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Rifle Scopes Only 5.5 mil left after sight in

F

freeflight

Sergeant
Full Member
Minuteman
Sep 15, 2011
204
3
California
#1
Hi there,

I mounted a PST 6-24X in a pair Burris Xtreme Tactical rings on a Howa 308. The gun came with a EGW 0 MOA base. After sighting in at 100yd, there is only 5.5 mil left going up in elevation, about 14.5 mil left going down.
frown.gif


I checked the EGW base and believe it is mounted properly, with lower end pointing to the muzzle direction.

I thought the scope will be approximately in the middle of elevation adjustment range after sighting in. What went wrong? Any suggestion on how to rectify the problem?

Thanks,
Kevin
 
#2
Re: One 5.5 mil left after sight in

Not sure how the zero stop turrets work on these but on some scopes there is a certain range you can dial. Could this be an issue?
 
#5
Re: One 5.5 mil left after sight in

In my experience there are two factors that affect your zero: the "mechanical zero" of the scope itself (i.e. where zero really is vs what is marked on the turret), and the rifle, barrel, rail/mount, receiver etc of the rifle.

I have had two different AR uppers that were 10 MOA apart with the exact same scope (one was 5.56mm and the other a 6.8). It annoyed me, but I lived with it.

If you aren't hanging anything off your barrel, I think the 20 moa base/mount is a good idea to get more elevation.
 
#6
Re: One 5.5 mil left after sight in

Also, you might consider higher quality rings that are sold in serialized pairs (Seekins is an example--the rings are made from same bar of aluminum then separated at birth, if you will.) These will be well matched to each other. No offense to Burris Xtreme...they seem pretty popular.
 
#7
Re: One 5.5 mil left after sight in

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Recon5x5</div><div class="ubbcode-body">In my experience there are two factors that affect your zero: the "mechanical zero" of the scope itself (i.e. where zero really is vs what is marked on the turret), and the rifle, barrel, rail/mount, receiver etc of the rifle.

I have had two different AR uppers that were 10 MOA apart with the exact same scope (one was 5.56mm and the other a 6.8). It annoyed me, but I lived with it.

If you aren't hanging anything off your barrel, I think the 20 moa base/mount is a good idea to get more elevation.
</div></div>

Thanks, good explanation.

Is there any chance my scope base out of spec? If I swap the rings front and back would it help?
 
#8
Re: One 5.5 mil left after sight in

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DFOOSKING</div><div class="ubbcode-body">I'd say that is the luck of the draw on your setup.

There's nothing else you can do if your setup isnt limited by the zero stop shims. Except maybe shimming the base which is stupid.

Go get the base. </div></div>

Thanks. I am going to buy a 20 MOA base, just not sure if I will buy EGW and Burris again.

I also have a Win M70 with Weaver 3-15X50 Tactical on Burris XTR rings and EGW 20MOA base, again. After sighting in at 100yd, I have 16.5 mil left. I thought I would have 29mil/2 + 20/3.438 = 20 mil left. So 3.5 MIL is lost in the setup. In other words, I only gain 2.5 mil by using a 20 MOA base (5.81 mil). My friend's TPS base and ring on M700 give him precisely 20 MOA advantage.

Why does it happen to me twice on two different guns? Was it my bad luck or the EGW and Burris combo?
 
#9
Re: One 5.5 mil left after sight in

It looks like I have to pay. But for Howa short action, there is very limited options available in terms of scope base. I know EGW makes a HD 20 MOA base.

If it is indeed my gun cause this lost of 4.5 mil elevation, then adding a 20MOA base barely makes up for it. I have to use Burris Signature Zee rings on top of a 20 MOA base. Hoping the posi-align offset inserts help me to gain more elevation.
 
#10
Re: One 5.5 mil left after sight in

I have no idea what "posi-align" is, but it sounds like ever more complexity.

When you put a rail (I assume that is what the EGW thingy is) on top of your Howa, you raise the scope further above the bore. All other things equal, this will cause you to shoot LOW, which will require you dial UP. This alone might explain your issue. (My experience with other EGW parts is they tend to be thick and sturdy. Thick in this case means higher above the bore.)

I'm no expert, but why not just get rings and mount right on your receiver? This is a very solid way to go. A little lock-tite and you will hold zero for a generation. If you then need more elevation than your scope travel allows, you can also use your reticle for holdover.

Just a thought...
 
#12
Re: One 5.5 mil left after sight in

Posi-align are some plastic inserts that go between scope rings and scope. By changing them you can gain or loss elevation. It works like a canted scope rail, but more complicated.

The EGW 0 MOA on my Howa is a rail. It is pretty thick, may be 0.5". I have Burris XTR low rings (0.25") on top of them. Do you think this can cause loss of 5.5 MIL?

I still prefers one piece rail than Leupold standard base. I can buy canted rail such as 20 MOA ones, and it is easy to install or change scope and rings.
 
#15
Re: One 5.5 mil left after sight in

I'm pretty certain the higher your scope goes, the more you lose elevation travel. You could draw it out on a piece of paper and demonstrate it to yourself.

I understand the convenience of the rail. Skip the posi-align. You've already got low rings. Assuming your cheek weld is how you like it with a base, get a 20 moa base.

My 2c...

[edit] Actually, the geometry of scope height over bore should only make just that difference, right? I am confusing myself now. For sure, a very small angle in the rail itself would make a large difference at 100 yds. Try turning the rail around the other way and see if that changes anything before spending more $$$.

