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CZ 452 2ZKM American Inaccuracy .17HMR


R6demon
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Hi All,

Sorry for the long post however, I am experiencing an odd issue with my CZ 452 which I bought SH around 3 years ago.  Having been away from shooting for roughly a year due to working overseas, my fellow PW member and I popped out for some social distanced Rabbit shooting on Monday.  After a quick check of the Zero at 100m everything seemed to fine however out in the field things started to deteriorate.

I was head shooting rabbits at around 50-80m no problem, then the next 3 shots completely missed the target, back to headshots, next 2 shots completely miss the target this continued sporadically throughout the night.

Having discussed it at length it was noted that I had never cleaned the bore of the rifle as that was the advice from the previous owner and a  number of other people WRT .17HMR. The rifle was purchased from an ex PW member and had apparently only seen a couple of boxes of ammo from new and was in VGC aesthetically ( I am new to firearms!)

I then spent the best part of 8 hours trying to clean the barrel, starting with KG2 bore polish, patching, soaking, brass brush on a rotating rod (only one way from breech to barrel) and patching dry, this process was completed over 20 times and the patches would still come out looking like the below pics.

10-DD2242-84-CA-4-A4-A-B7-B0-9279-A93-E8

54-D5-A420-242-C-4-A11-92-C7-6-CAB91-A18

C82-E8027-DFEA-472-F-B45-F-ECDA5-D4-BD1-

IMG-1182.jpg

E0-A247-B6-8-F3-C-4203-93-B6-AA2-FF9-FE4

I then found and old unopened  bottle of Tetra Gun Copper solvent and repeated the process above.  When this didn't have the desired effect i poured some of the solution down the barrel, left to soak for 30 mins and repeated the patching process.

This was repeated another 6 times in total in my quest for a clean patch!

I have now used over 250 patches and scrubbed the barrel over 200 strokes and the patches are still fouled! At this point I stopped, cleaned the barrel a couple of times with KG2 and put a couple of lightly oiled patches through the barrel.

Last night we went out into the field to check the rifle again.  To start with we ran a couple of patches of Bore Eliminator through and scrubbed as above.  The patches were slightly improved but still showing some deposits.

The first couple of rounds (Hornady V-Max) were used as fouling shots and then the targets were set at 50m.  All shooting was prone using a Harris BiPod and shooting bags.

Initially the groupings seemed good, under a thumbnail size for around 15 shots, we had the occasional odd shot but that was put down to me laying on the ground.

 

We moved to 100m and again, a couple of odd shots but the majority were within an inch for the first 10 shots. the rifle was zeroed and then it all started going wrong, 3 shots on top of another, 2 shots inches apart and so it continued.

We changed Ammo to Winchester, it got worse. We changed to Remington and suddenly 4 bulls eyes.  Then the next magazine goes back to un grouped shots.  We tried a new pack on Hornady - all over the place. Back to the original V-Max and three shots in a tight group, 2 slightly off.

Changed to Winchester, all shots on top of each other, next magazine all over the place within a 3in group.

And so this continued!

 

IMG-1185.png

 

Things tested in short as im waffling!

1. All scope fittings checked MTC Mamba 4-16

2. Moderator swapped for new

3. Moderator removed Mod is in good condition with the exception of a bit of clipping / blast damage to the very middle holes?

4. Different Ammo 

5. no visible damage to barrel, crown looks in VGC No signs of rust or deposits

The only feedback on the internals from my shooting buddy is that the rifling looks rounded where as on a CZ he would expect it to be squared off?

 

We are both baffled 😞

Any suggestions welcomed!!!!!!

 

 

 

 

 

 

 

 

Edited by R6demon
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41 minutes ago, London Best said:

Number 3 on your list rings alarm bells.......clipping moderator.

And you have not mentioned checking stock screws??

I will get a picture, but even with a new Mod and with the Mod removed, the issue was still present?

 

I will also check the stock screws this morning, although it all feels tight?

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Wouldnt explain the pics of the patches as they look as if the barrel is pitted in some way compared to the patches when i clean my hmr which come out uniformally dirty , but have you checked the barrel to see if it is free floating 

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5 minutes ago, telf said:

Wouldnt explain the pics of the patches as they look as if the barrel is pitted in some way compared to the patches when i clean my hmr which come out uniformally dirty , but have you checked the barrel to see if it is free floating 

Any tips on how to check this?

Looking down the barrel I cant see any obvious pitting, I will try and get a picture

Edited by R6demon
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22 minutes ago, R6demon said:

Any tips on how to check this?

Looking down the barrel I cant see any obvious pitting, I will try and get a picture

Get a bank note and see if you can slide it between the barrel and stock, are you shooting from a bipod?

