Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Hunting > Long Range Hunting & Shooting

Long Range Hunting & Shooting Nightforce Optics


Reply

Sanity test, Scope adjustment compensation.

 
LinkBack Thread Tools Display Modes
  #1  
Old 11-07-2012, 07:23 AM
Platinum Member
 
Join Date: Jan 2008
Location: Northeast
Posts: 2,331
Sanity test, Scope adjustment compensation.

Testing my Mark 4 for click value/turret adjustment accuracy I found the each click value is actually .262 MOA as opposed to .25 MOA. After going through some math and checks on my Ballistics Calculator I found that I could use my MOA turrets with MOA entered into the BC and replicate my drops out to at leat 1000 yards by reducing my velocity entry by 50 FPS. Better yet I could as an alternative use the IPHY entry in my calculator since the difference is 1.048" per click, since .25"x1.047= .262. This replicated the drop in inches at 1000 yards. The IPHY difference to MOA is 1.047 which puts the actual drop within 1" at 1000 yards. Coincidence? My load is .338 Lapua, 300 Berger, actual velocity 2700 FPS. I will do an actual drop test to confirm this but I wanted to sanity test my logic. Does this make sense?
__________________

"Let us speak courteously, deal fairly, and keep ourselves armed and ready"-T. Roosevelt
Reply With Quote
  #2  
Old 11-07-2012, 10:21 AM
Platinum Member
 
Join Date: Mar 2008
Location: SW Idaho
Posts: 1,151
Re: Sanity test, Scope adjustment compensation.

I may be reading your info wrong but I think you are making it harder than it is.

1 MOA = 1.047 inches per 100 yards, so each MOA click is .262 inches, assuming the scope is calibrated correctly.
1 IPHY = 1.0 inch per 100 yards, so each IPHY click is .25 inches, assuming the scope is calibrated correctly.

So if your turrets click adjustment moves .262 per click then it is actually moving what it should for true MOA.

So to test this you can either shoot to find drops or just measure the change in the reticle as you move your turrets. I prefer to just measure the movement as it saves me shooting ammo and keeps shooter error out of the equation. Set up your target, for me a tall piece of cardboard, at exactly 100 yds. Buy or print out 1/4 inch graph paper, make sure it measures true, and piece enough together to get 30 inches. You can buy it large enough but if I print it I have to piece it together. Mark your start point on the graph paper so you don't loose it and then dial in say 20 MOA. Then measure the distance your reticle moved. Then take that distance, divide it by the number of clicks, 80 in this example, and you have your true movement per click in inches. So if your reticle moved 21 inches you would have a click value of .2625 which is very close to true MOA. if it moved 20 inches it would be IPHY or .25 inch per click. If it moved 22.5 inches your click value would be .281.

If you want to shoot instead of measuring you simply shoot a base group then dial 20 MOA then measure the distance between the two groups, then divide that number by the number of clicks.

With some ballistic programs you can actually enter in the true correction per click that you just calculated get the program to read correctly, ie enter .262 or .25 or .281. Other programs want you to come up with a correction factor which requires you to find the error % and then enter that, ie .262 (true MOA) divided by .281(the actual click value you determined) = .929. Then your data card will show correct drops assuming other data is accurate.

Clear as mud?

Scot E.
Reply With Quote
  #3  
Old 11-07-2012, 11:16 AM
Platinum Member
 
Join Date: Jul 2009
Location: GEORGIA
Posts: 1,206
Re: Sanity test, Scope adjustment compensation.

When I was figuring my drops for my custom turret on JBM and got the drop measurements. Then went to the range to actually shot and measured "MY" rifles drops with a 200 yd. zero and found that "MY" rifle actually dropped more than the JBM program at 200 & 400 yards. I gave the actual measured drops to Vortex so they could match the arc of my bullets path to the custom turret.

This worked more accurate than the JBM program because when I shot at all 100 yard distances out to 900 yds and the elevation was spot on.

joseph
Reply With Quote
  #4  
Old 11-07-2012, 12:18 PM
Bronze Member
 
Join Date: Apr 2012
Location: Arizona
Posts: 44
Re: Sanity test, Scope adjustment compensation.

Hey guys thanks for the great information. This saved me from a Maalox moment.....Really.
Reply With Quote
  #5  
Old 11-08-2012, 06:43 AM
Platinum Member
 
Join Date: Jan 2008
Location: Northeast
Posts: 2,331
Re: Sanity test, Scope adjustment compensation.

I had an error in my original calculation. At 200 yards 44 clicks resulted in 23.5" which calculates to .267" per click. This translates to a +.5 MOA error with my load that results in the bullet impacting high. I don't have the option in my G7 Br2 rangefinder of adjusting the internal calculator, but can achieve the correction by adding 20 FPS to my velocity input. I will verify this at the range to get actual impact points when I can get to the range. Thanks for the feedback!
__________________

"Let us speak courteously, deal fairly, and keep ourselves armed and ready"-T. Roosevelt
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Sanity test, Scope adjustment compensation.
Thread Thread Starter Forum Replies Last Post
Scope Adjustment rick523 General Discussion 12 10-23-2012 02:27 PM
Scope Adjustment, Range, and Scope Bases 270 MKV Long Range Scopes and Other Optics 2 09-27-2012 09:59 AM
Tac 15i ran out of scope adjustment Kytopgun PSE TAC 15/15i Crossbow Hunting Forum 2 10-10-2011 11:47 AM
scope cant compensation wildchild General Discussion 5 04-18-2011 05:11 PM
more scope adjustment? dodgefreak8 Long Range Scopes and Other Optics 5 10-25-2005 05:53 PM


All times are GMT -5. The time now is 12:06 PM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC