Misaligned scope mount dovetails on new Sako 85 Finnlights

[stonecreek]

"Sako TAPERED Dovetails".

They are tapered for a reason -- to assure that the recoil of the rifle when fired tends to make the scope mounts/bases tighter rather than tend to loosen them. This is a clever system which is unique to Sako (a few other manufacturers used integral dovetails, but they utilized cross pins or other mechanisms to keep the scope from drifting forward under recoil.)

However, the tapering has one drawback: If the scope mount has one fixed claw (usually on the left side like Optilocks, Leupolds, etc.), then as the mount is positioned further forward on the dovetail the ring moves further to the left. If the front and rear rings are not positioned relatively close to the same place (fore and aft) on each dovetail, then the scope will point slightly left or right of the bore.

If in boresighting with the scope near its mid-range of adjustment the scope is pointing left, then this can be cured by either moving the rear ring forward or the front ring rearward (whichever is more practical). The opposite movement will compensate for a right-pointing scope.

In some applications, like a short scope on a long action, the latitude for movement of the rings may not be sufficient. If another type of ring which doesn't feature this problem (Millett, original Sako, Redfield, etc.) can't be substituted, then the proper ring (front or rear, according to which way the scope is off) can be modified with a three-corner file by slightly widening its clamp groove. This will have the same effect as "moving" that particular ring rearward, so be sure which way it is that you want your scope to move.

Having never seen the vertical mismatch problem that David started this thread about, I've never needed to compensate in the vertical plane (other than for a set of uneven Redfield-type bases I mentioned earlier, that problem being resolved with aluminum shims between the scope tube and ring). But another way to "fix" it would be to simply machine the ring clamp base above the clamp for the "high" dovetail a little shorter (deeper), thus allowing the clamps to reach a little deeper. There would be a practical limit to how much you could "gain" in this manner, but it would probably be sufficient to bring the mounts into reasonable alignment.

 

[NO85CL]

"Sako TAPERED Dovetails".

Having never seen the vertical mismatch problem that David started this thread about, I've never needed to compensate in the vertical plane (other than for a set of uneven Redfield-type bases I mentioned earlier, that problem being resolved with aluminum shims between the scope tube and ring). But another way to "fix" it would be to simply machine the ring clamp base above the clamp for the "high" dovetail a little shorter (deeper), thus allowing the clamps to reach a little deeper. There would be a practical limit to how much you could "gain" in this manner, but it would probably be sufficient to bring the mounts into reasonable alignment.

Like I said in my reply to David, moving the ring forward tightens it up and holds it down to the base as well as centering it horizontally! (in his first comments he writes about the space between the base and the rings, a thing I also noticed and that space disappeared when I pressed the ring to fit the dovetail by moving the ring forward (the forward one)) All equal with the back ring, in my case moving the front ring only meant a difference of distance compensation for 200 mtrs on the ASV+ ring 7 (in other words in the vertical plane). At least 10 clicks down that I can use for flexibility upwards!
My rear Optilock ring by the way cannot be moved forward due to a pin that fits in the rear base, and holds it in place and centered. Therefore adjustments in my case had to be made by moving the forward ring only.
But, no machining, no waiting for the gunsmith

 

[David_S]

Further considerations

I've been off hunting, it being spring here, so have only just returned to the thread. Incidentally, the 260 dropped 2 deer at 400yds and 25 degrees up in quick succession with single shots so my "epoxy fix" seems to be working.

Some observations on recent posts.

Stonecreek, all the one piece Optilock ringmounts I have seen have the fixed clamp and torx screw on the right hand (bolt) side so that moving the mount forward on the front taper moves the scope to the right and therefore the POI to the left. (Edit. Oops! My mistake. I have just realised Stonecreek is right. The fixed claw is on the left so moving the mount forward moves the scope to the left and the POI to the right.) One of my photos shows this. I don't consider this movement a drawback but a neat way of adjusting the scope lateral alignment.

Your suggestion of shimming between the scope and the rings does work as I tried it but it was not really satisfactory as it required 0.8mm of shims which is excessive. I was also concerned about uneven pressure on the (expensive) scope tube from the shims. And yes, removing metal from the dovetail groove, or the clamp, would work but I was reluctant to experiment on a new rifle in this way. And in any case the epoxy method appears to be working.

