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Nightforce NP-R2 Integration

 
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Old 01-15-2003, 02:55 PM
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Join Date: Jun 2001
Location: Palmer, Alaska
Posts: 2,539
Nightforce NP-R2 Integration

This is a COPY of a recent exchange on another thread that many might find helpfull in understanding the principle of the R2 integration as S1 explains...

I copied it to a Word document for later reference myself. I titled it "Nightforce" so a quick search later would be an easy recomendation to others that might be interested. [img]images/icons/smile.gif[/img]

Any other caliber at the same velocity and BC should be easily integrated too. This will save a lengthy explanation AGAIN on the same subject... This outlines it very well I thought. Just the relevant posts were copied.
Enjoy. [img]images/icons/wink.gif[/img]


S1
Member
Member # 963 posted 12-03-2002 10:07 PM

Brent
Tell me what your rifle is
Cartridge?
Barrell length?
.....What is supposed stop the bullet?
..What range and altitude do you typically hunt or shoot at? TWIST RATE?
Brent
Member
Member # 85 posted 12-03-2002 10:38 PM

.....What is supposed stop the bullet?
Not sure what you mean by that?

300 Ultra Mag
25.94" barrel (boltface to muzzle)
10 twist
100' to 200' ASL, sometimes we hunt at 2000' and 3000" areas too.
100-1500 Yard range is Max.
--------------------
Brent

Posts: 562 | From: Palmer, Alaska | Registered: Jun 2001 | IP: Logged


S1
Member
Member # 963 posted 12-03-2002 11:00 PM

Brent

Great rifle for R2 trajectory intergration!
...Many possibilities but I need to Know if you are punching paper or killing what?

The R2 is designed to be zeroed at 600 yds, and to shoot a bullet with a b.c. between .495 and .535 at a velocity of 3340 to 3420 with typical lead bullets. Each tic mark above the main cross hair then matches an even 100 yd. increment for very fast target elevation adjustment. This system was actually made for boatails with powdered tungsten & tin cores and works precisely to 1000 yds. Lead bullets work with the reticle very well out to 700 yds. at sea level.
Tell me what the bullet is supposed to hit and I can tell you more but in a very specific way.

Brent
Member
Member # 85 posted 12-03-2002 11:37 PM

I thought that's what you meant, but wasn't certain.
The bullet is punching paper at present, and 36 inches of moose later next year if all works out as planned.
The 220gr SMK is the bullet I'll use if it shoots well, I'll test it later this week and next. I'm using a 180 Nosler BT and 180 Scirocco at present, they're loaded for accuracy at 3200 fps even.
You have my interest peaked now.
--------------------
Brent

Posts: 562 | From: Palmer, Alaska | Registered: Jun 2001 | IP: Logged


S1
Member
Member # 963 posted 12-04-2002 12:07 AM

Brent
The 220 smk is too heavy to integrate with the reticle below 6,000 ft. altitude, and your short (relative) barrel makes the 180 with the highest b.c. the smart place to start.

We have to find you a load with the 180 that will get you between 3360 and 3400. Most barrels like to tune up in this range somewhere and you can save some time by starting with RL-25 and Fed 210s. One of the beautiful things about this system of zeroing at 600 yds. and using hold under rather than hold over, is that mild cant error is reduced for shots less than 600 yards without the shooter conciously doing anything. Its all in the Geometry of the barrel (bore line) being under the optical center of the scope, and the 500, 400, 300, 100, and vertical shot tic marks being above the optical center. Much more precise shots can be produced much quicker between 0 and 600 yds. by not dialing with this self compensating geometry. The vertical shot tic mark, ( the very top line in the R2 is nothing more than the sight line which is parallel to the bore line when the scope is zeroed @ 600 and on full power.

When you get the load tuned right, the reticle will be more accurate than the 1/4 moa click resolution on the scope! IN EVEN 100 yd. increments that are simple to commit to memory

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S1
Member
Member # 963 posted 12-04-2002 01:52 AM

Brent

More on the R2 if your interested:
The method for ranging I use. Find the base number for the target you want to shoot.

This is the size from belly to back in inches divided by 2. Deer = 18" base # = 9
Elk = 36" Base # = 18
Place the reticle on the target, count the number of tic high and divide this into your base number and add two zeros.
EXAMPLE: The Bull elk I am looking at is 2 tic marks tall from belly to back. MY base number for elk is 18. 18/2 = 9 move the decimal two positions and you have 900 yds.
If the elk is 3 tics tall he is 600 yds away.
If he is 5 tics tall the elk is at 360 yds.

I use this method because it is easier than the method NF gives in their instructions and it is quicker for me to divide smaller numbers with this method in my head.


