Help to verify a zero

cmr287 · August 30, 2015, 08:55 PM

I zeroed my 20" barreled Rem 700 SPS Tac .308 @ 100 meters with a 150 gr Rem express PSP round with a BC .314.
My range data after shooting it came out to:

Range in Meters Drop Velocity
0-Muz 0.0 2820
100 0.0 2541
200 -1.7 2278
300 -4.5 2031
400 -7.0 1800
500 -11.9 1589
600 -16.9 1402

This was done 6 months ago, I haven't touched my rifle after I zeroed it except clean it before I picked it up for deer season. I don't have access to 100 Meters any more, however I have access to 25 meters.

If I am to verify my 100 meter (Z) at 25 meters I need to shoot 4" below center of target?

If I am to verify my 100 meter (Z) at 50 meters I need to shoot 2" below center of target?

Is this correct?

The Old Salt · September 5, 2015, 03:28 PM

Plugged some info into my Sierra Ballistic software for you. I have it set up for yards instead of meters, but this will be close.
I used:
your I.V. 2820 fps,
Sight center line of bore center line of 1.6",
Sighted in @ 100 yrds
Sierra 150g SPT with a BC of 0.346 above 2600 fps bullet.
Results:
Range Path Vel
20 yrd -0.90" 2765
30 yrd -0.62" 2737
50 yrd -0.20" 2683

Your numbers will be a little different, but at this speed and range the variance will be small. If you are going to check your sights before you go hunt, this would provide you a quick check, but a 100 yrd or meter range would do you better. The Sierra software is not that expensive, comes with a nice manual, and gives ballistic info out to 1000 yards.

The Big D · September 5, 2015, 06:36 PM

There is no possible way you will be 4in low at 25 or 2in low at 50. I don't know what your sight height above bore is, but in both cases you will be low by LESS than your height above bore since the bullet is rising during that part of the trajectory.

**JohnKSa** · September 6, 2015, 02:49 AM

Quote:

0-Muz 0.0 2820
100 0.0 2541

That can't be right. The bullet starts out below the sights by the amount of the height of the sights above the bore.

August 30, 2015, 08:55 PM	#1
cmr287 Junior Member Join Date: May 12, 2013 Posts: 7	Help to verify a zero I zeroed my 20" barreled Rem 700 SPS Tac .308 @ 100 meters with a 150 gr Rem express PSP round with a BC .314. My range data after shooting it came out to: Range in Meters Drop Velocity 0-Muz 0.0 2820 100 0.0 2541 200 -1.7 2278 300 -4.5 2031 400 -7.0 1800 500 -11.9 1589 600 -16.9 1402 This was done 6 months ago, I haven't touched my rifle after I zeroed it except clean it before I picked it up for deer season. I don't have access to 100 Meters any more, however I have access to 25 meters. If I am to verify my 100 meter (Z) at 25 meters I need to shoot 4" below center of target? If I am to verify my 100 meter (Z) at 50 meters I need to shoot 2" below center of target? Is this correct?

September 5, 2015, 03:28 PM	#2
The Old Salt Member Join Date: January 2, 2015 Location: NW Missouri Posts: 57	Plugged some info into my Sierra Ballistic software for you. I have it set up for yards instead of meters, but this will be close. I used: your I.V. 2820 fps, Sight center line of bore center line of 1.6", Sighted in @ 100 yrds Sierra 150g SPT with a BC of 0.346 above 2600 fps bullet. Results: Range Path Vel 20 yrd -0.90" 2765 30 yrd -0.62" 2737 50 yrd -0.20" 2683 Your numbers will be a little different, but at this speed and range the variance will be small. If you are going to check your sights before you go hunt, this would provide you a quick check, but a 100 yrd or meter range would do you better. The Sierra software is not that expensive, comes with a nice manual, and gives ballistic info out to 1000 yards.

September 5, 2015, 06:36 PM	#3
The Big D Junior member Join Date: July 19, 2015 Posts: 173	There is no possible way you will be 4in low at 25 or 2in low at 50. I don't know what your sight height above bore is, but in both cases you will be low by LESS than your height above bore since the bullet is rising during that part of the trajectory.