Gentlemen,
I have afforded something that I have had in mind for quite a time: a Heckler&Koch MR223. Being a friend of good material, I had the gunsmith mount a Schmidt&Bender 1-8x24 EXOS scope on a cantilever mount by ERATAC. So only high quality components have been used.

But the first trip to the range was a puzzling experience. 5 rounds at 100 metres with a 6 o'clock hold, no hit. At 50 metres, 5 shots with a 6 o'clock hold, again no hits. Then I started POA counterclockwise along the outer edge of the target, start at the bottom of the target in the middle, 1 shot each at 6, 3, 12 and then 11 o'clock, at the 11 o'clock a hit on the 1 o'clock position near the edge of the target. 6 o'clock hold again after 40 (!) clicks to the left, POI 6 rounds position at 5 o'clock. Elevation ok, but lateral adjustment to the left is at the usable end (red area on the scope's adjustment turret).

Iron sights gave me POI dead on in the centre at 50 metres. See picture.

When I checked the scope I found the tube to be slightly canted to the right. Could a noticeable, but not very strong canting cause a deviation of about 16" at 50 metres?

Of course gunsmith doesn't believe me and says he has everything exactly aligned. Says might be the scope. I don't believe it, but you'll never know.

Any input appreciated

Regards from Germany
Ulrich


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Life is too short to own a bad gun

Well, let's look at the math for a moment and see if we can answer that.
you are saying the scope is off 16" at 50M, so let's get our units aligned first and since I'm in the USA, I'm going to convert the meters to feet rather than the inches to meters.
So, 50M ~ 164'
I don't know how far apart the front mount is from the back mount of your optic, but let's assume 6" for the sake of our math.
You multiply the error of the mount by the distance the bullet travels. That is to say, canting the optic .001" gives you a .002" error every foot.
So, for your error, take the error and divide by the 16" by (164 *2) and you get a .049" error in that 6" of mounting distance being needed for 16" of error.
Summary, a bit over 1.2mm in the scope base and you are that far off if that base is 6" long.
If the base is shorter, the distance is commensurately shorter. You don't specify which mount you have, but several of them look more like 4" in length, so the error needed across the mount becomes .032" ~ .8mm

I hope this helps.

I have a similar problem on my 308 long range rifle. After I installed a scope and zeroed the POI at 100 yards (91meters +/-) I only had 1 Minute of angle adjustment remaining to the Left (8 clicks) I used aluminum beverage can shims (approx. .008" thick). I used 3 thicknesses on the front ring's right side and 2 thicknesses on the rear ring's left side. On my scope this moved the POI 80 MOA or 80" to the right and when I re-zeroed the scope, the cross hair was almost perfectly centered.

I learned a very long time ago to never trust mathematical calculations to others! Gunsmiths are only human and often make mistakes, but seldom admit to them!

On you base, there MAY be some set screws for making vertical and horizontal adjustments. If there are they will need to be permanently locked into place after adjustments are final!

For long range scopes I like my bases to have a 40 MOA tapper, and have paid for 40 MOA, but often receive a 20 MOA taper.

Keep an eye on the Thousandths of an inch and the yards will take care of themselves!

Ivan

@teletech

thanks for your explanation and help. I'm not good in mathematics, but I understand that 16" of error to the right might be possible if there is a deviation in the mount.

Not sure if I explained it right, I'm no native speaker. It is obviously not the mount that is canted, but the tube of the scope is twisted/canted within the mounting rings. Distance between the flat turret upper side of the elevation turret to the mount base is 2mm less on the right side than on the left side. Don't know how many degress of cant this might be. Looking through the scope without magnification (1x) and flipped up front sight I can clearly see the front sight right of the reticle when the gun is straightly aligned on a solid surface.

I'm sorry if my wording is a bit awkward and unclear.

regards
Ulrich

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Life is too short to own a bad gun

No need to apologize, I understood that there was something of a language gap and also that it's very challenging to diagnose a gun problem with just words compared to being there in the best of conditions.

Any chance you could post pictures of the mounted scope, ideally showing the cant of the scope or rings?

The turret being canted slightly to the right isn't going to throw the scope off center. It will make the adjustments slightly off as a correction right to left is also going to move the point of impact slightly up/down.

Unless the scope tube is bent, I'd strongly suspect that either the scope mount is bent, all the mounting holes aren't on center or the scope mount screw holes on the rifle aren't on center of the bore. The point above about possible windage adjustments in the base may be possible. Check with manufacturer?

Over here, we generally fire our first shots at 25 yards/meters to make sure we're on paper and adjust the sight to get shots at longer range on paper.

sorry for the picture, but it is very difficult to get everything aligned with the camera focus. You can see at the position of the ruler that the tube is slightly canted.

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Ah, that cant... nope, no chance of that throwing you off 16" at any reasonable distance. You have some other (and pretty serious) issue going on.

The rail on the HK is very unlikely to be the issue considering it's construction. My advice is to get another scope and mount, it can be a really cheap set, and try it out. That should isolate the optic system from the rifle. Then assuming it's the optic system, mount the good scope in the cheap mount and cheap scope in the good mount to isolate the problem further.

well, I swapped the scope and mount with a shooting buddy who has exactly the same gun. His POI was right too, mine with his scope/mount was where his gun had POI with that combo. So no problem with the HK. Now the scope swap would be the next step. Not an easy task as the gunsmith obviously used some glue to additionally fix the tube in the mount.

BTW: I managed to sight in the scope at 100 meters. There is still about 40 clicks to the left possible, but the adjustment display is in the red area. Schmidt&Bender said, this should not necessarily be a problem. I'll contact them again with the exact setting of the scope.

regards
Ulrich

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