NO85CL Interesting that you have encountered the same problem - that makes four separate instances with the 85 noted on this forum, so it looks as if it may not be uncommon. I wonder how many scopes mounted on 85's with one-piece ringmounts have the scope reticle adjustment almost maxed out without the owner being aware of the fact. I know that whilst I waited for the Swarovski to arrive I used an old Leupold in the interim, and was only vaguely aware there was a problem but did not worry as the rifle shot well and the arrangement was only temporary.

Your fix is also interesting but can only work if the front dovetail grooves are sloping downwards so that sliding the mount forward lowers the front of the scope relative to the bore. This seems to be the case with your rifle as the gap between the ringmount and the flat top of the dovetail disappeared as you slid the mount forward. On both my 85s the front and rear dovetail grooves are parallel, though offset vertically. Even if the groove was angled downwards, moving the front ring would affect both the lateral and vertical scope alignment. It appears that in your case one position fixed both your lateral and vertical misalignment but I would regard this as a fortuitous coincidence. In my case I positioned the front mount so that the scope lateral adjustment was zero, which still left the rifle shooting way too low.

As I have mentioned earlier my 75 Finnlight with the identical dovetail arrangement has no vertical alignment problem, so I suspect this is a manufacturing defect with the 85 action or a batch of them. When I have a moment I will write to Beretta (NZ) so they are aware of the problem.

David

 

[paulsonconstruction]

Like I said in my reply to David, moving the ring forward tightens it up and holds it down to the base as well as centering it horizontally! (in his first comments he writes about the space between the base and the rings, a thing I also noticed and that space disappeared when I pressed the ring to fit the dovetail by moving the ring forward (the forward one)) All equal with the back ring, in my case moving the front ring only meant a difference of distance compensation for 200 mtrs on the ASV+ ring 7 (in other words in the vertical plane). At least 10 clicks down that I can use for flexibility upwards!My rear Optilock ring by the way cannot be moved forward due to a pin that fits in the rear base, and holds it in place and centered. Therefore adjustments in my case had to be made by moving the forward ring only. But, no machining, no waiting for the gunsmith

Grind the pin off and you can put the rear ringmount anywhere you want. The pin is redundant & superfluous & serves no function with regard to scope mounting. Leopold ringmounts come with NO pin for that very reason & allow more flexibility. There is no reason to allow the "pin" to limit what scope you use or what eye relief you need or to limit any lateral adjustment you may need to make. That "pin" is a carry over from a by gone age that I don't think the designer can even explain, except that it made him feel better. None of my scopes are mounted on Sakos with the "pin" & they perform flawlessly. If I used ringmounts with the "pin" none of my scopes would be able to be mounted with proper eye relief. The "pin" does not hold anything in place & centers nothing, as the pin is much narrower than the slot in the dovetail & the tapered dovetails actually cause the scope mounts to become tighter under recoil forces, which the "pin" actually prevents. This "pin" thing & it's "need" is one of those things that should be put to death, as it messes up a lot of scope mounting unnecessarily in my opinion.

 

[David_S]

Grind the pin off and you can put the rear ringmount anywhere you want. The pin is redundant & superfluous & serves no function with regard to scope mounting........

That's interesting. I could never fathom the purpose of the pin - I assumed it was just a case of belt and braces. I don't think you need to grind off the pin. I am not absolutely certain without removing the scope (which I don't really want to do) but from memory I think the pin can just be tapped out with a suitable drift. David

 

[NO85CL]

I've been off hunting, it being spring here, so have only just returned to the thread. Incidentally, the 260 dropped 2 deer at 400yds and 25 degrees up in quick succession with single shots so my "epoxy fix" seems to be working.

NO85CL Interesting that you have encountered the same problem - that makes four separate instances with the 85 noted on this forum, so it looks as if it may not be uncommon.

Your fix is also interesting but can only work if the front dovetail grooves are sloping downwards so that sliding the mount forward lowers the front of the scope relative to the bore. This seems to be the case with your rifle as the gap between the ringmount and the flat top of the dovetail disappeared as you slid the mount forward. On both my 85s the front and rear dovetail grooves are parallel, though offset vertically. Even if the groove was angled downwards, moving the front ring would affect both the lateral and vertical scope alignment. It appears that in your case one position fixed both your lateral and vertical misalignment but I would regard this as a fortuitous coincidence.

