Brno 602 416 Rigby shoots low with scope

[fourfive8]

If you shim under the base then lapping is essential to return the rings to stress free mounting of the scope.

Yep, I use these along with lapping compound for all scope mounting. Seems there is always I little run out no matter how close things appear. Shimming enough to get well over 20 MOAs of correction is a lot! and will require some dedicated use of lapping bar.

 

[steve white]

I have the same scope and LOVE it for low light--probably the best on the planet for that...but if it needs attention, Zeiss WILL warranty it. Good luck getting it straightened out. I personally would not settle for less than a mounting that would allow me to keep the scope adjustments AS CENTERED AS POSSIBLE. I also esteem milling as better that shimming, and lapping as a last resort due to polished inner surfaces of the rings letting the scope slip under recoil. (perhaps leave them a bit rough, or add some resin powder to hold them in place--if anything will slip, a 416 will reveal it!)

 

[steve white]

It is a well known problem on a few of the ZKK602 rifles. I sold my .458 Lott for that reason. Tried everything then eventually realized the axis of the barrel wasn’t true to the axis of the action because the thread in the action was skew. In effect the barrel pointed downward out of the action, causing that 40 MOA difference.

Then CZ should warranty it, or catch hell in reviews--that is a LOT to be askew between action and barrel due to threading, etc.! Of course, you COULD choose this time to get the whole rifle trued up as in custom aftermarket accurizing, but if I went that far, I'd probably have a premium barrel installed as well, and then you're way past the price you originally paid. Not saying it's not worth it to have a true cloverleaf shooter. I know lots of people that consider such workup to be SOP...and of course, going that far will slick up the action as well.
PS, I have had two Sako rifles where one recoil lug was totally out of contact, plus bedding related problems, so no use picking on CZ.

 

[fourfive8]

Hm? Any progress on the mounting problem?? If it were me, which it isn’t of course, I would get a set of Leupold ring mounts for the CZ 550. About $80 with free shipping from Midway. When tightening down the front and rear ring mounts to tha action dovetails use a length of 1” bar clamped snugly in each mount. Then get or borrow another scope that is known to be sound- doesn’t have to be fancy, European or expensive. Mount it in the ring mounts and bore sight using a vise or cradle and a large black bull at 25-50 yards?- range doesn’t matter much. That will answer the most basic questions about what may be going on. Then proceed with the information gleaned or take it to a gunsmith if required who knows what they are doing.

As an aside, I know that vertically split rings have been the rage because they are different and cool looking…. but there is mechanically no way to properly balance the torque/ tension on those between the force applied between the base dovetails and the scope body itself. The system is a pivoting lever that uses the scope body as the pivot. Something to think about. Just saying

 

[fourfive8]

Here is a Leupold 1.5-5 mounted on my BRNO 602 375 HH. Pics of both sides of rear Leupold ring mounts. Hard to be simpler or more foolproof.

 

[PHOENIX PHIL]

Here is a Leupold 1.5-5 mounted on my BRNO 602 375 HH. Pics of both sides of rear Leupold ring mounts. Hard to be simpler or more foolproof.
View attachment 451707

View attachment 451709

What is your method to ensure the rear bottom half is lined up with the front? Other than just eyeballing it.

 

[fourfive8]

This exercise has been aimed at identifying or eliminating where the source problem is with the OP’s rifle/scope. This is a two piece mounting system by design of the rifle. Theoretically the flat top bridges and dovetails on the BRNO are on same plane and same axis. Just trying to determine here what is out of kilter with the OP’s set up shooting 20 MOA beyond the adjustment capability of the scope. Is it a rifle problem? Is it a scope problem? Is it a mount problem?

Using known, simple mounts like the Leupold mounts described above and a scope known to be sound… Take a 1” bar and slip fit clamp on front and rear ring mounts. Put front and rear ring mounts onto their respective dovetails with the rear mount’s tab centered in the bridge’s slot recess. When satisfied with positioning, slightly tighten ring mounts to bar. Then finish tightening dovetail clamps on bridge dovetails. Remove bar and replace with test scope. Snug down test scope. Turn scope’s elevation and windage to adjustment midpoint. Bore sight on black bull. If bore is no where close to scope and scope won’t adjust to bore center… could be rifle.. ughh.

Worst case scenarios could include bent barrel or barrel cattywompus to receiver. Scope or mount issues should be identified by using known mounts and known scope. In that case, a correctly identified problem- easily fixed and relatively inexpensive. For the possible worst cases, be prepared for down time and several hundred dollars to a gunsmith.

