Re: S&B 5-25X56 how many MOA on base?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Aries64</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: skkeeter</div><div class="ubbcode-body">I'm caught up in an optics dilemma. I'm new on here so please go easy on my ignorance. I currently own 2 Nightforce NSX 3-15x that reside on my .308 bolt gun and my DTA .338lm. I'm shooting up to 1100 yards with my current setup, but am finally looking for some more magnification so I can "attempt" to stretch my DTA out to 2000m. I'm an Moa/Moa guy so I really want to stay with this system. I'm willing to spend a considerable amount of $ on a new quality optic.</div></div>
I'll go easy on you, just like I do on everyone. However, new here or not, <span style="font-weight: bold"><span style="font-style: italic">bth87</span></span> is correct and I don't blame him/her for telling you to use the <span style="font-style: italic">"Search"</span> function. A lot of people are just too lazy to search and want to be spoon-fed, and forum members get tired of the lazy attitude and lame excuse that <span style="font-style: italic">"the search function didn't turn up anything."</span> The <span style="font-style: italic">"Advanced Search</span> actually works very well <span style="font-weight: bold"><span style="font-style: italic">as long as the user exercises common sense and uses relevant "keywords" to search with.</span></span> Garbage-in, garbage-out. There are tons of <span style="font-style: italic">"Premier, S & B, or Nightforce"</span> ect, threads on Sniper's Hide and finding them is very easy.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: skkeeter</div><div class="ubbcode-body">I'm torn between the Schmidt Bender PMII 5-25x56 L/P P4 MOA DT CW FFP, and the Premier Heritage Tactical Scope 5-25x56 Illum. MOA Reticle PRH-10011. I'm not even sure if this Premier model is even available yet.</div></div>
Both the PMII and the Heritage scopes have been available with (matching) MOA Reticle & MOA Turrets for more than a year.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: skkeeter</div><div class="ubbcode-body">It looks like the S&B is available now through Eurooptic, but it only has 56 MOA of elevation travel. I've heard the S&B glass is unmatched, but know that 56 Moa of elevation travel won't get me out to the distances I want to shoot.</div></div>
The Elevation travel specification on the EuroOptic web site in incorrect, just as it is incorrect on most other vendor web sites who copied S & B scope specifications from the Schmidt & Bender web site instead of consulting the S & B catalog and verifying the data with S & B. It isn't <span style="font-style: italic">entirely</span> the vendors fault, as the S & B web site had inaccurate verbiage about the PMII 5-25X56mm's Elevation travel on one page of the PMII main page for years that could be confusing if one didn't read through the specifications, discover the discrepancy, and put two and two together.
However, I expect more from vendors - they should know more about the products they sell than the consumers. Especially considering the prices of optics. The good news is that S & B has a new web site, and while I haven't gone through it yet I surmise that the erroneous descriptions and incorrect data I saw in the past have probably been removed.
<span style="font-weight: bold">The Elevation travel on the PMII 5-25X56mm with Standard DT 1/4 MOA Turrets is IS NOT 56 MOA. It is 65 MOA.</span>
<span style="font-weight: bold">NOTE:</span> In reference to my statement directly above, I should re-phrase and say that <span style="font-weight: bold"><span style="font-style: italic">"for all practical purposes"</span></span> the 1/4 MOA version of the PMII 5-25X[56] has 65 MOA of Elevation adjustment. S & B service technicians have stated that the 1/4 MOA and 0.1 MRAD versions of the PMII 5-25X[56] DTs' use the same Erector Assembly (so they have the same <span style="font-style: italic">potential</span> amount of adjustment). However, the 1/4 MOA Turret "dial" has a stop pin at 65 MOA on the second revolution. Forcing the Turret past the stop pin will damage the Dial and Turret. Therefore, <span style="font-weight: bold"><span style="font-style: italic">"for all practical purposes"</span></span> the 1/4 MOA version of the PMII 5-25X[56] has 65 MOA of Elevation adjustment.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: skkeeter</div><div class="ubbcode-body"> The Premier has 96 Moa of travel which would do the job. My backup plan is to just stick with Nightforce and get the 5-22x56. What do you guys think? </div></div>
While I prefer PMIIs' to Premier scopes, I do think that Premier makes great scopes and that the 31 MOA Elevation adjustment advantage that the 1/4 MOA version Premier 5-25X[56] has over the 1/4 MOA version of the PMII 5-25X[56] is a big advantage in favor of the Premier. If it was me and I was going 0.1 MRAD I'd go with a PMII no contest.