Brent
Member
Member # 85 posted 12-04-2002 02:51 AM

I'm not sure I follow you completely.
This is the drop chart the Oehler Ballistic Explorer gives me for a BC of .507 at 3380 fps at standard conditions.
100= -8.7MOA
200= -7.7
300= -6.2
400= -4.4
500= -2.3
600= 0.0
700= +2.5
800= +5.4
900= +8.5
1000= +12.0
I guess I expected to see the 100 yard increments fall on the 2 MOA tic marks magically.
Take the 800 yard hold over amount of +5.4MOA for example, are you supposed to hold 2 ticks (2 MOA per tic) above for 4 MOA and estimate the other 1.4 seeing's how the next tic is at 6 MOA?
When you get the load tuned right, the reticle will be more accurate than the 1/4 moa click resolution on the scope!
Can you explain how? I don't see why.
The vertical shot tic mark, ( the very top line in the R2 is nothing more than the sight line which is parallel to the bore line when the scope is zeroed @ 600 and on full power.
The program indicates 71.45" of drop at 600 yards. The bullet would hit around 11.45" low if the 10 moa tic mark above the center crosshair was was following the bore, true?
11.37 MOA is needed to account for the 71.45" of drop at 600 yards is all I'm trying to say, so it would appear that the bore line is somewhat higher than the 10 MOA tic mark if actually zeroed at 600 yards. It is close though. Correct me if I'm wrong.
The 220 smk is too heavy to integrate with the reticle below 6,000 ft. altitude
What happens if it is used? Does the 100 yard hold under go beyond the 10 moa tic mark?
We have to find you a load with the 180 that will get you between 3360 and 3400.
Can you explain why the 3200 fps load will not work as well.
Sounds very interesting so far. Thanks
--------------------
Brent

Posts: 562 | From: Palmer, Alaska | Registered: Jun 2001 | IP: Logged

Author Topic: Nightforce problems.???
S1
Member
Member # 963 posted 12-04-2002 03:25 AM

Brent

The software you are using is a good approximation tool, however it is relatively unsophisticated. The six degrees of freedom computer program we use takes some additional things into account. How the actual b.c. varies in flight, and the effect of the relationship of center of pressure to center of gravity and its interrelationship with the laws of gyroscopic precession. Mainly for these reasons I believe that the trajectory curve that you get in the real world will be a slightly different one than your computer is showing you.

You may change the actual bc (by more than .030) of a bullet by changing the
pressure and velocity it is fired at.

AS a trial, run a bc of .520 and a velocity of 3400 and see if the tic marks don't come within a 1/4 moa of your 100 marks.

More on this in just a minute...

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S1
Member
Member # 963 posted 12-04-2002 03:39 AM

The top tic mark (10 moa above the main crosshair)is for shooting off a cliff or sky scraper straight down, with your main zeroed at 600 yards. In a vertical shot straight up or down there is no gravity drop. It will not matter how far away the target is (within reason) the bullet will hit very close to the top mark. Very cool for counter terrorist work in big cities or mountainess terrain.

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Brent
Member
Member # 85 posted 12-04-2002 03:47 AM

You must have posted as I was typing, slowly .
It took me a minute to see what you were doing dividing by two, and at the same time keeping the results the same.
You are ruducing the object size number in half, and tics are 2 MOA apart, so counting them as "one" reduces them in half too. This does make it easier in the head. Thanks for the tip.
I've noticed that a mature moose is about 1/3rd deeper through the chest than a 2 yr old. I was looking at two different ones at 400 yards ranged with a laser, the reticle clearly showed the difference and by how much too. I think it was about 6 ticks vs. 4 ticks or real close to that.
We've ranged rims on our vehicles (no one in them of course) out past 1000 yards with the R2 while using the lasers to verify the distance and always were +-15 yards and we weren't even using a very good rest either.
Another pointer too is if you have a laser range finder and can range an animal accuratly, you can then measure it's head size, ear length, chest depth and OAL etc using the R2 reticle with amazing accuracy.
--------------------
Brent

Posts: 562 | From: Palmer, Alaska | Registered: Jun 2001 | IP: Logged


S1
Member
Member # 963 posted 12-04-2002 03:55 AM

Brent

Did the Oehler give you moa or did it give you inches and you converted the data to moa?

What sight height above the bore line is your data based on? this will have a large impact.

I believe the attainable velocity for the 220 gr.mk will be too slow and the trajectory will not work well with the R2 at sea level. It will not shoot flat enough in the first part of the trajectory. However don't forget about the 220s because the second you decide to hunt elk or something above 6,000, these bullets will be amazing with the R2 application!

