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Old November 16, 2019, 04:07 PM   #1
ncrypt
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MK1-MOA reticle - what am I doing wrong

Caveat up front - I've never used a reticle like this before so it is new to me.

I put a 3x9x40 Nikon P Tactical scope with MK1-MOA reticle on my 7mm Magnum rifle to try shooting at a little longer distances. I know it's a low end scope but the reviews seem good and the price was right for me.

I zero'ed it at 50 yards. No problems here.

I was using my hand loads that consistently give my around 3000 fps with 150 grain Nosler partition. I used my chronograph today to be sure.

The problem comes in when I went to use the hash marks to shoot at a target 250 yards away. I used the Spot On site that Nikon provides to help you to determine bullet impact at each hash. According to the site, the first mark is 246 yards. So I went to 246 yards (checked with my Sig Range Finder) and took a shot.

The bullet was 8 inches low and this was using the first mark, which is WAY off. Using the Shooters Calculator I should only be about 5 inches low at 250 yards. Given that each mark is 2 (edit - mistakenly had 1) MOA, its seems that the Nikon site had it right as well.

BTW - this is a second focal plane scope so I had it zoomed at 9x for all shots.

Does anyone have any idea what I'm doing wrong? I'm baffled.

I only took two shots and both shots hit around 8 inches low.

Thanks for your help

Last edited by ncrypt; November 19, 2019 at 05:59 AM.
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Old November 16, 2019, 07:12 PM   #2
Bartholomew Roberts
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How did you have the rifle rested? Did you notice any shadows or darkness on the edges of the scope? What is the height over bore of the scope and does that match the ballistic calculator you used?

I don’t think two shots is going to provide enough data to diagnose the problem; but we can guess.
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Old November 16, 2019, 07:17 PM   #3
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You have a 3-9X40 scope. No one makes a 3X9X40 scope.

Most scopes with that type reticle recommend a zero of either 100 for non magnum rifles or 200 yards for magnums. 50 yards is pretty close and while you THINK it is zeroed at 50 yards you may not be. Zeroing at 100 yards will show small errors that may not be evident at only 50 yards.

Nikon has the BC for that bullet wrong on their app, it should be .387, not .465, but those alone don't explain that much error.

Most of my scopes have a similar reticle, including at least one Nikon identical to that. I don't worry about trying to get things EXACT. I zero at 100 yards and the other hash marks are close enough to 200, 300, 400, and 500. In fact when I run the numbers for your load zeroed at 100 the hash marks correlate to 216, 319, 406, and 524.

The difference between 200 yards and 216 yards isn't going to cause you to miss any game animal at those ranges. Nor will the difference between 500 and 524. Every rifle, and every load will be slightly different, but closer than most people think. Unless you're rifle is capable of 1" groups at 500 yards there is no need to get the EXACT range where each hash mark is located.

Just for fun I ran the numbers for my 308 shooting 150 gr Ballistic tips. With a 100 yard zero each hash mark correlates to 207, 307, 392, and 509. This is why a flat shooting rifle is no longer an advantage. With the same hold my 308 will still make hits out to 500 just as easily as a 7 mag.

I think you're trying to over complicate things. Zero the rifle at 100, go shoot it and see where it is hitting at longer ranges. I'd forget about the app. Even if you can get the exact ranges the hash marks correlate to you're highly unlikely to find a target at exactly that range. Deer don't just stop at exactly 200, 300, 400, and 500 yards and wait for you to shoot. They will be at odd ranges such as 173, 224, 377, etc. You'll still have to learn how to hold over/under by 2-4" at extended ranges. But that is a lot easier than holding over 2-4 FEET with a standard reticle.
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Old November 16, 2019, 08:43 PM   #4
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Quote:
Nikon has the BC for that bullet wrong on their app, it should be .387, not .465,
Nosler doesn't think so.
https://shop.nosler.com/nosler-bulle...llet-50ct.html
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Old November 17, 2019, 06:03 AM   #5
ncrypt
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Thanks for the info guys.

I had the rifle on a rest. There were no shadows and my scope height is 1.5 inches above bore.

Sighting in at 100 makes sense with this type of reticle. I'm used to trying to maximize my old hunting scope with two POI's.

