind for example.
LR55Comment
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Thanks for the additional info. I understand your points.
I use a 200-yard zero, and while I usually dial up with the elevation turret for target shooting out to 600 yards, I sometimes use a combination of dialing up and holdover. For example, my drop at 600 is 4.3 mils for a particular load. As practice for potential hunting applications where as a quick shot needs to be taken (or at least in less time compared to informal bench shooting), and potentially in low light when dialing up 43 clicks wouldn't be ideal, I'll dial up 3 clicks and hold on the 4-mil line. Works very effectively with the right scope (using a FFP reticle such as Gen II XR, NF MLR2.0, USO GAP, etc at somewhere around 15x to 17x, with 0.1-mil clicks).
Admittedly, I don't have to deal with much wind since I usually do my informal shooting on a wooded path (although I do seem to get ~0.1 mil of spin drift at 600 yards). Thus, your points seem valid if attempting to hold for both elevation and windage (especially if the turrets do not match reticle). Thanks again for sharing your insight.DrifterComment
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Drifter:Originally posted by Drifter View Post
Not a problem. We are talking about different sets of conditions and different types of equipment. We also use a 500 meter elevation and holds which are OK to about 700 on meter high targets. If a guy has the time, it is more precise for him to put the elevation on his optic when he exceeds 600 as he then has a diagonal stadia with mil dots from which he can see his wind holds more precisely. There are some advantages to BDC turrets and the M-2 has both meters and minutes on its elevation so it is more precise but not necessarily more user friendly. You really have to look to make sure you are using distance verses minutes. And seeing those numbers is impossible in low light conditions.
What you are doing is nothing uncommon. Just finding the easiest solution for your conditions.
One thing that I have wondered about from time to time is that guys don't seem to trust their elevation dial. If your optics have 15 minutes per full revolution for example, and it is a quarter minute scope, that 42 clicks turns into three full revolutions then back three clicks. Many times I have seen guys count clicks instead of seeing where they are on the dial and just turning it full rotations. I wonder why sometimes.
LR1955Comment
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Thanks Guys!! Good input. So if I zero my scope at 300 yards, will I have to hold under for say a 100 or 150 yard shot? And once I begin reloading I plan on setting my rifle up for one specific load. Weather it is 100gr or a bit larger. Maybe you have some good input on that as well?? As soon as winter breaks I will be at the range using this info that has been given to me.Comment
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Zero yardage is what works best for you and your particular application, and / or what you're accustomed to.Originally posted by neandrakall View Post
In my case, my shooting background stems primarily from hunting. For many years, I used the common medium game cartridges (.270, 30-06, etc) with common hunting scopes (3-9x with duplex reticle) sighted in for 200 yards, which enabled shots out to ~250 yards without much thought using a center hold. And though both me and my equipment have evolved, that same 200-yard zero still works in most of my hunting applications. It's what works best for me, but not necessarily for everyone.DrifterComment
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I can see two different disciplines with different zeros described here.
For hunting, most agree that a 200yd zero provides the best point blank zero with high power, center-fire rifle cartridges, since you keep the trajectory within a narrow imaginary tube for the longest distance.
For shooting human silhouettes or steel at further distances, you might use another zero if you are relying on holds, or better yet, just dial as LR1955 stated.
I prefer to dial either way, and like scopes that have rugged target knobs with solid, repeatable gears. If I don't have time to dial, I know that I will get out to 300yds no problem, and will hold on the head/neck area often on a man-size silhouette. For a medium game target with a 10" or smaller kill zone, I want to be as precise as possible, especially as the distance comes into play.
.270 Winchester is hard to beat when it comes to a flat-shooter within 500yds, and I grew up loving that cartridge/rifle, with my dad's Pre-64 Model 70 Featherweight. Shooting water jugs was always a pleasure since it made them explode on contact.Comment
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ND:Originally posted by neandrakall View Post
Depends on the kill zone size. We are talking what hunters call a Point Blank Zero and the military calls a Battle Sight Zero. What ever elevation setting you select depends on; (1), whether or not you care about using such a zero; (2) the size of your kill zone in height; (3) what you believe is your average engagement range.
I would use a 115, 120, or 123 grain bullet with the Grendel as you can get about the best velocity while maintaining magazine length. And, in hunting terms when using a cartridge that does not produce high velocities, I would rather go with kinetic energy as a major factor than hoping a bullet will open up.
LR1955Comment
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