And if worried about the QR function which I question the necessity of anyway.,. just carry one or two of these “levers” with you- dime a dozen.

 

[Aleksj89]

Sorry for the late reply, been working day and night lately.
Tried with a different scope, one of my Swarovski z8s witch has more elevation and that "solved" the problem. So the Zeiss isn't the culprit, neither is the rings but im still going to change them out for something ells. The Warne rings just give me a good feeling.
The debris that is visible inside the rings on the pictures are leftover resin that shines good with the photo light on.
I can give it a try without screwing in the front screw this weekend and see if that helps, as my gunsmith cant straighten up the barrel/action without changing the barrel and I dont think ill do that before i have tried to sort it out with another scope or mounts/rings.
Thanks for all the advice and info on scope mounting, i will look into it.

 

[fourfive8]

Sounds good. Thanks for the update. Always best to try to figure out what is going on and correct if possible before taking it to a gunmith. Doubtful the front barrel screw, whose nut slides in the track in the short under barrel rib, can put enough tension one way or the other on the barrel to change the POI as much as described. If anything that screw, which is similar to the old Win 70 front screw, will primarily affect barrel harmonics. The whole barreled action of the BRNO should sit in more or less full contact with the stock before tightening down any of the action screws.... unless of course the stock is warped or something else in not right. It is not a floated barrel fit from the factory. Like some Mauser actions, they have a pillar bedding of sorts in that there should be thin steel tubes lining the holes in the stock. I assume a design to prevent wood compression/stress when tightened.

 

[Aleksj89]

I tried to write that the warne rings dosent give me a good feeling in my last post, but i guess my proof reading cant catch all my typos.
The fit of the barrel and action is really tight, it's an aftermarket stock with a good job on the bedding, so i dont really think it will have anything to say if i tighten the front screw or not but i will give it a try. A guy i know have a 20 moa picatinny rail for the 602/550 with 20moa that i will try out with some burris xtr signature rings i have lying around to see how much the barrel is of, i think i can get 40moa just with the nylon shims in those rings.
That should get me the elevation i need until i get the barrel switched out and the threads of the action straitened. But i feel i'm committing sacrilege by putting a picatinny rail on a 416 rigby

 

[Dewald]

Do yourself a favor and get the barreled action to a competent gunsmith to put in a lathe and measure concentricity. Its the easiest way to see if the barrel is bent or not true to the action. (Which explains good accuracy with iron sights, as both are mounted on the barrel)

 

[fourfive8]

For a real eye-opener, especially when using two piece mounts Mount these with the points nearly touching.

Instant feedback on alignment of front and rear ring mounts. Really handy when using dual dovetail mounts or for assessing off-axis mounting torque on scope tube.

 

[ducmarc]

I used a pair of Leopold bases on one of my m70s with Burris rings they came with internal shims that can correct this problem.

 

[Lone Star Bluegrass]

Thanks for all the great answers, english isn't my native language and im without power due to storm but ill try my best to answer you all.
I did initially think it was the rings that were the problem, so started to look at those. They are even in height and looks good, it's the warne rings that is for the CZ/Brno rifles with the recoil lug.
The reason I went with that scope is because i'm mostly gonna use it for deer and wildboar hunts that takes place at dawn or evening/night time.I got alot of other scopes i could try out but i dont think a brand new zeiss scope would be the reason why i have maxed out the scopes elevation at 100m, but i will try to switch it out if i cant find out were the problem is.

It is the original barrel, almost unused.
I have checked all three screws that connect it to the stock, its an aftermarket stock that is bedded and fitted vel by a gunsmith. Grouping isn't the problem, it shoots well with cast bullets, 350 gr speer, 340 sonic brass bullets, 400 grain woodleigh etc It's just weird that a scope with so much elevation has to be maxed out at a 100m, and when googling around i came over the thread on this site that brought up the problem with the barrel/action alignment.

When i get power back will i take a closer look at the rings, but they look good and even in hight. I did boresight it before shooting with the scope in "the middle" on both elevation and windage and could see that i had to screw alot up to get onto the target. I'll take another scope with me on tuesday when the range opens to check if it can be the scope.

I dont think that the scope is too high above the barrel to be the issue, but im no expert. I have to use the high mounts to stay clear of the rear sights on the barrel.

You said it shoots well with cast bullets, 350s, and 400s. What velocities are your loads? If you’re running everything at cast bullet reduced velocities you’ll have an elevation change.