Vertical Stringing

[Nigel Nobody]

Hey guys

Has anyone ever had their 22lr suddenly lose its accuracy?
My std CZ 452 has been a tack driver from new almost 10 years ago.
As it was always capable of at least a few single ragged hole groups on any range session whether the barrel was clean or dirty, I just ran a few wet and dry Hoppes#9 followed by an oil patch after every shoot.

It just stopped shooting well and the pattern was a real low 1st shot up to 2" 2nd shot about 1" low, then worked up to the 10 ring and starts grouping OK.

It got a new scope and eliminated ammo and all the usual things.
Then scrubbed and scrubbed the chamber as a carbon ring was suspected, then bought a Teslon bore scope.
It seemed to be shooting well on rimfire silhouettes getting strings of 4 hits in a row standing pole-supported.

Last week in good conditions I shot some groups and they are near enough a straight line with the same vertical dispersion.
Could bet on the super low 1st shot , then climbs and starts grouping.
Shooting it's fav SK std ammo and by the 4th group it starts shooting well including 5 touching.
Put it down and shoot another rifle, pick it up and load up some mags with CCI std and it shoots a few identical 3-4" straight line groups and then starts shooting OK.

Previously if ammo testing and unsure, I could just load a mag of SK and it would often shoot a single hole, no need to shoot the same ammo.
It can only be the rifle or stock causing it and the dollar note feels the same as always, clearance and only tight up near the action.
I have been working up with action screw torque and was up high at over 25 inch/lbs so have backed down to about 15 and 10 on that middle screw. If that's not it, I may have to sand the wood a touch in the barrel channel.

After that, I am out of options and my local gunsmith can look with his bore scope and check out my targets.

So sad as it was my first rifle and always shot like a laser, often I could put 10 shots out on the 200yd target without a big scope, just walk the shots onto the target and aim a rock above. Often got a fist-to-hand-sized cluster with 1 or 2 flyers.

Do you blokes know what these straight line groups working up can be caused by?

 

[RTH1800]

You seem to have addressed the likely suspects.
Think scope, bedding, carbon ring and ammo. If you rule these out consider inconsistent ignition from dirty, damaged firing pin or weakened spring.

Last item on list could be crown damage , bore wear or damage from improper cleaning. (Rod wear)

Rinse, isolate variables and repeat.

 

[Nigel Nobody]

I can't imagine that I damaged the crown and wasn't even shooting it much or in the field.

The one odd thing was CCI Velocitors became available and I tried a pack.
They shot so well that I returned for a brick.
The only HV ammo the CZ ever liked enough to shoot a 1/2" group before was CCI mini mag.

The odd thing was a slightly tight bolt close using the first few packs of Velocitors yet I didn't notice it after that.
The rifle cycling and bolt had never faulted on any ammo previously apart from some ammo having the odd one not go off, never CCI though.
I wonder if that did something with the bolt to change headspace or something?

 

[RTH1800]

I’d say that and mild steel is the issue.

 

[beetroot]

I've been struggling with excessive vertical stringing with my T1x, causing me a lot of grief.

Do you use a suppressor?
It's usually lead fouling in the suppressor or carbon ring that causes it.

Does your bore scope show that the chamber is spotless?

 

[Nigel Nobody]

I’d say that and mild steel is the issue.

I don't understand what you mean, mild steel bolt and the tight chambering CCI Velocitor rounds?
Do you think this could have caused a change, like in headspace or something?

It's the only thing that has changed in many years.
Also rather than Hoppes on the couple of wet patches to clean, I have just used Inox.
It's like a lanolin based light cleaning oil that I thought would clean the 22 fine.
It may not maintain the chamber as well and let a carbon ring develop though.
I use it to protect all my rifles although I have all the exy products like G96, Balistol. and Rem oil.
I often get a blue copper color when I run a dry patch through a centerfire barrel before shooting so it has a cleaning effect like Rem oil as I noticed the same.

 

[Nigel Nobody]

I've been struggling with excessive vertical stringing with my T1x, causing me a lot of grief.

Do you use a suppressor?
It's usually lead fouling in the suppressor or carbon ring that causes it.

Does your bore scope show that the chamber is spotless?

I wish, but in WokeWorld (Australia) supressors are highly illegal and normal rec shooters would lose their licenses, only available to the useless govt chopper bomber shooters and some pro shooters that jump through an extra 100 hoops and pay the 100 fee's, most will still be rejected as silencers could turn us into James Bond types sneaking around shooting people at night, yes our govts ARE that stupid.

It's a good question as my bore scope doesn't show it as perfectly shiny steel like I seen on a uTube vid.
He just soaked it and wiped it out, maybe a better quality match barrel.
Mine looks like it still could have carbon and rougher machining.
I must have soaked and cleaned it about 5 times now, even used some JB bore paste.
I now have a big $80 bottle of Boretech Eliminater and used it as well.
I can now take photos using another memory card so will try and add pics latter.

Tomorrow, I will drive down the coast (about a 4hr round trip) as a gunshop has got their shipment of White river primers and a box will make my supplies look much more secure into the future lol.