 
#16
Re: One 5.5 mil left after sight in

I did the math

1. On m70 with EGW 20 MOA rail and Burris XTR rings, I have 16.5 mil left in the Weaver 3-15X50, versus 20.34 mil (29 mil/2 + 20/3.438). This means the EGW 20 MOA and Burris combo take about 3.84 mil.

2. On Howa 308 with EGW 0 MOA rail and Burris XTR rings, I have 5.5 mil left, vesus 10 mil (20 mil/2), which says EGW 0 MOA and Burris XTR combo takes 4.5 mil.

3.84 mil vs 4.5 mil, I guess it is possible. I am definite on the market for a 20 MOA base. Does anybody know if Burris Signature Zee works well with EGW 20 MOA HD rail or not?
 
#18
Re: One 5.5 mil left after sight in

Tolerance stacking , every rifle is different . Is the top of the receiver flat and parallel to the bore ? Are the threads on the barrel parallel to the bore ? Are the treads in the receiver parallel to the top of the receiver and the bore ? Is the bore straight and is it clocked so as to give a minimal deviation from the centerline ? All of these affect the departure angle of the bullet and the angular relationship with the sighting device .

The short answer with an OEM rifle to one or more of these questions is no it isn't and barring rebuilding / trueing the gun pick the base that gives the elevation desired and drive on . Z rings have no place on a precision rifle , if you want to go cheap stick with the extreme rings .
 
#19
Re: One 5.5 mil left after sight in

Ouch. I don't know. Perhaps other Howa 308 Varminter user can chime in with his scope setup. So we can compare notes and see sample variation.

Can you explain why Z rings are not good on precision rifle? I thought if I take the time to remove oil on the rings and plastic inserts, they should hold the scope fine on a heavy barrel 308. No?
 
#20
Re: One 5.5 mil left after sight in

Plastic inserts , these rings are designed for the hunting market where the accuracy demands are way less stringent than on a good precision rifle .
The EGW bases and Burris XTR rings are both good products for the money . There are tons of reasons that the magic number of elevation available isn't what it should be and they all revolve around anything man made can and will screw up at some time . Was the elevation travel ever verified by shooting or a collimator to be what they advertised , Most often it isn't .
 
#21
Re: Only 5.5 mil left after sight in

Kevin,

Have you actually shot the gun to zero it or was it just a bore sight?

First I would take everything apart and remount. Check to make sure that your base does not need to be bedded by just putting in the front screw until it snugs and doing a "piano key" test to the back of the base. It should not move. Repeat with the front. If the base moves when you do this, you will need to bed your base with epoxy. A 20 moa base would be nice, depending on how far you want to shoot, but should not be the cause of this issue.

Secondly, as others have stated, I would invest in some new rings. I run Seekins and don't think they can be beat, just my opinion.

With the scope I would count the number of total clicks that you have and then divide by two. Do the same for windage. After turning the turrets down all the way, adjust to the number that you got when you divided by two. That should get you to your mechanical zero. You can check that by placing the objective against a mirror and rotating the scope back and forth, making sure that the crosshair center does not move when rotated. Now mount the scope and see where you are with a bore sighting. With a 0 moa base you should be fairly close. Record the number of clicks that you have to move to get a pretty good bore sight. Add this to the number you have gotten by dividing total number of clicks by two. Now set your turret cap to your bore sighted zero and see what you have left for elevation. It should be pretty close to 10 with the scope you have. If not, something is way out of alignment and you need to address that. If it is roughly in the middle of your total mils, go out and shoot it and see where you are. If you shoot it after your bore sight and still need to come up on elevation considerably, there is something wrong with your rifle that needs to be corrected (action trued, new barrel, rifling run out, etc.)

By starting over and looking at one piece of the puzzle at a time, you should be able to diagnose this problem a bit easier.

Hope this helps, sorry I didn't catch this thread earlier.

Tom
 
#22
Re: Only 5.5 mil left after sight in

From personal experience those Burris Signature rings hold the scope really well...The picattinney base not so much! And I honestly hate the XTR rings! I would suggest you look into quality rings. Such as TPS, Seekins, Badger, Aadland, or something like them.
 
#23
Re: Only 5.5 mil left after sight in

The scope was sighted in at 100yd. The base mounts flush on the gun, so do the rings on the base.

I could swap the front and back rings to see if it is a problem with the Burris XTR. But other than that, I am not sure what else could be tried.
 
#24
Re: Only 5.5 mil left after sight in

Your making this too complicated . Obviously a 0 MOA base isn't going to give the elevation travel that You want because You've shot it and there isn't enough left . Get a base with cant built in , from what Your saying at least 20 more likely 30 MOA , and get back to shooting .
 
#25
Re: Only 5.5 mil left after sight in

Kevin, I had the same issue with my Savage 10 and a Valdada IOR scope. It took a 30 moa base to get me to where I wanted the scope set. My scope also had 20 mils total adjustment. Burris XTR and EGW base.
 
#28
Re: Only 5.5 mil left after sight in

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: coug</div><div class="ubbcode-body">put a 20 MOA base on it .... I say no more. </div></div>

^^^this or buy a Razor. I got 29.4 mils in elevation left after zeroing. I could probably lob a .22 out to 600 yards or so.
grin.gif
Just get the rail. EGW makes good shit. Put some Seekins/Vortex rings on it and have a beer.
 
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