Scope not ranging need help??

[hellcat84]

Having issues just looking for some help

To start off, were just two regular guys looking to reach out and we have been doing fine on the closer ranges and progressively moving out to the longer ranges ie start at 200 yards push back to 300 make some changes on the scope push back to 400 ect.

Today we ran into some issues though, generally we move back progressively and on top of that our target sits on fairly level ground with the grass chewed down by gophers so splash is easy to see and we generally correct off of that. Today we switched to a more secluded area as to not annoy neighbours and to gain more range. the new area has tall grass and splash doesn't show up well if at all. trace is visible on most shot but can be missed the odd time.

Our budget is pretty limited and we cant afford a laser range finder or a good spotting scope at the moment. We range our targets with my Nightforce 8-32X56 with the NPR2 reticle and it seems to get us by. generally we range the target with the reticle, get a reading in minutes of angle and then input that information into the range estimator on the knights armament bullet flight ballistic program. from there we get our range, look up our drop on the programs range card for the particular round and put that on the scope. It generally doesn't put us right on target but it gets us close enough to see splash and from there we correct off of splash dialling till we have good elevation. The wind is usually pretty slow where were at but its rarely steady so we generally bracket from the low end to the high end, dial for the average and then estimate our hold if the wind strays from the average or wait for the wind to return.

Generally this process seems to work fairly well but today it went out the window. We fire on a 21X21" steel plate, after hanging our plate we gave it a fresh coat of paint and then headed off on the quad to find a decent shooting position. Once in place I measured the target with the NPR2 reticle to be 2MOA, perfectly framed by my vertical hash marks. inputted into the bullet flight program it spat out a range of 972 yards, that seemed long but we gave it a try and didn't come up anywhere close. From trace I could see that we were inline with the target for windage but wasn't sure of our elevation and couldn't pick up anything for splash in the grass.

I checked to ensure my scope was dialled to 22X or R on the scope to ensure my power was right, I checked my parallax and still got 2MOA. then I reset my ocular focus, set parallax again still 2MOA. we fired a few more rounds and same thing inline with the target but no splash and no idea on elevation. Thinking it was the Ballistic calculator I tried the inches/MOA X 95.5 method and got 1002 yards. I dialled for that range and still got the same effect. At that point we dropped my rifle (22-250) for a .308 hoping to kick up some dirt. The 308 was zeroed for a 400 yard target we had been shooting previously at the old site and had been hitting consistently, my logic was Id spot through my scope while my partner let off with the 30, Id use my reticle to bring him up by viewing his splash and when we got him on target I would add what he had come up to the seven minutes already dialled for the 400 yard zero. We came up 15.5 MOA to get on target, added to the 7 MOA for the original 400 yard zero we had 22.5 MOA. Looking at the bullet flight range card for the .308 load at our temperature and elevation 22.4MOA is our dope for a shot at 760 yards. Then we dropped the .308 and picked up the 300WSM, we put our adjustments for 760 yards on the scope, we misjudged the wind on our first round but our elevation looked good. Holding our wind correction our second round hit dead centre on the plate. At home I pulled up our area on google earth and used the ruler feature to get a distance between where I perceived our shooting position to be vs our target position based on the features I could recognize from the air. Google confirmed 760 yards (actually 763)

what gives??? any ideas, it seems like the scope isn't ranging effectively there is a pretty big difference between 760 yards and 972, about a 200 yards difference. Have we ran into the limits of reticle ranging, that I know the marines mill targets right out to 1000 yards? Any ideas on how I can fix this should I range at a different power level then the one advised by night force. I think we burnt up $20 worth of shells finding our range and were still trying to save our pennies to buy some decent glass for spotting.
:-[

Also how come the bullet flight calculator predicts 972 instead of the 1002 formula I got on paper?? And is the Night force NPR-2 calibrated in true MOA or Shooter MOA maybe that has something to do with it?

