Rifle Scopes Avg Scope Elevation Loss

[Youngjoonni]

Wanted to see how much elevation loss people have on their setup @ their zero.

My setup:

Rem 700 .308
20 MOA BO base
1" BO rings
S&B PMII 5-25x56 CCW MOA
Southwest 175gr SMK ammo

100yd Zero: 42.75 MOA on scope +20 MOA base = 62.75 total MOA

Seems excessive. Thoughts?

 

[RTS]

Re: Avg Scope Elevation Loss

That's about what I get on my Rem 700 with a NF. To take shots past that, I have to hold high. I think I have 25 minutes on the reticle additional available at ranging power.

 

[Youngjoonni]

Re: Avg Scope Elevation Loss

Looks like I'll be changing bases and installing my AI 1 piece setup which has a 45 MOA cant.

Edit... After crunching some number, I don't have to change the base. 65 MOA - 62.75 MOA = 2.25 MOA @ 100 yds with a .308 175 gr FGMM which gives me a 200yd zero. I can live with that.

Thanks for your input!

 

[BobinNC]

Re: Avg Scope Elevation Loss

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Youngjoonni</div><div class="ubbcode-body">Looks like I'll be changing bases and installing my AI 1 piece setup which has a 45 MOA cant. </div></div>

Before you go running off and swapping bases, please confirm your numbers, and scope model.....

The reason I ask that is reading some of your earlier posts you indicate your using a S&B PMII 5-25x56mm MOA.

That particular scope has 56 MOA of total adjustment according to S&B, "The 5–25 x 56 is offered with 56 MOA of 1/4 MOA clicks, or 273cm (93 MOA) of 1cm clicks."

Now 56 MOA is split 28 moa up and 28 moa down. With a 20 MOA base, you should have 48 MOA up and 8 MOA down. If according to your first post have 42.75 MOA left, then you used 5.25 MOA to zero, which is not excessive.

Put a 45 MOA base on a 56 MOA scope, and you will not be able to achieve a 100 yd zero.

Remember a canted base does not ADD MOA to your scope. It just takes from the DOWN MOA adjust and adds to the UP adjust. Your scope will still only have a total of 56 MOA travel with a 0 MOA, 20 MOA, or 45 MOA base......

 

[Youngjoonni]

Re: Avg Scope Elevation Loss

BobinNC, I do not have 42.75 MOA left, it is the amount of MOA required to zero at 100yds with a 20 MOA base and 1" high rings.

56 MOA - 42.75 MOA = 13.25 MOA or so left on the elevation turret. That will get me out to under 600yds which is fine for this hunting but it does not utilize the full potential of the rifle or scope. That's a no go in my book.

I've read conflicting info as to which various cants are required in order to optimize the S&B scopes. I just talked to Mark @ S&B about my concern. He stated that a 20 MOA base works fine for the PMII line but recommends a 45 MOA base to optimize the 5-25x56 model for 2K meters.

 

[timelinex]

Re: Avg Scope Elevation Loss

Check to make sure you didn't put your base on backwards, you should have way more than that left...

 

[BOLTRIPPER]

Re: Avg Scope Elevation Loss

wow,,,,,just wow......

 

[abersfelderami]

Re: Avg Scope Elevation Loss

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: timelinex</div><div class="ubbcode-body">Check to make sure you didn't put your base on backwards, you should have way more than that left... </div></div>

or your front ring isn't mounted right.

 

[Youngjoonni]

Re: Avg Scope Elevation Loss

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: abersfelderami</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: timelinex</div><div class="ubbcode-body">Check to make sure you didn't put your base on backwards, you should have way more than that left... </div></div>

or your front ring isn't mounted right. </div></div>

Base has been bedded to the action perfectly. Didn't even know you could put it on backwards!

As to the front ring not mounted correctly...it is correct.

Keep the inputs coming!

 

[abersfelderami]

Re: Avg Scope Elevation Loss

Pictures?