David

Hi David.
I may well have been a bit unclear, and I may also be proven wrong, but I still think that the dovetails probably are OK. It may not be a perfect fail-safe set up, but I still think the mounting job is the main problem. Since, by design, the aft end of the forward base plate is smaller than the width of the ring shoe (by a few millimeters), there is slack at that point (you did not say whether you, like me, also mounted the scope ring at the back end of the forward dove tail!). Even with perfectly aligned grooves, the shoe on the ring and the base plate will not have a firm and stable fit if they are not exactly the same width! Where the plate is smaller, it would be the shoe's screw, with its small plate, that keeps the shoe in place. By design, the whole point with the dovetails, is that they do not have the same width everywhere. The ring shoe only fits the base plate perfectly at a given point. The problem with the slack is that, as you tighten the mounting screw, a small plate attached to the screw is pushed inwards, which pushes the ring shoe to the side and potentially upwards a bit. Best case, if you keep it well down when tightening the screw, you will be able to secure the shoe down in the groove where it should be (although the right hand side, the side with the screw, only will be held in place by the screw and its little plate, rather than the side of the shoe itself). Worst case though, it will have been pulled up and tightened in the wrong place, still in the groove, but too high. I undid the screw enough so that the small plate attached to the screw, and the rest of the mounting shoe were aligned. Then I pushed the shoe all the way until it was stuck on the base. Only then I tightened the screw.
So, in other words, I do not think that the rifle was constructed the wrong way or with a slight imperfection, I do not think either that Sako´s forward dove tail slope down differently, I just think it was not mounted the way it is intended, at least in my case.

It is a pity there is no possibility for questions and answers directly to Sako, on Sako´s site.

Having said all this, I have not shot 2 deer with it yet, so it all remains to be seen. Sounds like you had a good hunt, which is the most important thing

 

[David_S]

NO85CL, I have read your post carefully and am pretty sure I can follow what you are saying, but it still does not make total sense to me. Unfortunately I have just sighted-in both my 85 Finnlights at 200yds so am reluctant to remove the scope on either to test what you suggest, but I have had a good look at the 260 mounts and reread the Sako Mounting instructions for the Optilocks which are reasonably clear. My comments follow.

I still think that the dovetails probably are OK

But not in my case. As I said in an earlier post the rings effectively sit on the lower edge of the dovetail groove. Front and rear dovetail grooves are parallel but offset vertically by 0.8mm. Moving the front ring forwards or back does nothing to eliminate this 0.8mm gap and, incidentally, the small gap between the top of the dovetails and the bottom of the mount does not alter on my rifles when I move the mount.

By design, the whole point with the dovetails, is that they do not have the same width everywhere

Yes, as Stonecreek has pointed out the tapered dovetails are an anti-recoil locking device as well as a means of effecting lateral adjustment.

Sako's mounting instructions read,

The mount is assembled on the dovetail of the receiver by means of a wedgelike locking piece (C) and mounting screw (D)... The recoil stop (pin A) of the rear mount should fit firmly into the recoil stop groove built into the rear of the receiver bridge.
The front mount should be approximately in the middle of the front mounting rail. Notice that each move of 1mm forward alters the point of impact 25-30mm right at 100m.....The front mount should be moved if the windage adjustment of the scope is not enough.

you did not say whether you, like me, also mounted the scope ring at the back end of the forward dove tail!

No, I followed the Sako instructions and mounted the rear ring with the pin up against the recoil stop groove and the front ring in the location where no scope windage adjustment was required. This is a little in front of the mid position as can be seen in my earlier photos.

I undid the screw enough so that the small plate attached to the screw, and the rest of the mounting shoe were aligned. Then I pushed the shoe all the way until it was stuck on the base. Only then I tightened the screw.

Undoubtedly this will give the strongest mounting but according to Sako's instructions it is not apparently the way it was designed. I think you were lucky that on your rifle this position coincided with zero lateral scope adjustment.

What I would be interested to know is whether the front dovetail grooves on your receiver align vertically with the rear dovetail grooves or whether they do not as on both my 85s. If your scope when zeroed at your zero range of 100, 200m or whatever is close to the midrange of the scopes vertical adjustment as you indicate then I think you will find your dovetails are in close alignment.

Having said all this, I have not shot 2 deer with it yet, so it all remains to be seen. Sounds like you had a good hunt, which is the most important thing

You are quite right. These are hunting rifles not safe ornaments, and it is far better to be out hunting than cursing scope mounts! And yes it was a good hunt. The 260Rem took 2 chamois and 2 deer, and the 270WSM 1 deer and 1 pig. Had to make three 3hr trips to pack it out. Phew! Last week we went back to the same area, saw heaps of fresh sign but no animals at all except one deer on the 4wd track on the way out. That's hunting I guess. It was a wise hunter who when asked by a novice where to find deer replied, "Deer are where you find them!"