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S1
Member
Member # 963 posted 12-04-2002 04:15 AM

Brent

I carried my vector IV for six days in 1998 and did not see a bull during daylight hours. On the last day we were at 12,500 ft. in thigh deep snow looking down towards the treeline at some large rockslides.

My buddy spotted 4 cows in a slide 3000 yards away. It took 4 hour to get within range I felt was a shure deal in the 30 to 40 mph wind conditions. I always heard these conditions pushed elk to lower altitudes, someone forgot to tell these elk.

AS luck would have it their was a nice 5X6 in with the cows. I whipped out my high speed range finder and ranged the bull at 36 yards! Then 28 yards, then 56 yards. Between the blowing snow, the snow falling, and the clouds enveloping us. The range finder I have trusted my life with was useless. The R2 however worked. It saved the hunt. I shot the bull through the heart at 525 yds. with a 200 gr. PRL tungsten with 5.5 moa of windage correction. What a DAY!

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Brent
Member
Member # 85 posted 12-04-2002 04:30 AM

I have several drag curves if you recommend one?
I can also enter multible BC's (5 seperate ones) at multiple VE ranges (5 also).
By the way, I'm getting a BC of .524 with the 180 Nosler BT and .576 with the 180 Scirocco at 3200 fps on the Oehler 43 both are at 63,000 psi. 96.5 and 97gr loads were at 70k psi and MV was 3347, how would I get 3400 with the same powder just changing primers, is it possible you think?
I shot the 180 BT at 600 yards, it took 9.75 MOA to zero it.
The results with a MV 3400 and BC .520 are...
100= -8.5
200= -7.6
300= -6.0
400= -4.2
500= -2.2
600= 0.0
700= +2.5
800= +5.2
900= +8.2
1000= +11.6
Are we looking for the 100 yard numbers to fall on the tics?
--------------------
Brent

Posts: 562 | From: Palmer, Alaska | Registered: Jun 2001 | IP: Logged


S1
Member
Member # 963 posted 12-04-2002 04:38 AM

Brent

What primer are you using now?

This last spread looks good, your dead on at 300 yds. and less than 1/4 moa at 500, 400, I am a little baffled about the 100 yd. data

What is the scope height assumption in the software?

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Brent
Member
Member # 85 posted 12-04-2002 04:50 AM

It will give total drop, bullet path and zero adj. in MOA as well as several other things also.
The sight hight was set at 1.5" which was wrong, it should be 1.79" measured above the bolt.
Nice shot on the elk there. The wind can be a big shutdown in this area at times too, the snow isn't a problem in aug-sept around here, farther up north it can be. Nice to have a "failsafe" no mater what.
--------------------
Brent

Posts: 562 | From: Palmer, Alaska | Registered: Jun 2001 | IP: Logged


S1
Member
Member # 963 posted 12-04-2002 04:58 AM

How close is Homer to Palmer?

If you have tested the scirocco and it has a higher bc, that will help. slightly higher rings will also fine tune the precision of the R2. What powder have you tried with the 180 scirroco? 2.0 to 2.1" is ideal for sight height.

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Brent
Member
Member # 85 posted 12-04-2002 05:01 AM

I've been using the Fed 215M.
I changed the sight height to 1.8 and the 100 yd zero went down to -8.2 and the 1000 yd went to +11.5.
Sounds like you boys were sheep hunting on that trip .
--------------------
Brent

Posts: 562 | From: Palmer, Alaska | Registered: Jun 2001 | IP: Logged


Brent
Member
Member # 85 posted 12-04-2002 05:07 AM

We're about 4 1/2 hours away from Homer. The road is pretty fast down that way now.
We're 45 min north of Anchorage.
--------------------
Brent

Posts: 562 | From: Palmer, Alaska | Registered: Jun 2001 | IP: Logged


S1
Member
Member # 963 posted 12-04-2002 05:15 AM

Brent

You can pick up velocity with less pressure by changing to a 210 primer.

The 185 berger has a better bc than the 180s in most rifles. worth checking out.

100 yd data makes more sense now.

I think you have the major concepts down, time to try it in the real world. Guys I train with this system break really precise shots in less than 3 seconds from when their spotter gives them the range data! If you think the system is cool now, wait till you hunted with it for 3 seasons with some time to tweak loads and collect relative air density data.

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Brent
Member
Member # 85 posted 12-04-2002 05:28 AM

Hey thanks for all the time and info, I'll work on it and see how it works out and maybe even try the 185 Bergers too. I'll be changing to the 210 as well, we'll see what happens to the psi, MV and SD.
I thought of trying the VV 500 series of powders too.
--------------------
Brent

Posts: 562 | From: Palmer, Alaska | Registered: Jun 2001 | IP: Logged


[ 01-15-2003: Message edited by: Brent ]
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