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I had exactly the same with a new cz 455. Did all that you have. First 3 shots bang on, 2 random. I gave up in the end and got rid of it.

some while later, I was sifting through some targets and puzzling over them. I and thought that the only variable in the package was the magazine. Maybe there was a difference in the presentation into the chamber between the shells. Obviously the first rounds are under more spring tension than the last. So I thought maybe the last rounds were getting the heads damaged in some way. As I’d got rid of it, I couldn’t verify if this was the case. 
So, did you use different magazines? Had you bought a replacement magazine? I would certainly try loading a full mag, then ejecting them un fired onto a carpet or such, and look to see if there is any damage. Also try a session chambering one at a time without the mag, and also load 5, shoot 3, then reload and fire three so you are only using the first under more spring tension. 
 I would be very interested to see your results from going down this route, wish I had!
 

atb

t33

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30 minutes ago, kennett said:

Get a bank note and see if you can slide it between the barrel and stock, are you shooting from a bipod?

that seems to work OK.  Plus I have removed the stock (which was attached firmly) and there isn't any debris or marking on the barrel:

IMG-1186.jpg

 

This is the 'Damage on the MOD at the first two chambers, is this just muzzle blast damage?

IMG-1187.jpg

IMG-1188.jpg

IMG-1189.jpg

IMG-1190.jpg

 

The action removed - clean no markings

 

IMG-1191.jpg

 

The action, original trigger

IMG-1192.jpg

 

The stock

IMG-1193.jpg


 

6 minutes ago, turbo33 said:

I had exactly the same with a new cz 455. Did all that you have. First 3 shots bang on, 2 random. I gave up in the end and got rid of it.

some while later, I was sifting through some targets and puzzling over them. I and thought that the only variable in the package was the magazine. Maybe there was a difference in the presentation into the chamber between the shells. Obviously the first rounds are under more spring tension than the last. So I thought maybe the last rounds were getting the heads damaged in some way. As I’d got rid of it, I couldn’t verify if this was the case. 
So, did you use different magazines? Had you bought a replacement magazine? I would certainly try loading a full mag, then ejecting them un fired onto a carpet or such, and look to see if there is any damage. Also try a session chambering one at a time without the mag, and also load 5, shoot 3, then reload and fire three so you are only using the first under more spring tension. 
 I would be very interested to see your results from going down this route, wish I had!
 

atb

t33

Interesting thought, this was using two magazines, i will try the chambering now!

 

Edited by R6demon
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Synthetic stocks can be a weak point, if you shoot off a bipod they can flex and affect the harmonics of the barrel. I'd be surprised if it's a barrel cleaning issue, my hmr gets cleaned very rarely and always shoots worse after a clean, even my 223 doesn't get cleaned that often!

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My thought is a loose moderator or interior of it and the bullets are just touching on the way out as things warm up but you say it does the same with the moderator off.  Owned three czs in 17hmr and all have been tack drivers.  I rarely shoot more than one round at a time to check zero, maybe two for any adjustment ..rare.. I have never considered the 17HMR barrel getting hot enough to change the fall of shot as with a full bore but if you are shooting continuously could this also be a problem.  I had a VERY light barreld 7x57 and it would put the first two almost in the same hole and then climb an inch at a time to the left in a curve.  Never ever needed more than two shots in a hurry so it was not a problem.  Will be interested to see what you find.

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4 minutes ago, Walker570 said:

My thought is a loose moderator or interior of it and the bullets are just touching on the way out as things warm up but you say it does the same with the moderator off.  Owned three czs in 17hmr and all have been tack drivers.  I rarely shoot more than one round at a time to check zero, maybe two for any adjustment ..rare.. I have never considered the 17HMR barrel getting hot enough to change the fall of shot as with a full bore but if you are shooting continuously could this also be a problem.  I had a VERY light barreld 7x57 and it would put the first two almost in the same hole and then climb an inch at a time to the left in a curve.  Never ever needed more than two shots in a hurry so it was not a problem.  Will be interested to see what you find.

^^^^ This and the mod looks to be damaged but you have tried it without the mod so this is eliminated. There is nothing touching the barrel, the muzzle looks good and the chamber is not damaged (?) so I would look at the sights next. The scope and it's mounts. An occasional flier with HMR would not be unusual but certainly not like the patterns you are producing. 

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46 minutes ago, turbo33 said:

I had exactly the same with a new cz 455. Did all that you have. First 3 shots bang on, 2 random. I gave up in the end and got rid of it.

some while later, I was sifting through some targets and puzzling over them. I and thought that the only variable in the package was the magazine. Maybe there was a difference in the presentation into the chamber between the shells. Obviously the first rounds are under more spring tension than the last. So I thought maybe the last rounds were getting the heads damaged in some way. As I’d got rid of it, I couldn’t verify if this was the case. 
So, did you use different magazines? Had you bought a replacement magazine? I would certainly try loading a full mag, then ejecting them un fired onto a carpet or such, and look to see if there is any damage. Also try a session chambering one at a time without the mag, and also load 5, shoot 3, then reload and fire three so you are only using the first under more spring tension. 
 I would be very interested to see your results from going down this route, wish I had!
 

atb

t33

Interesting results, every couple of rounds I'm getting a small dent in the same place!  Thats the same with both magazines! This seems to be the later rounds in the magazine!