I realize I can just figure out where it's hitting and go with it, but thought I must be doing something wrong with such a drastic low POI. I compensated with 5" (first hash) holdover and still hit 8 inches low. Seems impossible.

I appreciate any other thoughts.

I hope to shoot again tomorrow.
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Old November 17, 2019, 07:46 AM   #6
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50 yards or 100 doesn't matter, but the further out you zero the more your groups will tell you. Getting all the data possible will improve any ballistic app. What was your SD and ES of the rounds fired? Did you get all your atmospherics inputted properly as well? The SpotOn app will get you close but it us only as good as the data put in.
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Old November 17, 2019, 08:42 AM   #7
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So i plugged your info into Srelok, they are confirming the 0.456 G1 BC.
Sighted at 50 yards, for my atmospherics of Central PA.
At 200 yards the bullseye should be at the bottom of the horizontal hash marks.
If you use the full verticle hashmark shows 265 yards.
I'm guessing your chrono is off.
Try zeroing at 100 yards. Then go for a target 600 yards, if available to you and true your velocities.

Still your 8" low is WAY off!
Check your mount & ring torque. You did use a torque wrench, and not just gorilla tight, right?
Wwhile your at it check your action screws.
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Old November 18, 2019, 08:33 AM   #8
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Nikon’s BDC reticle requires you to take range estimates at max power. The hash mark on the reticle represent a elevation that changes with magnification and Nikons SpotOn app accounts for this change. So if you tell the app that the scope is set at 4 and you change it to 9 you will miss your target. A setting of 9 will require higher aim point than a setting of any of the lower values. The app will give you this info but I can’t recall where it’s located. I hope this is not too vague or disjointed or confusing etc......
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Old November 18, 2019, 08:57 AM   #9
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Oldday,
The OP is hitting low. Any reduction in power seting on the scope would have them hitting higher.
Something else is off here. But without me being there, i just can't put my finger on it.

About the only thing i can really think of is that for that bullet, out of that gun, at that velocity, the barrel harmonics are on the downward swing.
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Old November 18, 2019, 10:22 AM   #10
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"...zeroed it at 50 yards..." That'd do it. So would using 150's for long range shooting out of a hunting rifle.
A 150 is a light bullet for a 7mm Mag. A 150 at ~ 3100 FPS and sighted in at 50 yards drops about 4.5" at 250. And a 150 at 3100 FPS has about 19 ft-lbs of recoil energy. It could be the recoil that causing you grief. Magnums tend to do that.
"...Sighting in at 100 makes sense with this type of reticle..." The reticle makes no difference.
"...Using the Shooters Calculator..." Don't rely on a computer program to compute ballistics. There are far too many variables.
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Old November 18, 2019, 10:33 AM   #11
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You're reading the reticle wrong. You're confusing the "B" measurement with the "D".



"D" is the distance between hash marks which is 2 MOA. "B" is the length of the smaller hash marks which is 1 MOA. "I" is 30 MOA so you have "G" 10 MOA distance between the longer has marks which are "E" that are 4 MOA in length.

Using your data at sea level I get a 249 yard first hash mark not 246, and I doubt you're shooting at sea level. I live at 4000' ASL and that gives me a 252 yard first hash mark with a 3000 fps MV and 50 yd zero. However, that doesn't explain why you're shooting 8" low from the first hash mark at 246 yds.

I seriously doubt anything is wrong with your scope mounts or action screws since it sounds like both shots were close, but it never hurts to check them. I think std7mag hit the problem though, your chronograph is reading incorrectly being off nearly 200-300 fps. SpotOn has a muzzle velocity calculator you can use to check against your Chrony, if you're close to 3000 fps you should have a -3.0" drop from a 100 yard zero at 200 yards or a 0.5" rise from a 50 yard zero at 100 yards.

