.22RF zero problem - advice please

[J@son]

So... I have a CZ Brno 452 Varmint which I have owned for 15 years and bought new. It's never given me any bother until recently when I felt it was no longer holding zero. I blamed the sight which I replaced with a new Wulf 4K and thought I had solved the problem. Until today.

Went out to check the zero and put seven shots at 35 yards on top of each other. Then went back to 55 yards and added three more to a group that was 2 cm across. So far so good.

Then I got a flyer - POI was inline with the centre of the group but 5 cm above it. And that is when things went south. I must have put at least 150 rounds through the gun this afternoon but my shots kept drifting up and down. My horizontal aim point to POI remained pretty much spot on - 1 cm drift either way. But my vertical aim point to POI was all over the place - sometimes high usually by 5 cm, sometimes low again usually by 5cm, sometimes spot on.

I tried allowing the barrel to cool down. I tried running a bore snake through it. I could not achieve a consistency.

This is exactly the issue that prompted me to change the sight in the first place. I feel like I am back to square one.

I don't think it is the sight. I don't think it is me. I don't think it is the ammo. I think it is the gun.

What should I do? I have never deep cleaned it but I always run a bore snake through it a couple of times before putting it away. Should I get the barrel inspected by a gunsmith? Advice please. Thanks

 

[Pellet Pinger]

Is your mod on tight?

 

[bbrc]

I would guess at something loose, bedding screws, moderator or moderator internals

 

[Iamtheferryman]

I have had similar issues and found it was the ammo....... Winchester subs. I am going to be trying different brands soon

 

[snake_2586]

Yeah I would make sure the bedding screws are tight and then shoot a group without the moderator fitted and see what its like.

 

[Bowland blades]

Moderator or duff ammo , outside chance of dirt or debris in bolt or chamber . If its Winchester look right there ! I had a box and some where so out on the rim they woulnt fire or eject . took them back to the dealer and they sent the whole shipment . Later i read that the manufacturing was in Australia now and QC took a massive hit in quality .
I have shot poor ammo through that gun and brilliant ammo but to have some fail to fire or eject is beyond bad

 

[Smellydog]

At least try some different ammo first

 

[bowji john]

Vertical stringing is commonly associated with velocity spreads

Can you measure the velocity?

Another simpler idea is the wind - especially if it is from behind or ahead

 

[VSS]

Twice I've had similar with my 22lr.
First time the mod needed stripping down and cleaning. (And I put all the baffles back in wrong afterwards, which made things worse ).
Second time it was ammo. Remington. Load of rubbish.

 

[HonestJohn]

Check all screws, try with different ammo if that doesn’t solve it. In a .22LR not much else can go wrong unless your scope is knackered

 

[Smellydog]

Take the mod off, piece of junk anyway

 

[Friendly Boar]

I have the same 452 in CZ , deadly accurate, one outing let me down, had to clean everything put it back together and tight and back to being perfect.

 

[HonestJohn]

Take the mod off, piece of junk anyway

Yes! For all rifles in general!

 

[Smellydog]

Yes! For all rifles in general!

Lol, I've got them on my rimfires but I don't know why really. Might take them off.... again.

 

[John Doe]

My money would be on the scope. Can you swap it for a normal optical scope to check?

 

[J@son]

Thanks for all the feedback and suggestions. Ammo was my first thought (Winchester’s are hopeless in my CZ) but I have already switched a couple of times without being able to produce a consistent POI. I am currently using Norma. I will experiment with/without the mod and check the bedding screws at the weekend.

 

[Sonicdmb73]

I have with more than one 22rf found that ammo that had been accurate for years in some cases. Stopped being accurate, ie groups opened up. All mechanical, cleaning etc issues checked/sorted or ruled out.
I would try check the velocity spread on the ammo. However you might consider that a change in charge weight to the ammo can make your rifle no longer "like" that type/batch.
Take a look at the process competition shooters go through with Eley Tenex testing many batches to find the best one.

 

[webley701]

J@son,
Do you think a proper cleaning of the bore would be a good first step?

 

[nic531]

check the mounts on the scope.
just work your way down a list
gun clean and everything tight, no loose bits barrel not knackered
ammo - try 2 or 3 brands
mount
scope
mod - on/off
indoors/outdoors - wind
fix in vice/bench rest and see if still a deviation to take shooter out of equation

looking for group not groups position, that can always be altered later

 

[Phil fox man]

I fixed a keeper friends Brno doing the same thing,he had put a new sling mount on and the screw was touching the barrel.
check for the barrel float or remove the front sling screw and shoot off bags.
sounds to me like the barrel is being affected by something.