 

[beetroot]

I wish, but in WokeWorld (Australia) supressors are highly illegal and normal rec shooters would lose their licenses, only available to the useless govt chopper bomber shooters and some pro shooters that jump through an extra 100 hoops and pay the 100 fee's, most will still be rejected as silencers could turn us into James Bond types sneaking around shooting people at night, yes our govts ARE that stupid.

It's a good question as my bore scope doesn't show it as perfectly shiny steel like I seen on a uTube vid.
He just soaked it and wiped it out, maybe a better quality match barrel.
Mine looks like it still could have carbon and rougher machining.
I must have soaked and cleaned it about 5 times now, even used some JB bore paste.
I now have a big $80 bottle of Boretech Eliminater and used it as well.
I can now take photos using another memory card so will try and add pics latter.

Tomorrow, I will drive down the coast (about a 4hr round trip) as a gunshop has got their shipment of White river primers and a box will make my supplies look much more secure into the future lol.

Starting at 15:00, is the method I use to clean the chamber.
If the rifle when from shooting well, to vertical stringing then the chamber would be my guess.

 

[RTH1800]

I don't understand what you mean, mild steel bolt and the tight chambering CCI Velocitor rounds?
Do you think this could have caused a change, like in headspace or something?

Yes, if soft steel, forcing in rounds and firing higher pressure rounds could have expanded headspace.

 

[cbailey]

Might try disassembly of bolt and clean all parts good. erratic ignition can cause similar problems. no oil on spring when reassemble. just some lube on cam points. maybe a new spring? just a thought. good luck

 

[RTH1800]

I agree with above except it does not explain the difference feel of the bolt closing. I'm thinking the action is "sprung" and headspace opened up.

 

[Lastsaint21]

Same as what Cbailey said, for me it was my bolt.. If the firing pin doesn't hit with the same force you wont get the same results assuming the ammo is good. I seen it personally with my own Vudoo, and on a RimX..

 

[cbailey]

do velocitors have the longer case than regular lr case. maybe pushing the longer case into tight chamber?. Does your borescope show any carbon buildup just before the chamber taper? I use boretech c4 and let it soak in that area and the first inch or so. Nylon brush later usually takes it out. any buildup in that area of the chamber will give problems (chambering and erratic accuracy). I use a nylon brush so I can stroke back and forth and spin it by hand. many automotive cleaners that remove carbon can be used in that area of the barrel if you dont have c4. good luck, chased many tails myself.

 

[Nigel Nobody]

I wish I lived on farm land and could shoot the 22 at home as the only option is do one thing at a time and test shoot. I only visit a range every 3 weeks or so at the most.

I will first eliminate the action torque and slight possibility of stock timber swelling as we had 3 very wet years but it seems to feel the same as it always did with the $note feeler gauge.

The headspace possibility is a worry and those tight bolt closings with the HV Velocitors is the only issue I have felt.
Will try a shim test with std ammo and see if I can pick up anything my self.
My smith is a nice bloke and will do a 10min check for free, I think, still best if I can point him in the right direction.

At least I am picking up tips and finding more when testing.
I am not too bad a shot and clearly seen the first 2 shots dropping low, 2 diff ammo types as well so it could still be a basic stock bedding thing. I will eliminate that first.

The headspace thing is a worry and the rifle is suddenly less ammo fussy, I noticed and could have something to do with it.
Just annoying as my CZ was always the only 22 I ever needed as it drove tacks at 50 and they are not supposed to wear out so I figured it is a lifer.
I do love the way CZ have addressed all the small issues in the 457 and that carbon model is a cracker, a match chamber as well.

 

[Nigel Nobody]

I did some checking when I first fired the new CCI Velocitors and felt the tighter bolt closing and couldn't pick any differences. They also seemed consistent enough with rim thickness as I made a gauge jig to do that on the calipers.
As the tight closings seemed to fade and feel OK, I prob forgot about that slight issue.
In reality, and the fact that the rifle has shot so well for so long, it may well be what caused it.

Another thing I noticed since the issue is the rifle is far less ammo fussy and some "best groups" on the days were often CCI std and even the Velocitors, other days it was the SK std+ that produced the 5 touching group.
Possible that looser headspace using the old best ammo makes them shoot worse and the Velocitors having less headspace make them shoot better.
Also seems better to keep shooting the same ammo where it didn't matter before.

I think I mentioned that the rifle always preferred std velocity subs and never shot decent groups with HV ammo apart from CCI Mini-mags.

Can't do much checking or get the bore scope out again until I finish a BIG batch of .223 reloading and clear the bench.

 

[Nigel Nobody]

Well I went to the closer indoor range again and the long saga seems to be resolved.
The first 2 shots were on target and I shot a few .4" groups at 50m.
No wild vertical stringing at all.

I think cleaning the bolt fixed it and I tried backing off and tightening the action screws just to see.
It shot fine at all torque settings so it's not sensitive to that.

I didn't shoot any real good single-ragged holes but got a couple of .4" touching groups so that will do me.
It felt so good and has been months.

The other pea-shooter, a .22 PCP air rifle also shot like a laser when I thought it had lost a bit.
Shot 2 groups under .4" at 50m so that is still shooting fine as well.

I just have to verify that it shoots well again outdoors and all's well that ends well.

Thanks for all the extra tips as it had me beat for a bit.