Accuracy .. vanished.

jaycee

Hi All...

I have a little BRNO .22LR which has always proven to be an accurate little gun,
If I do my bit ..it will produce occasional 5 shot groups @50 yds with all the bullet holes kissing .. I use it mainly for informal target practice .

Suddenly .. out of 5 shots ... I get 2 shots together then the other 3 will scatter up to 8 inches from the main pair .. it isn't always the first 2 that group.
I can't see a pattern to it ..
The gun hasn't been dropped or abused in any way , it's cared for like a baby.

I have tried 2 different scopes ..no difference.
Really thorough cleaning ..no difference.
I'm using Lapua subsonics ..which usually shoot very well from this gun.

Trying to zero the scope is a nightmare.
The whole thing defies mathematics .. there is no consistant result to making scope adjustments.

The barrel was free floated a couple of years ago ...

On examination the bore looks perfect ..
I don't think it's a wear issue as this was a very sudden change.


Any Ideas..?

ozt9vdujny3srf

Defies mathematics.....

nice.

civdef

That sort of sudden change pointss to a sighting problem. You've swapped scopes, how about mounts?

If the rifle has iron sights, try them out - should narrow the problem down a bit.

Citizen_Erased

It really does.

Just to test , ignore the zero for a moment and just put down five rounds with the crosshair on the centre of the target. It dosent matter where they are on the target just how well grouped the are.

Did your mounts come loose , it sounds as though they may be sliding about?

jaycee

Ok..

Yes I swapped scopes ..after this problem appeared.
No , I didn't change mounts , because both scopes have one inch tubes.
I did check the mounts for tightness and they seem ok as in..(Bloody tight.)

There are iron sights .. I might try that out.

Just BTW..
I did try ignoring the zero and just shooting for groups ..
Thats when I started to get worried ... as I said above most 5 shot groups will have 2 of the string pretty close together.. the other three can be anywhere ..up to 8 inches away from these at 50 yds... Scary .

And before anyone thinks it... I'm not olympic material ..but I don't shoot that bad ...

Citizen_Erased

This may be an insult to your inteligence but where you outside in blustery conditions?

jaycee

This may be an insult to your inteligence but where you outside in blustery conditions

No insult taken...

Very light breeze .. I'd reckon perhaps 5-10 mph..
I've shot in far worse without drama.

Citizen_Erased

Duno then , this is one for the more knowlegdable folk.

Umiq88

how about securing the rifle somehow so i cant move and taking 5 shots out of it

Croppy Boy

Had something like happen to me . Turned out one of the mounts had a screw in the middle for anti recoil. This had been tightened when first mounted. The scope was taken off and later remounted but the little screw left that mount slightly canted to one side making it impossible to zero.

jaycee

Thanks for the suggestions guys..
Last night I stripped down the rifle and retightened all the screws.
I also put some lock-nut on them to prevent them working loose again.

I also took a long hard look at the scope mounts and their point of
contact with the dovetail .. I then tightened these as much as possible.
I bore sighted the rifle and remounted the scope ..

It was too dark to do any more so all will be revealed when I get a chance to
shoot it again.

I shall report back on progress or the lack of it.

jaycee

Ok..

Former accuracy restored ..
What caused the problem... dunno

All I know is that I tightened everything up to the best of my ability..
used copious amonts of "Lock-Nut" and have been rewarded with the kind of groups I would expect from the rifle.

The effect may have been the result of several small factors ..
But the one I point my finger at (At the moment) is that the front swivel screw end was protruding through the stock enough to be touching the barrel sometimes.

It's my best bet..

Citizen_Erased

Well ,give yourself a pat on the back

jaycee

An "Interesting " footnote to this saga ..

While doing a bit of "Tidyin' up " this evening I had a look at my backstop.
(A series of rubber mats then MDF boards and finally a steel plate)

The thing I thought that was odd was that in the area where some of the "Flyers" had gone I retrieved some almost undamaged bullets embedded in the outer layers ..

These were in good enough condition that the rifleing grooves on the bullets were sharply defined and the shape was undeformed .
Ones retrived from the center of the target area were flattened.

I just started to wonder if there was the odd underpowered round in that batch.
It was Lapua subsonic club.

Citizen_Erased

I always wonder is it possible to get dud rounds? My old air rifle would occasionally and randomly just drop one shot about 6 inches off aswell.

Sparks

It's definitely possible. I've had Eley rounds keyhole on me at 25 yards, so cheaper Lapua stuff at 50 yards is definitely able to do that kind of thing.

civdef

Usually if rounds are "squibs" or similarly underpowered, you'll hear it before you see it.

It reminds me of shooting cheap Remington Thunderbolt ammo, that was so inconsistent the best description of the sounds on firing would be "snap, crackle & pop".

jaycee

you'll hear it before you see it.

With a moderator ..?

mifyah1

Regret to say I have come across 2 similar cases. A pattern, I fear. 3,000 rounds may be the life of some CZ (as opposed to pre 1990 Brno) barrels. A thorough cleanout and a different brand of ammo may produce an improvement.

Ammoman

He has sorted the problem probobly a loose scope mount or something , I have seen that happen before . The problem with .22 ammo is that it is mass produced with quite poor QC checking , unless you go for the high end stuff . I have always found the Lapua Club standard ammo in the tin quite good , but the odd flyer still happens.

Rovi

Ammoman wrote:

I have always found the Lapua Club standard ammo in the tin quite good

Yep, me too.
For ammo that comes 500 at a time in a 'big can o' bullets,' I've never had reason to blame the ammunition for the many funny looking groups I've produced.
Now, if you want inconsistent, get yourself some Eley, and prepare to tear your hair out

jaysee said somewhere in this thread that he suspected that the front swivel screw was touching the barrel, and I'd reckon that this was the cause of his troubles.

.

Ammoman

Rovi wrote:

jaysee said somewhere in this thread that he suspected that the front swivel screw was touching the barrel, and I'd reckon that this was the cause of his troubles.

.

Yes , that would do it , He must have put in a different type of sling stud at some stage , because the factory one could never reach the barrel . i remember a number of years ago that ely had a problem with Eley Club , i think a couple of guns blew up.... Not in a big way , but blew the bolt up in one case.. :eek:

you dont know what your ammo is like until you squeeze the trigger...