 

[gstaylorg]

Re: Avg Scope Elevation Loss

With a properly mounted 20 MOA base, it should take in the neighborhood of 18-22 MOA <span style="font-style: italic">down</span> on your elevation turret to achieve a 100 yd zero. If the scope came from the factory optically centered, the 20 MOA base will raise your POI by ~20 MOA prior to any adjustment of the elevation turret. At 100 yd, your first shot prior to any adjustment of the scope should have been somewhere around 20" high. Is that anywhere close to what you actually observed? If not, compare what you did actually observe to that number and it might give you some clue as to what is going on.

As far as a 45 MOA base and 2K meters, it's a .308. Do you really think it's necessary to set it up for anything past 1000 yd or so? You'll be much better off working within the ballistic parameters of the .308 load in order to optimize your setup.

 

[Aries64]

Re: Avg Scope Elevation Loss

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Youngjoonni</div><div class="ubbcode-body">Wanted to see how much elevation loss people have on their setup @ their zero.

My setup:

Rem 700 .308
20 MOA BO base
1" BO rings
S&B PMII

100yd Zero: 42.75 MOA on scope +20 MOA base = 62.75 total MOA

Seems excessive. Thoughts?



</div></div>
<span style="font-weight: bold"><span style="font-style: italic">Youngjooni</span></span> -

Which model and version PMII are you using? You really need to clarify which PMII is mounted on the subject rifle. From reading your posts within this thread I surmise that the scope mounted on the subject rifle is a PMII 5-25X with .25 MOA turrets. The only way I figured that out is by reading through the thread (which I usually do by most people don't). Only the PMII 5-25X LP DT .25 MOA version has 65 MOA of Elevation travel. In the future please state the specifics. This will help facilitate getting you correct/accurate answers to your inquiry. That way we don't have to rely upon <span style="font-style: italic">The Force</span>.

That said, <span style="font-weight: bold"><span style="font-style: italic"> in order to be able to access the full (65 MOA) of travel that a PMII 5-25X with .25 MOA turrets has, the ideal base would be one with a cant of 33-35 MOA.</span></span> Why? Because PMIIs' are designed and engineered to be used with aggressively canted bases. While most scopes are geared towards hunting applications and have the Reticle <span style="font-style: italic">optically</span> and <span style="font-style: italic">mechanically</span> centered in the maintube, <span style="font-weight: bold">PMIIs' 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>

That is why S & B recommends the use of a 45 MOA base for the 0.1 MIL version of the PMII 5-25X DT (Double Turn), and why AI sells a 45 MOA base for use with the (0.1 MIL) PMII 5-25X. A 4-16X 0.1 MIL works best with a 25-30 MOA base, while the 3-12X (0.1 MIL) works best with a cant of 40-45 MOA. The 3-20X should be GTG between 40-45 MOA, but I haven't mounted and used one yet. You will use a small amount of adjustment to zero, but the above will get you really close. I use a 40 MOA base on my Tac Ops X-Ray 51 (.308) and zeroed at 100 yards using FGMM 175s' I have 26.4 MILs' of actual Elevation travel. I also have two clicks below zero ("absolute" zero). This varies slightly between ammo lots/loads, but 26 MILs is much more than I can possibly use with a .308. I could get another MIL or so back if I use a Tac Ops 45 MOA base. I might do that since my X-Ray 51 is being re-fitted...

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.

<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>

I hope this post clears-up any confusion members may have about the use of canted bases and the correct base cant for use with PMIIs', as well as to help guide new PMII owners' and would-be PMII owners' towards the selection of the correct base for use with their PMII.


<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 dont 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="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.


Keith

 

[Youngjoonni]

Re: Avg Scope Elevation Loss

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: abersfelderami</div><div class="ubbcode-body">Pictures? </div></div>

Pic of current 100yd settings as requested.

 

[Youngjoonni]

Re: Avg Scope Elevation Loss

Not sure as to why it would matter but a pic of my setup.