Nightforce makes great scopes - super Quality Control, great turrets, excellent clarity, and a wide range of reticles. So far, Nightforce's only FFP scope is the (3-15X[50]) F1, and 15X on the top isn't nearly enough magnification for 2,000 meters. I don't know what your time frame is, but if you can wait until Nightforce releases their next FFP scope it could be the ticket.
I've owned and used a Premier Heritage 27 MIL DT MTC Gen 2 XR (CCW) alongside a PMII 5-25X56mm 26 MIL DT Gen 2 XR CCW, and the optical quality is so very close so it's really a "toss-up" between the two for optical performance. Both scopes possess traits that may or may not appeal to individual users. I prefer a PMII 5-25X[56] DT 0.1 MRAD Gen 2 XR CCW to the Premier, but YMMV. You have to get behind the respective potential scopes' side-by-side at the range, or at least see them both side-by-side at the store.
One thing that I will spoon-feed you is that you should use a 40-45 MOA base cant with a 1/4 MOA version of the PMII 5-25X[56]. Below is the correct procedure of how to determine and select the correct cant (forward slope) for your rifle in order to get full Elevation adjustment out of a PMII, which you will need in order to stretch out to 2,000 meters (especially if you handicap yourself with the 1/4 MOA version of the PMII). The 1/4 MOA version of the PMI 5-25X[56] has 65 MOA of Elevation adjustment, while the 0.1 MRAD version of the PMII 5-25X[56] has 26 MILs' (roughly equivalent to 90 MOA).
<span style="font-weight: bold">PMIIs' are designed and engineered to be used with aggressively canted bases. PMII variables' are preset at the S & B factory with their reticles' adjusted out-of-center by HALF of their FULL Elevation travel, giving them UPWARD Elevation bias. In order to compensate for this mechanical bias/offset, a base that approximates one half of each respective scope's full Elevation travel should be used.</span> However, its' a good idea to get a base with a few "extra" MOA built-in to allow for the travel you'll use to zero at 100 yards.
Selection of a base with the correct cant is all detailed in the <span style="font-weight: bold"><span style="font-style: italic">"
2006 PMII User Manual"</span></span> beginning on page 3 under <span style="font-weight: bold"><span style="font-style: italic">"Section 4.2"</span></span>, <span style="font-weight: bold"><span style="font-style: italic">"Adjustment range and forward angle"</span></span> and concluding on page 4. Italicized and in quotation marks below is the section I am speaking of. Below the text of Section 4.2 is a diagram from page 19 of the PMII User Manual showing <span style="font-style: italic">"picture 2"</span>, <span style="font-style: italic">"picture 3"</span>, and <span style="font-style: italic">"picture 4"</span> as referenced in the (2006) User Manual. Keep in mind that the Manual does not allow for any travel used to "zero" the scope as I did in my paragraph above.
<span style="font-weight: bold"><span style="font-style: italic">"4.2. Adjustment range and forward angle
Scopes for high precision shooting are often used for shooting at great
distances. In this case the elevation adjustment is used to compensate for bullet
drop. To provide an extensive elevation range in these scopes Schmidt &
Bender has increased the main tube diameter from 30mm to 34mm.
Nevertheless the elevation and windage range like in any other scope is limited.
In scopes for hunting the reticle is generally centered optically and mechanically
in order to receive the same amount of travel in all directions and to make the
mounting of the scope to the firearm easier (see picture 2).
In order to make the elevation adjustment range usable in its full extent it is
necessary to preset the reticle of the PMII scopes out of the center already at
the Schmidt & Bender factory (see picture 3). As a consequence the gunsmith
is obliged to consider the preset position of the reticle in the elevation range
when mounting the scope to the firearm (see picture 4). With this setup the full
elevation range is usable in one direction allowing to shoot at distances up to
2000m depending on the used calibre and scope type.