So either rezero at 100 yds and shoot 200, or shoot a 100 yd target from your 50 yd zero and measure the change and plug the info into the app. This should get you close to your true MV. This will also tell you if it's a chrony issue or not.
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Old November 18, 2019, 12:25 PM   #12
Don Fischer
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All cartridges have two point's of impact, which I think you mean the bullet pass's the line of sight. I limit my big game shooting to 300 yds max. Actually have only done that one time, normally my shots come in 200 yds or less! I did get a scope for fooling with long range target's, Nikon 4 1/2-14 w/adjustable turret's. Has those foolish dot's in it and I completely ignore them. When I got the load I wanted I zeroed the rifle in for max point blank range at an 8" target. Max was somewhere around 280yds, the bullet hit 4" low. To adjust out to 500 yds I ran it through a program in my chronograph using the MPBR I have in it. Told me how many clicks to adjust out to 500 yds and I simply adjusted the scope and went for it. Shot at all the ranges I got printed out and it was scary accurate! No need for those dot's and hash marks, you see something even at 300yds and you likely have more than enough time to adjust the scope. With those dot's and hash marks I don't know what to tell you, I think they are little more than a gadget to improve sales! As I understand it, seem's you have to contact the scope maker to find out what each dot will do with the load you have. Obviously the dot's distances change with the bullet and or cartridge. if your really sure you want to use them. Zero the load and then through trial and error find out the zero point for each dot! Boy that would be time consuming and probably use up a lot of ammo. Otherwise, chronograph your load, run it through a ballistics's program and plot the bullet path to where you want to go. Then adjust the scope and shoot against what you have. For me it's much simpler!
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Old November 18, 2019, 01:48 PM   #13
Bart B.
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Quote:
Originally Posted by T. O'Heir View Post
"...Using the Shooters Calculator..." Don't rely on a computer program to compute ballistics. There are far too many variables.
Why not if it has inputs for the variables then gives good data proved by actual shooting at different ranges?

I've used Sierra bullets software to calculate sight settings at 300, 600, 800 and 1000 yards based on chronograph data and 100 yard zeros for different 30 caliber bullets leaving at different velocities. Down range zeros were calculated to within half MOA of what actual zeros were.

If NASA can calculate trajectories to land a rover on Mars or fly one around Pluto, calculating a bullet's trajectory across several hundred yards on earth is easy. So is determining your metallic sight exact click value; scope exact click value ain't easy to get.

Last edited by Bart B.; November 18, 2019 at 06:46 PM.
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Old November 19, 2019, 05:49 AM   #14
ncrypt
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Thanks for all the great suggestions and information.

I shot again yesterday and figured out a couple things.

1 - When I moved out to 250 yards (see OP), I had to use a plastic table with my rifle rest. Well not paying attention to my weight on the table (I recorded it) caused the significant drop. I'm guessing I pulled the shot during the trigger press.

2 - Using a more stable platform. I did learn that the first hash mark is dead on at 200, NOT 246 with a 50 yrd zero.

I can't explain why I'm getting 4 inches of drop at 200 when it should be 2 inches, but at least I know where it's hitting.

It could be the chronograph, but based on my load data I should be around 3000 fps. I shot some left over factory loads which were also consistent with velocity on the box. I couldnt get the app to work on my new phone so I dont have the SD. It would have to be 200 or more fps less to shoot 4 inches low at 200.

Maybe the mark on the scope is not 2 moa.

I'll keep working on it . I'll check bullet drop without using the marks.

Thanks

Last edited by ncrypt; November 19, 2019 at 06:34 AM.
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Old November 19, 2019, 06:06 PM   #15
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Quote:
Originally Posted by ncrypt
1 - When I moved out to 250 yards (see OP), I had to use a plastic table with my rifle rest. Well not paying attention to my weight on the table (I recorded it) caused the significant drop. I'm guessing I pulled the shot during the trigger press.

2 - Using a more stable platform. I did learn that the first hash mark is dead on at 200, NOT 246 with a 50 yrd zero.
Pulling shots wouldn't make you shoot low. Loading a bipod heavily or sling tension can cause your POI to be off from POA. So a little info about how you were shooting off the bench, and what kind of 7mm RM you have would be helpful especially what kind of stock is on it.

Second if your hash mark is dead on at 200 yards now from a 50 yard zero that would indicate a problem still with your chronograph. 2700 fps at the muzzle at sea level calibrates your first hash mark to 201 yards. You really need to verify your chronograph is actually giving the correct measurements.
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