 

[Youngjoonni]

Re: Avg Scope Elevation Loss

OP updated with scope model.

Sorry for the confusion. No good reason as to why I didn't complete the scope description.

Anyway, it wouldn't have been much of an issue if I had at least 47 MOA of elevation travel which would allow full use of the 308. But since this was not the case, I wanted to cover my bases before having my gunsmith look into it later on.

 

[Youngjoonni]

Re: Avg Scope Elevation Loss

Since I brought my rifle out I decide to continue setting the scopes zero. I loosened the turrets and reset them to "0". I then rotated the turrets to evaluate the amount of actual adjustment left in them and, to my surprise, I have full adjustment! Now, I feel like an idiot though a happy one!

Could someone explain to me how this is so?

BTW, even though I've had this scope for over a year now this is the first opportunity I've had to try her out. This is also my first S&B as you may have surmised.

 

[Aries64]

Re: Avg Scope Elevation Loss

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Youngjoonni</div><div class="ubbcode-body">Since I brought my rifle out I decide to continue setting the scopes zero. I loosened the turrets and reset them to "0". I then rotated the turrets to evaluate the amount of actual adjustment left in them and, to my surprise, I have full adjustment! Now, I feel like an idiot though a happy one!

Could someone explain to me how this is so?

BTW, even though I've had this scope for over a year now this is the first opportunity I've had to try her out. This is also my first S&B as you may have surmised. </div></div>
With regard to you having "full adjustment", it sounds like you inadvertently (but necessarily) reset the DT turret.


Keith

 

[sobrbiker883]

Re: Avg Scope Elevation Loss

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BOLTRIPPER</div><div class="ubbcode-body">wow,,,,,just wow...... </div></div>

 

[Youngjoonni]

Re: Avg Scope Elevation Loss

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Aries64</div><div class="ubbcode-body">
With regard to you having "full adjustment", it sounds like you inadvertently (but necessarily) reset the DT turret.


Keith </div></div>

Not exactly sure what you mean by "inadvertently" but it seems to be resolved.

My confusion stems from knowing that these scopes have 65 MOA elevation adjustments. If I use "x" amount in order to achieve a 100yd zero, should it not be subtracted from the 65 MOA total? Ie... 65-42.75= 22.25 moa travel left inside the scope.

Do the turrets act as limiters for the moa models? It would correspond with the total adjustment variations between the mil vs moa s&b technical specs chart.

 

[Aries64]

Re: Avg Scope Elevation Loss

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Youngjoonni</div><div class="ubbcode-body">
With regard to you having "full adjustment", it sounds like you inadvertently (but necessarily) reset the DT turret.


Keith </div></div>
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Youngjoonni</div><div class="ubbcode-body">Not exactly sure what you mean by "inadvertently" but it seems to be resolved.</div></div>
My use of <span style="font-style: italic">"inadvertently"</span> (as in <span style="font-style: italic">without knowledge or intention</span>) was in reference to your <span style="font-style: italic">"surprise"</span> of having <span style="font-style: italic">"full adjustment"</span> after resetting the (DT) Elevation Turret. The fact that you were suprised that your scope had full adjustment travel after resetting the Elevation Turret indicates that: (a) you did not know how to reset the Elevation Turret, and (b) that resetting the Elevation Turret would "get your travel back".

I thought that you had tried resetting the Elevation Turret prior to posting, but obviously that wasn't the case. BTW, resetting of the DT Elevation Turret on PMII scopes is normally accomplished by loosening the two (2) screws that secure the Elevation Turret dials to the turret, then turning the Elevation Turret a couple of revolutions in the opposite direction of "UP". Rotating the <span style="font-style: italic">Elevation Dial</span> without engaging Turret itself ensures that a notched pin housed in the underside of the Elevation Dial is engaged and reset. This notched pin is what changes the color in the "windows" to indicate whether the scope is on the first or second revolution of travel.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Youngjoonni</div><div class="ubbcode-body">My confusion stems from knowing that these scopes have 65 MOA elevation adjustments. If I use "x" amount in order to achieve a 100yd zero, should it not be subtracted from the 65 MOA total? Ie... 65-42.75= 22.25 moa travel left inside the scope.</div></div>

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Youngjoonni</div><div class="ubbcode-body">
With regard to you having "full adjustment", it sounds like you inadvertently (but necessarily) reset the DT turret.


