M1A (M21) .308 Load, and Long Range Optics choices
03-14-2010, 12:24 PM
Join Date: Jan 2008
M1A (M21) .308 Load, and Long Range Optics choices
My Springfield M1A (M21) can group well under an inch with 168 SMKs, Lapua brass, CCI 34 primers, and 40.5 grs. of H4895.
I haven't tried past 100 yards yet, but, since I've been looking at buying a Zeiss Conquest Rapid Z 800 or Z 1000 scope, the dope on their website has caused me to recently write the following:
'Been doing some hunting for the best scope for my Springfield M1A (M21).
Springfield Armory Rifles
ZEISS RAPID Z 1000 RETICLE vs. RAPID Z 800 RETICLE
Both are around $925
And both are 4.5-14x50
Note: Please enter your information into our Rapid-Z Calculator to ensure that you make the best possible reticle selection
based on your caliber, bullet, hunting conditions and location.
Zeiss Calculator: http://www.zeiss.com/c1256bcf0020be5f/Contents-Frame/46cbcef61def2b88852574f700589d31
Calculator instructions: http://exbalapplications.com/ZeissWeb/(S(cdcd0d55lurh5i55lo5kofnq))/data/Instructions-English.pdf
According to their calculator for the Rapid Z 1000 (designed for the .308 Match ammo):
This IS the value for .308, Sierra 168-gr. MK (BC =.462),
Velocity: 2,550 fps,
Elevation: 4,500 ft. ASL
Temp: 80 degrees F
Zeiss Rapid Z 1000 (Click below to see reticle):
Zeiss | 4.5-14x50 AO MC Conquest Riflescope | 52 14 90 9973
With their calculator, and the scope power ring set to 11.8x (12 power):
*Optimize Power for: Bar No. 10 - Distance 1,000.
They say to zero dead-on at 500 yards with the Bar 5. (Bar 5 is the Center Crosshair.)
Easier way: To zero Bar 5 @ 100-yards:
On 11.8x (12 power): make bullet impact 11.87" high @ 100 yards (above Bar 5 - Center Crosshair).
Then this will happen:
At Bar 1, the bullet will impact at 139 yards - (and you can roughly zero at 139 yards with Bar 1, on 11.8x (12 power).
(Bars 1 - 4 are above the center crosshair Bar 5.)
Bar 2 = 218 yards
Bar 3 = 313
Bar 4 = 404
Bar 5 = 500
Bar 6 = 597
Bar 7 = 695
Bar 8 = 796
Bar 9 = 897
Bar 10 = 1,000 yards
This is seemingly unbeatable.
Now, with the Rapid Z 800 (Click below to see reticle):
With the M1A, same load, they say to put the power ring at 7.45 power.
*Optimize Power for: Bar No. 8 - Distance 800.
Sight in at 1.77" high @ 100 yards for a 200 yard zero (Center Crosshair - call it Bar 1).
(All other Bars are below the center crosshair - Bar 1.)
Watch it fall into place:
At Bar 2 (an unmarked bar), bullet will impact at 295 yards.
Bar 4 = 395 yards
Bar 5 = 495
Bar 6 = 596
Bar 7 = 698
Bar 8 = 800 yards
I know it's not a 1,000 yard reticle - but 'tis rather versatile anyway...
So, I'm deciding on which to choose.
More field of view and low-light capability with the power ring set at 7.45x with the Z 800 bullseyes, than at 11.8x with the Z 1000 bullseyes.
And they say the Z 800 is intended for other calibers; yet, look what it does for the .308!
But, with the Z 1000, there is more magnification (11.8x) for long distance at each Bar (stadia).
But, if you definitely need it backed-off at the lowest 4.5 power also, then the Z 800 will work for both close-quarter, and long-range work.
At 4.5 power, just use the center crosshairs for 0-300 yards - then for precision: Zoom to 7.45x for 200 to 800+yards.
Q. What would the Z 1000 do at 4.5 power? - when it is set up for all ranges (100-1000) at 11.8 power?
A. Dead-on at 500-yards ONLY - Center Crosshairs - Bar 5. (Bar 5: bullet impacts 11.87" high @ 100 yards when set at ANY magnification (4.5x - 14x). -Would need to test point of impact of Bars 1-4 on 4.5x ).
Maybe we can't have our convenient cake, and eat it too.
So, for me, THE DECISION IS: Z 800 !
The Z 800 is more traditional and more useful under stress. Your short-range field of view (FOV) and accuracy (at 4.5 power) could mean everything.
I'd stress more over the up-close and personal - than sweat the remaining 200 yards down range to the magic 1,000 marker.
And, I could live with the Z 800 at 7.45x to be sure for 0 to 800+yards. -You know what it's gonna do on 4.5x and 7.45x before you ever mount the scope!
With the Z 800, at ANY set magnification (4.5x - 14x), with the center crosshairs, the bullet will still impact 1.77" high @ 100-yards, and will still be absolute bullseye at 200-yards!
But, for a dedicated Long Range benchrest set-up - or if you don't mind having it at 11.8 power all of the time, the Z 1000 bullseyes scratch the 1,000-yard itch.
For users who want to know more about how their rifle will perform, a ballistics program (Exbal) from http://www.perry-systems.com/ with calculations for all Rapid Z reticles should be purchased. You can explore wind effects; get a profile of trajectory, velocity, energy, time of flight, etc… vs. distance to target. It also has an extensive ballistic reticle function to determine the point blank range data for each of the cross-bars or hashmarks on Rapid Z ballistic reticles for a specified target height.
LRB 7x50 laser rangefinder binoculars
Last edited by G-gear; 03-24-2010 at 10:35 AM.
Reason: Updated & Corrected Ballistics Data