 

IMG-1194.jpg

IMG-1195.jpg

Edited by R6demon
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41 minutes ago, R6demon said:

This is the 'Damage on the MOD at the first two chambers, is this just muzzle blast damage?

No definite clipping.

You say the first few rounds are ok ?
Try this , fire a round, or 3 , barrel warms up, wait till barrels cools right down, 10 mins...

Try a few more , has it moved POI.

My money is barrel stock contact when surfaces warm up, bed the action with something to free float it again.

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I have the same rifle and moderator.

Just had a quick look at the moderator on mine and the erosion in the SAK mod is similar to yours but mine has had 5000 rounds through it.

I don't clean the barrel much and the zero is fine.

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1 hour ago, scarecrow243 said:

hi try zeroing without the bipod 

I started using the Bi-Pod as I noted the accuracy was all over the place.  its the first time i've used the Bi-Pod 😞  I was using quad stalking sticks up to that point.

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2 hours ago, R6demon said:

Interesting results, every couple of rounds I'm getting a small dent in the same place!  Thats the same with both magazines! This seems to be the later rounds in the magazine!

 

IMG-1194.jpg

IMG-1195.jpg

Hmmm, interesting. So looking at those the dent becomes greater with each shell if they are in order of ejecting. I’m not sure how much less volume would be caused by the dent, which could affect pressure. But I can’t imagine it’s without some effect?  I note also possible clipping on mod, but you’d tried without the mod and still had the same problem. 
I was also told could be scope, mounts, barrel not floating, clipping mod etc. My money is still on the chamber end and before the shot is fired. 
See if the case gets dented when just chambering One at a time without the mag. If it doesn’t go for a session and see what the accuracy is like. If all ok, then the mag feed/ denting is the issue.

I don’t think the scope is an issue as your op stated, 3 good shots, 2 bad, then same again. I can’t See how a scope can jump back and forth to zero, all over the place, yes, but not re zero.

 

Edited by turbo33
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....quote... I can't see how a scope can jump back and forth etc etc....  Yes, it can , been there done that.

I cannot remember ever putting a rod through my 17hmrs and they have all been tack drivers, scary accurate and shoot far better than I can.  I had the American first off and sold that to a farmer firend who still has it and calls me continually to rave about how accurate it is.  I would doubt very much it is the barrel....NOW  no deisrespect honest but we all snatch one or two occasionally.  If you can sand bag the rifle and  obtain a 'hydraulic' trigger release,  then test the rifle with no human interaction. I have done this with a 458 Win mag and surprised how litle the rifle moved when fired. You expect it to leap about the place, it doesn't.   I spent 14 yrs shooting rifles professionally and believe me we can all snatch one or two occasionally.

You mentioned shooting off shooting sticks ...ertainly not a way to find out just how accurate your rifle is, too much human intervention. You must shoot off a sand bagged firm base with total control off the rifle, even with a 17HMR.    It's funny but I have a NV with a screen and find that I can hold the cross hairs much steadier looking at that screen than holding the stock and looking through the scope. Less human intervention.  I only have my hand around the grip and finger on the trigger, the rest of the rifle has no human intervention.

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I agree with above .

Ive had duff scopes  

Go off zero then back on again.

Back and forward .as you shoot .

Scopes   have  small springs (coil or leaf ) that rely on friction to stay in place..

Recoil can easily effect the zero .as it changes the friction .if your scope is far from optical or mechanical zero .

(Optical is when the x hairs are dead centre of the front lens element - as far as the polishing ground is concerned )

Mechanical is when its centre of the scope tube (and should be  when your at the centre point in terms of clicks of the turrets up / down  left /right .  But not always .)

If you have had to crank a turret loads up or left or other to zero .Then you wont be looking through optical centre and the pressure on the internal adjuster springs can be either too much or little making the  adjusters of the internal optic that has the x hairs etched onto it .move from shot to shot .

 

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I had same problem with a Cz 223 on zero of zero after a lot of shooting and head scratching it turned out to be the scope I brought a new scope cost more than the gun never had anymore trouble with gun.

The scope is know on a Heanel sports 223 no problem with it at all the 

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I agree with those above “SCOPE” 

IT CAN JUMP IN & OUT OF ZERO 

Change your scope to something reasonably priced and make sure you use decent mounts as well 😃👍🏻
 

As for the mod damage it could be just down to the HMR power and the mod is a cheap mod or it has become slack at some point which results in clipping the side as your photos shows.

Buy a Wildcat or DM80  .17HMR SPECIFIC “REFLEX” type are best 

This is only my opinion after shooting for 40 yrs and a professional shooter “MARKSMEN” for 36yrs. Target shooting and vermin shooting for over 25yrs 

I am sure on here PW you will get the best help as we all like to help each other and we all have had issues like things like this over the years.

I wish you all the best and hope you get it sorted 😃👍🏻
I wouldn’t worry about cleaning the barrel to much neither just make sure the bolts & chamber end + mag is cleaned + the mod is checked for tightness when out shooting 😃👍🏻 Good Luck  

 

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