David

 

[David_S]

Well, I have just collected a new Sako 85 Finnlight in 260 Rem courtesy of Beretta NZ. They never actually said why they were replacing my original rifle but it can only have been the dovetail problem. The new rifle appears to have perfectly aligned mounts.

My local dealer told me that it is the first time in the 11 years he has been in business that he has heard of Beretta replacing a rifle! I am not, however, pushing the issue on my 270 WSM as it is shooting well and the misalignment was not nearly as pronounced as the 260.

So thank you Beretta.

David

PS Paulsonconstruction, (Post #17) you can donate the dollar you owe me to your favourite charity!

 

[emmerth]

David,

Thanks for the update and glad to know that Beretta is standing behind their product. Unlike the issues that I am with a Nissan truck. But, that is another story and not appropriate for the this site. ound1:

 

[topgear]

Hi David

Full marks to Beretta NZ. That's the sort of service they should be offering for sako owners. I'm glad they have 'fixed'' the problem in the correct manner. Let them know you have let everyone on here know how upstanding they have been and maybe push your luck for a free baseball cap!

Cheers John

P.S. Can we now please get some more pictures of you and your new sako in that beautiful countryside of NZ knocking over a few tahr, chamois and deer please !

 

[David_S]

Replacement 260 is looking good

Hi David John

P.S. Can we now please get some more pictures of you and your new sako in that beautiful countryside of NZ knocking over a few tahr, chamois and deer please !

Have to sight the new rifle in first. Bore sighted it today. With my epoxy ring insert (my "fix") removed from the rear mount the scope only needed a slight horizontal adjustment and no vertical adjustment, so things are looking good. As soon as the weather clears will sight it in. At the same time I am going to try 140gr Hornady A-Max rather than the 129gr SSTs I have been using up to now in my M995 and earlier 260Rem. I hope to get better longer range performance.

Here is the new setup. Seems almost a shame to get it dirty!

This time I have put a couple of strips of auto electrical "loom" tape alongside the magazine to protect the "soft touch" coating. The coating was starting to flake off due, I think, to rubbing against my side when being carried by the sling over my shoulder as I do frequently. The matt black loom tape blends in perfectly with the stock and does not seem to shrink over time as ordinary electrical tape tends to. You can't even see it in the photo.

As for pictures I hope to get some more when I go after tahr in late May or June. And before the weather gets much colder I am planning a short local "tops" trip for chamois and deer or just photos. However from now on the weather can be dodgy. (Actually in NZ it can be dodgy at any time of year.) For example it can change from this

to this overnight

David

 

[topgear]

Looks good David. Perfect scope clearance. What sort of range will you shoot out to with that combo?

 

[David_S]

Looks good David. Perfect scope clearance. What sort of range will you shoot out to with that combo?

Our typical shot is 200-300 yards but we hope to extend that to 500. Maximum kill with the previous 260 was a deer at 425yds so 500 should be achievable but effectiveness will depend on bullet performance which is why we are going to try the A-Max. - David

 

[Fallman]

All,
I just upgraded my scope to a Swarovski on my Mod. 85 Finnlight (rifle purchased in 2010) and have the same problem as this thread. The Gunsmith is a Beretta and Swaro dealer and could not believe that boresighting used virtually all of the elevation adjustment, which is no good as I had a Balistic Turret. So they mounted 4 different scopes 2 with 30mm tubes and 2 with 1" tubes. Each mount used a different set of rings. All 4 mountings behaved exactly the same and used virtually all of the adjustments. The gunsmith said that the problem is with the rifle and will be contacting Beretta in the morning. This is really disappointing. The previous scope was a Zeiss with the Z800 and I had problems getting it sighted but thought is was me. But once sighted in no further adjustments were ever needed. Ill let everybody know what the factory has to say, but the factory authorized warranty place believes the rifle has issues.

 

[David_S]

Fallman, that is very interesting. It looks as if mine were not isolated problems. What action / calibre is your Finnlight? Mine are the S (260) and SM (270 WSM).

I will be interested to hear how your gunsmith gets on with Beretta. However if he has no satisfactory response try my epoxy fix which is quick and effective once you have the custom grinding tool. Your gunsmith should be able to fabricate one without difficulty - might generate a lot of new work for him!