 

[Keith Glasscock]

Yes, it should have been 2.6 MOA if your target is exactly 21 inches.

Two things come to mind, were you looking at the target perpendicular to the face? Second, has the zoom power ring come loose? Does it stop at the right positions at max and min power?

Beyond that, how much mirage did you have? It can do funny things!

If there is something wrong with the scope, it should show up at 100 yards. If you look at a grid, the 2 MOA hash marks should span 2.094" at 100 yards.

If it were me, I'd assume that I got fooled.

As for military snipers reticle ranging, there is a reason that they are issued laser range finders.

Hope this helps.

 

[sscoyote]

I'd also confirm the size of your tgt. to see that it is truly 21". That ballistics program's calcs are also wrong. If that 21" tgt is sitting at 760 yds. u should get a "mil-reading" of 1.3-2 MOA units, and that .3 difference should easily be seen with your optics stadia lines.

I always range with my reticles at the optic's highest power. This allows me to interpolate between stadia points to a higher degree of accuracy. So with that reticle at 32x each line to line subtension oughtta' be ~22/32 x 2.094= 1.44 inch per hundred yds.

I would suggest just using a calculator, and establishing a factor for every tgt. size you're gonna be measuring, i.e, for that 21" tgt. it would be 21x 100/1.44=1458 @ 32x. Then just divide 1458 by your "mil-reading" to get your range.

 

[sscoyote]

Actually the ballistics programs rangefinding feature is correct to the level of accuracy of that reticle and the shooter's ability to interpolate the "mil-reading".

The difference between 1002 yds. and 972 yds, using a subtension unit of 2.094 IPHY = only .03 of a unit difference--

1002 yds. is a reading of 1.00
972 yds. is 1.03

So using that large of a subtension relative to that tgt. size 900 yds. or so is right at the limit of it's usefulness.

 

[brian427cobra]

8-32 NSX ranges on 22x, trying to range on any other power setting is your problem.

 

[dieselten]

8-32 NSX ranges on 22x, trying to range on any other power setting is your problem.

He already knows this - it is written in bold in his post.

The NXS can range at any power, as long as you know exactly what the reticle marks subtend - see the post by sscoyote, he is dead on.

It is true that the 2 moa vertical marks equal 2 moa at ONLY 22x, but the power ring is not always accurate. You should graph your reticle from a solid rest at the range to confirm exactly where 22x is and then mark it with a silver sharpie on your magnification ring. Or even better, use sscoyote's advice and range at 32x. No need to graph the reticle (except to give you peace of mind) and just plug in his value's. The higher magnification will yield more precision.

Three other things to be aware of, the rifle/scope have to be rock solid when ranging as the smallest error will throw you way off. The target has to be square to your scope/reticle to yield accurate results. You need to know your correct velocity, BC, & environmentals.

And in my opinion, there is nothing wrong with the NXS 8-32. It is an awesome scope if used correctly.

 

[sscoyote]

Absolutely! If you do intend to use that optic at it's highest power for rangefinding i would definitely measure the subtension at some known distance [usually 100 yds.] to be sure that it subtends that measurement, as power rings are rarely cald. as designated.

I've often thought that the best way to measure the subtension of a reticle though is to "reverse-mil." the subtension from various tgt. sizes at different distances and calculate the avg. reticle subtension. This may be a more accurate way to measure subtensions [though that's just a theory of mine i haven't proven yet].

Nice thing about going to the optic's highest power is that you have a sort of "zero stop" there that ensures you're at the correct power [and consequently subtension] every time.

One other thing that Darrell Holland and i agree about is to subtract one line thickness from your subtension calcs if going off a catalogs specs. as most people [probably] tend to interpolate between line stadia rather than from center of line to center of line. This has worked for me once when using a US Optics spotting scope with a MOA reticle while measuring the dimensions of a 500-yd. tgt. that was almost the exact dimension, though you literally are admittedly "splitting hairs" here with this one...?