Scope mounting and Zeroing

[DDMS]

Hi guys, I’m looking for some advice.

I am trying to zero my rifle/scope however even with the wind age adjustment fully right, my rounds are landing 2” left of centre at 100yards.

Vertical adjustment is ok.

I have a Zeiss Duralyt 3-12x50, mounted with Tier one medium mounts on a weaver/Picatinny rail. The scope rings are torqued as per Tier one instructions.

Group size is currently just over 1 MOA, but, these were taken with a hot barrel tonight as I was running out of time before I needed to get home. I already know this shoots better than that so accuracy isn’t in question.

what should I be checking for scope alignment?

Thanks

 

[09mutley05]

Undo the rings, turn the bottom half 180 degrees and re tighten, sounds like they are sitting of centre. Hopefully this will sort things out for you.

 

[DavyG]

Try swapping the front/rear mount. Is the rail fitted or machined?
DG

 

[DDMS]

Try swapping the front/rear mount. Is the rail fitted or machined?
DG

It’s a bolt on rails which again is torqued and Loctited in place.

 

[DDMS]

Undo the rings, turn the bottom half 180 degrees and re tighten, sounds like they are sitting of centre. Hopefully this will sort things out for you.

There is a level bubble on one of the mounts so if I turn this I won’t be able to see. Will try turning one at a time.

 

[09mutley05]

Dwhats the make and model of the rifle?

 

[DDMS]

BSA Monarch in .243

 

[09mutley05]

If it were me I would try the rings above, as I said earlier, if that make no difference can the rail be turned around? Try that. If that’s no good have you got another scope you could try? I doubt it’s the scope as said earlier it sounds like something is off centre to the bore either rings or rail would be my guess.

 

[User00040]

A few suggestions,

1. The BSA Monarch is a dovetail equipped action, any reason why you are using a pic rail and not a scope mount that clamps directly onto the dovetail?

I suspect you are getting some tolerance stack through components as mentioned above.

2. Acquire some 30mm diameter roundbar (assuming your scope has a 30mm tube) and mount it in just one ring. Have a look to see if it is skewed away from the bore. If not excessive you could lap the rings although this would make them unsaleable afterwards for use on another rifle.

3. Check you parallax/cheek weld. The BSA Monarch has a slight raised comb and while these are beneficial they can also contribute to a parallax error (i.e not looking directly through the scope).

4. The other option is to buy a one piece mount that fits the dovetail directly (19mm I believe) and check alignment.

 

[jcampbellsmith]

Try these adjustable rings Burris Signature Zee Weaver 30mm Medium Scope Rings
Regards
JCS

 

[DDMS]

A few suggestions,

1. The BSA Monarch is a dovetail equipped action, any reason why you are using a pic rail and not a scope mount that clamps directly onto the dovetail?

I suspect you are getting some tolerance stack through components as mentioned above.

2. Acquire some 30mm diameter roundbar (assuming your scope has a 30mm tube) and mount it in just one ring. Have a look to see if it is skewed away from the bore. If not excessive you could lap the rings although this would make them unsaleable afterwards for use on another rifle.

3. Check you parallax/cheek weld. The BSA Monarch has a slight raised comb and while these are beneficial they can also contribute to a parallax error (i.e not looking directly through the scope).

4. The other option is to buy a one piece mount that fits the dovetail directly (19mm I believe) and check alignment.

The monarch doesn’t have a dovetail. The serial number on mine is definitely a monarch and is tapped for a rail. It came with weaver mounts but I have fitted the rail as the scope I have purchased couldn’t achieve the eye relief I needed with them.

I have added a comb raiser to get the correct eye height/alignment and am happy that this is correct.

I have just stripped it down and notes two things. The front top portion of the scope mount wasnot equally spaced when torqued. Ie one side was further round than the other. Also when I have loosened the mount of the Picatinny I think it may have moved from off centre.

after taking it all apart and religiously following the mount instructions I will try again. If this doesn’t work I have another scope I can try which I had zeroes on this rifle originally. I am suspecting this May have been user error. Ie: I nicked it up.

 

[DDMS]

Try these adjustable rings Burris Signature Zee Weaver 30mm Medium Scope Rings
Regards
JCS

They may be worth a go of I can’t get it this time. Either that or I will get someone else to try.

 

[DDMS]

I am also going to try without the moderator on.

 

[User00040]

Sorry, confused it with another BSA.

Did you push the mounts forward slightly before tightening them on the picatinny rail?

 

[09mutley05]

Is this a set to you? change one thing at a time! Take your time let your barrel cool down, maybe take a flask with you, been in your situation before, you can end up going round in circles or worse that you started. Before you know it you can waste a box of ammo and be none the wiser.

 

[aled24]

I had the same problem a few years ago, it was the scope internals that was faulty.

 

[8x57]

BSA Monarch in .243

If it's a Monarch without the integral dovetail it's presumably post 1968 which originally would have been drilled and tapped for separate weaver bases.
You're causing me a slight bit of confusion understanding the possible problem because you mention Tier One mounts when you actually mean rings which are attached to a one piece Picatinny rail that has been fitted to the rifle in place of the original separate Weaver bases?

 

[Eric the Red]

I have a set of Millet 30mm low windage adjustable picatinny mounts NIP you can have for £30 posted

 

[DDMS]

If it's a Monarch without the integral dovetail it's presumably post 1968 which originally would have been drilled and tapped for separate weaver bases.
You're causing me a slight bit of confusion understanding the possible problem because you mention Tier One mounts when you actually mean rings which are attached to a one piece Picatinny rail that has been fitted to the rifle in place of the original separate Weaver bases?

Yes sorry. Tier one rings on a one piece rail. This is attached to the original drilled and tapped holes for the weaver bases.

 

[8x57]

I would be inclined to go on the lines of assuming that there is no fault with the Tier One rings as the company has an excellent reputation and you hear very few complaints about their products. Then assuming that the Picatinny rail is also of good quality and not some cheap poor quality knock off that isn't straight and true I would be looking to see that I have attached the rings to the rail correctly.
That then only leaves the questions as to whether the picatinny rail has been fixed in true alignment to the bore or the question regarding the actual scope.

ejd gave a good write up about his method of ensuring the picatinny is correctly aligned and secured to the receiver some time back. It may be worth having a look to see if you can find it.
I suppose it is possible that the original mounting holes in the rifle receiver may not be perfectly aligned with the bore. It's not unheard of, Browning having a particular problem with this with the first rifles in the X-Bolt range.

It should be easy to rule out the scope by mounting and testing another scope of known quality and reliability. If the replacement scope zeroes and is still pretty much centred in it's adjustment range you will then know that the problem lies with your Duralyt scope.
Incidentally I've read several reports on this site of similar problems with this particular model of scope over a number of years so its not totally inconceivable that there may be a problem with the scope but I think you need to rule out all other possibilities first.