Determining the correct forward angle
The necessary forward angle is depending on the used type of elevation
adjustment. At the Schmidt & Bender factory the reticles of PMII scopes are
adjusted out of center by half the amount of the full elevation range. This value
must be compensated in the mount system.
Forward angled mounts or rails for every Schmidt & Bender PMII scope type
are available from all renowned mount manufacturers.
Example for determining the required forward angle:
A standard elevation turret (Single Turn) with an elevation range of 13mrad
(equals 130cm at 100m distance) requires a forward angle of 65cm at 100m
(equalling the half of the full elevation range). For a gunsmith compensating for
this value using the mounts the following rule of thumb applies: If the space
between the two mount rings is 100mm the front mount should be 0.65mm
lower than the rear mount.
If the gunsmith is using a forward angled rail standard mount rings without
forward angled can be used."</span></span>
<span style="font-weight: bold"><span style="font-style: italic">"picture 2"</span>, <span style="font-style: italic">"picture 3"</span>, and <span style="font-style: italic">"picture 4"</span> as referenced in the <span style="font-style: italic">2006 PMII User Manual:</span></span>
<span style="font-weight: bold"><span style="text-decoration: underline">NOTE:</span></span> <span style="font-weight: bold"><span style="font-style: italic">In the diagram above:</span></span>
<span style="font-weight: bold">"<span style="color: #FF0000">Picture 2</span>"</span> shows a scope mounted on a rifle with a flat (non-canted base). The drawing illustrates a typical scope with optically-centered reticle and erector. Personally, I always use canted bases, as they have no downside - they don't adversely affect 100 yard zeroing and shift a bit of Elevation travel to the upper end of the scope's adjustment range. <span style="font-weight: bold"><span style="font-style: italic">PMIIs' are actually designed to use agressively-canted bases.</span></span>
<span style="font-weight: bold">"<span style="color: #FF0000">Picture 3</span>"</span> shows a scope mounted on a rifle with a flat (non-canted base). The drawing illustrates the effect that the PMII's Reticle offset (PMII reticle's are preset at the factory <span style="text-decoration: underline">biased towards the top of the scope tube</span>) has upon the PMII's operation and the PMII's requirement for specific cant scope bases. This mechanical offset is engineered into the PMIIs' and requires use of specific cant bases in order to get optimum Elevation travel out of respective PMII scopes. The Reticle's off-center orientation (towards the top of the tube) means that you're actually looking very slightly upward when you look through a PMII at the bottom of it's travel, and that the Reticle's LOS (Line-of-Sight) won't intersect the projectile's trajectory without a lot of "UP" adjustment. Obviously, the scope's offset over the bore will require the shooter to use a lot of "UP" adjustment to zero the rifle. Use of a correct cant base eliminates these issues and allows the PMII to function as designed.
<span style="font-weight: bold">"<span style="color: #FF0000">Picture 4</span>"</span> shows a scope mounted on a rifle with a canted base. The drawing illustrates how the use of a base with the correct cant affects the PMII Reticle's LOS (Line-of-Sight) and allows the respective PMII access to it's full Elevation adjustment range. The Reticle is still oriented at the top of the scope tube, but the canted base has angled the scope (and Reticle) slightly downward in relation to the axis of the bore, allowing the Reticle's LOS (Line-of-Sight) to intersect with the projectile's trajectory. The scope can now be "zeroed" with minimal Elevation adjustment. After the scope is zeroed, the Elevation Turret shoud be set to "0". Scopes with DT (Double Turn) Elevation Turrets should be reset.
Also, the illustrations show the bullets arcing upward from the axis of the bores. This, of course - does not occur in real life. I'm sure that the gravity-defying bullets were drawn in that manner to simulate the arc of the rounds as they travel downrange.
<span style="font-weight: bold"><span style="font-style: italic">The math:</span></span>
65 MOA = 65 x 1.047" = 68.055"
68.055" divided by 2 = 34.0275"
Add 5 MOA for a 100 yard zero (common example) and you want about a 40 MOA base cant.
Keith </div></div>