Keith </div></div>
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Youngjoonni</div><div class="ubbcode-body">Not exactly sure what you mean by "inadvertently" but it seems to be resolved.</div></div>
My use of <span style="font-style: italic">"inadvertently"</span> (as in <span style="font-style: italic">without knowledge or intention</span>) was in reference to your <span style="font-style: italic">"surprise"</span> of having <span style="font-style: italic">"full adjustment"</span> after resetting the (DT) Elevation Turret. The fact that you were suprised that your scope had full adjustment travel after resetting the Elevation Turret indicates that: (a) you did not know how to reset the Elevation Turret, and (b) that resetting the Elevation Turret would "get your travel back".

I thought that you had tried resetting the Elevation Turret prior to posting, but obviously wasn't the case. BTW, resetting of the DT Elevation Turret on PMII scopes is normally accomplished by loosening the two (2) screws that secure the Elevation Turret dials to the turret, then turning the Elevation Turret a couple of revolutions in the opposite direction of "UP". Rotating the <span style="font-style: italic">Elevation Dial</span> without engaging the Turret itself ensures that a notched pin housed in the underside of the Elevation Dial is engaged and reset. This notched pin changes the color in the "windows" to indicate whether the scope is on the first or second revolution of travel.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Youngjoonni</div><div class="ubbcode-body">My confusion stems from knowing that these scopes have 65 MOA elevation adjustments. If I use "x" amount in order to achieve a 100yd zero, should it not be subtracted from the 65 MOA total? Ie... 65-42.75= 22.25 moa travel left inside the scope.</div></div>
Yes - <span style="font-weight: bold"><span style="font-style: italic">in theory</span></span> you subtract the amount of travel you used to zero. However, scopes typically have a bit of variance in the available travel, and your scope may have a bit more (or less) than specified.

<span style="font-weight: bold">More importantly, you actually only start-out with full travel (65 MOA for your scope) if you have your scope mounted with an appropriately canted base.</span> Perhaps you didn't read and/or understand the except I quoted from the PMII Manual in my first reply to you in this thread. For your scope the theorietical ideal would be 32.5 MOA (one half of the total adjustment), but that formula doesn't factor-in any adjustment used while zeroing. If I had your scope I would use a base with a cant between 35 and 40 MOA, as the "extra" cant would help compensate for the adjustment used while zeroing while not adversely affecting the travel on the upper end of the Elevation travel.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Youngjoonni</div><div class="ubbcode-body">Do the turrets act as limiters for the moa models? It would correspond with the total adjustment variations between the mil vs moa s&b technical specs chart.</div></div>
Aside from the adjustment increments the construction of the turrets should be the same between the MOA and MIL-based versions. The MIL-based PMIIs' have a greater adjustment range within the given models because the 0.1 MIL adjustment is more coarse than the .25 MOA adjustment. Also keep-in-mind that the 20 MOA base that you're using is less than the recommended (as well as an <span style="font-style: italic">ideal</span>) cant for use with your PMII 5-25X.


Keith

 

[Youngjoonni]

Re: Avg Scope Elevation Loss

Appreciate your input, Keith.

 

[Aries64]

Re: Avg Scope Elevation Loss

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Youngjoonni</div><div class="ubbcode-body">Appreciate your input, Keith.

</div></div>
No problem. For further clarification of the illustrated diagram from the PMII Manual and how the PMII's <span style="font-weight: bold"><span style="font-style: italic">reticle bias</span></span> works with canted bases please read the info below. I also added this info to my first reply to you in this thread as a <span style="font-style: italic">"NOTE:"</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="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 dont 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="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.


Keith