It is well worth the effort getting the Swarovski BT scope mounted properly as I really like the BT system, not to mention the clarity of the glass. I now have Z3 scopes mounted on both my Sako 85s. I try to have the rifle/scope zeroed at 200 yds with the scope adjustment approx. 25 clicks (1/4" at 100 yds) below centre at this zero as shown in the picture below. I set the BT rings at 300, 400 and 500yds. - David

 

[Fallman]

Fallman, that is very interesting. It looks as if mine were not isolated problems. What action / calibre is your Finnlight? Mine are the S (260) and SM (270 WSM).

I will be interested to hear how your gunsmith gets on with Beretta. However if he has no satisfactory response try my epoxy fix which is quick and effective once you have the custom grinding tool. Your gunsmith should be able to fabricate one without difficulty - might generate a lot of new work for him!

It is well worth the effort getting the Swarovski BT scope mounted properly as I really like the BT system, not to mention the clarity of the glass. I now have Z3 scopes mounted on both my Sako 85s. I try to have the rifle/scope zeroed at 200 yds with the scope adjustment approx. 25 clicks (1/4" at 100 yds) below centre at this zero as shown in the picture below. I set the BT rings at 300, 400 and 500yds. - David

View attachment 7154

David,
I have a 270wsm. I will let you know how the gunsmith makes out as I only found all of this out yesterday. I had always had trouble with the scope I was using and thought it was just me. My son gave me grief on a regular basis about how much time it took me to get comfortable behind the scope. It could well be that with the scope at the ragged edge of the elevation and windage adjustments, it was more difficult to get a clear sight. Everytime I got behind my sons rifel with his Swaro it was just so nice. So I decided to get rid of the scope I had and I was purchasing a Swaro Z6 3-18X50 with the 4W reticle and had the intention of getting the custom BT made that would bring me out to 900yds. When out in the desert looking for coyotes if I see one I would take the shot. For all my Deer and Elk I usually hunt Colorado and for Pig I hunt in Northern and Southern Cal. so the average shot would be 300 and under with some shots out to 500. All around I was really excited about the scope and now I am just totally bummed out. At least I didnt purchase the scope yet.

 

[David_S]

Fallman, don't give up on the scope, that windage reticle is excellent - simple and sharp without cluttering the sight picture unnecessarily. And you can always use the Optilock two-piece bases if necessary. These have the same rotating plastic inserts, which I like, as the one-piece ringmounts and can be shimmed readily with the traditional beer can shims. We have done this successfully on our M995 6.5x55.

It could well be that with the scope at the ragged edge of the elevation and windage adjustments, it was more difficult to get a clear sight

That's more than likely.

My son gave me grief on a regular basis

I find sons do this regularly. It's a pain when they are right!
David

 

[sako 22 250]

Hi Fallman ..I agree with David...I had the same issue with my 85 varmint and Zeiss scope using just the rings .. When sight in at 100m I had 2 clicks of up left ..not good , this was fixed when I went to optilock base and rings.. Didn't even need to use shims
Now have 27 clicks (27 cm @ 100m) of up avilable
Good luck
Mark

 

[Fallman]

Guys,
Thanks for the info and help. I am waiting to see what happens with Beretta. At this point all options are on the table, up to and including selling the rifle. The scope, which I really like has 90 clicks of adjustment above and 90 below for elevation. I need to get it zeroed and have at least 60 clicks left in order to use the Balistic Turret in the form of the customized BT. The rifle has approx 300 rounds thru it as I keep records of all my shooting. I will keep you all posted and appreciate the inputs. At some point I may give you my cell number so we could chat if thats ok with you guys.
Thanks

 

[David_S]

Didn't even need to use shims
Now have 27 clicks (27 cm @ 100m) of up avilable

Mark, if I was you I would still shim that scope to bring your zero range position to at or, if you use the turret clicks to compensate for longer ranges rather than hold over, below the mid point of the scope range. My Zeiss scopes (3.5-10x44) have a nominal 272 click adjustment range so at my zero range I would like to have at least 136 clicks left above and preferably something like 150 as I use the turret clicks for longer ranges. The 27 clicks that you have means you are operating near the outer limit of the scope adjustment. Shimming those optilock two piece bases is pretty easy. It involves either trial and error or careful measurement and calculation and not so much trial and error! - David