BRNO Zernoing problem

BRNO. Grant

Hey all, Can anyone help me with a zeroing problem.
I recently bought a .22LR Brno bolt action. its an older model with 15mm dovetail, so mounts were hard to come by.
when zeroing sights at 25 yards, at maximum elevation, the grouping is still about 3 -4 inches too low. i have bought a new scope and this is still the case.
the open sights give a perfect group at 50 - 60 yards. so its not the gun, and since i have tried two scopes its not them.
that leaves the mounts. do i have the correct ones?
Does anyone have an older model BRNO about 10- 12 years old with the same problem.
Also i have tried shimming the mounts up , but this doesnt work either.
any help is appreciated.

Vegeta

So the rifle is shooting low at 25 yards and obviously when you try to zero it out further the rounds will just hit the ground or whatever.

This may sound stupid (or you may have already tried this) but try twisting the elevation the other way and see if it gets worse or better.

Happened to me when initially zeroing a .270 sako. The rounds were about 3 inches low and when i adjusted the elevation they went even lower so maybe try going the other way.

BRNO. Grant

Yes, I have tried it to both the maximum and minimum on elevation. just drops lower. what i am thinking is that it might be a imperial mount i.e in inches rather than mm.
i have put a collometer on it and it is low on this also, so im almost sure its the mounts
would you have the number or webpage of a gunsmith.?

jaycee

I presume you have checked that they aren't canted mounts ,
with one higher than the other . If so try swapping them .

Vegeta

BRNO. Grant wrote:

Yes, I have tried it to both the maximum and minimum on elevation. just drops lower. what i am thinking is that it might be a imperial mount i.e in inches rather than mm.
i have put a collometer on it and it is low on this also, so im almost sure its the mounts
would you have the number or webpage of a gunsmith.?

Sorry i don't have the number for a gunsmith but if you give the model of the rifle maybe we could do a search for suitable mounts.

I find it hard to picture why the mounts would cause a problem. Are the mounts and scope very high on the rifle or of equal height as Jaycee points out??

BRNO. Grant

Yea, ive swapped them around, i thought about that, and took the bolt action out, lined up the barrell on a target. then set the mounts & scope up, 2 see if they were anyway close to the same target, they are high, when i loosen off the back mount and lift it slightly the scope meets the target.
i have enquired about "canted" mounts but cannot seem to find any for 15mm dovetails.

jaycee

How about "Shimming" the scope ..?

BRNO. Grant

No mounts and scope not that high at all. Just the normal type. 4* 40 scope on a 1" mount with 15mm dovetail. its unusual,

BRNO. Grant

How would i do this without folding the main body of the scope,. or is it the mounts i shim.

Vegeta

BRNO. Grant wrote:

How would i do this without folding the main body of the scope,. or is it the mounts i shim.

ok word of warning here, be careful not to damage the scope itself, if you raise the back scope mount and then tighten the mounts on the scope you could damage the tube. If the mounts have internal rings then you will probably be ok.

jaycee

Here's a guide ...

http://www.charm.net/~kmarsh/sighting.html

17HMR

I use one of these on my CZ/BRNO .22LR

http://www.airguns.net/reviews/sportsmatch_adj_mnt.html

You can bore sight using the mount adjustments (can adjust for elevation and windage) and then fine tune with the scope adjustments.

BRNO. Grant

Will that mount fit a 15mm dovetail?
will try the shimming once all else fails, hate 2 ruin a good scope.. things can get expensive ...

17HMR

Ah....
Had to look that one up. Nope. Sorry. 15mm is too big. Spec is 9.5-11.5mm I'm afraid.

AOP55 One Piece Double screw mount adjustable for windage and elevation. Suitable for all spring guns / semi auto.22 rimfire rifles. Suitable for some pre-charged pneumatic air rifles such as BSA SuperTen and Air Arms Pro Target. Air Rifle / .22 Rimfire 1" High range for 9.5 mm - 11.5 mm dovetails up to 56 mm Lens Dia. N.B. Will clear 60mm objective lens dia. on most rifles. Includes removable arrestor pin

BRNO. Grant

Yea it is very difficult to find any parts for older BRNO rifles, all newer ones are standard 11.5 to 13mm i think.
I just have to persivere. A local gunsmith reckons the mounts are too low, and that the bell on a 4*40 scope would probably not run parralell with the barrell. Might try the shim this evening and see how its goes.
Thanks for all ye're input guys, much appreciated.

17HMR

You could aways try

http://www.czshooters.com/

For all things CZ.....

civdef

www.czforum.com or the CZ section www.rimfirecentral.com would be other good resources.

thelurcher

What you need are the Burris Zee rings with the full set of inserts.
They are similar to the sako optilock mounts in that they use a plastic insert but you can use inserts of different thicknesses front and back to 'angle' the scope the way you need - they take a bit of time to set up though.

The problem then will be an adapter to fit - might be worth sending a mail to Eric Brooks on this site:
http://www.cz452.com/
He's very good to deal with.

thelurcher

Eric has a Burris section on his site now as well - just saw it there!