CZ455 .17HMR not holding zero very well... I don't think?

[Doric]

Hi All,

My CZ455 HMR normally shoots perfectly, 1 inch at 100 yards type accuracy with Hornady 17grn V-Max, all I can ask.
It has a Nikko-Stirling 4-12 x 50 on the front, I know it's not the best by any means but I was buying on a budget and the scope was easier to update in the future than the rifle.

This evening I went up and sat in a highseat, overlooking a cover-crop and fallow field with the view to shooting a few crows that have been kicking around and a short-range fox if it decided to show.

Anyway, to cut a long story short I had some accuracy issues the other day when I took it out for a bit of practice at a cardboard box (initially way off, brought it back on point and I put 15 shots in a 2 inch circle at 100 yards).
This evening, I got a bit bored and cold so shot at a few of the sunflower dead seed heads in the wild bird mix crop. Probably at 40-50 yards and probably 1.5-2 inches in diameter. I had a rock steady position but was missing them!!

I was a bit frustrated about this and started to think about the possible causes (below) If you can think of any others, or have any suggestions of how to remedy them then please do say!

• Action screws not tight causing wobble - everything tight.
• Scope mounts not tight? Nope, everything tight.
• Moderator? I have been taking my SAK mod on and off as it's shared with my .22RF, could that be it?
• I have definitely dinged the scope VERY lightly a few times when taking it in and out of the cabinet etc. Possible, but very light dings so seems odd...
• Ammo not being accurate. Seems odd as the rifle can shoot very straight indeed.
• Cheap Scope not holding zero properly? Always possibly but I'd like to think it can cope...
• No problem at all and it's me not pulling properly - the trigger is very 'creepy' and a trigger kit is on the cards.
• Wind - There wasn't any!
• Gun coming onto zero with a warm barrel. This is possible I suppose? But the HMR can't generate that much heat and this is probably v unlikely.
• Change in cleaning regime? I've never cleaned it and it's usually happy!

Bit of a random list, but before I go and buy a new scope or whatever I thought I'd open it up to you lot!

Thanks in advance... Happy New Year!

Have you checked the case necks? there is a lot of poor quality amo out there. Thats why I replaced my HMR.

 

[sunndog]

Sorry to resurrect an old thread but we get told off these days if we don’t use the search tool how many fouling rounds would you say it needs? I foolishly cleaned my .17hmr a couple weeks ago and have now put about 30 rounds through it but still can’t get any accuracy back, wondering if it needs a lot more to foul the barrel?

Mine normally takes about half a dozen. Are all the screws done up tight?

 

[Foxyboy43]

I have had my Cogswell and Harrison (CZ) .17 for about 3 years and have put a lot of rounds through it. A simple 3 passes with a (good quality) pull through as soon as I get home has been all I have ever needed to do and it is always spot on - in fact when I think about it the scope has not been adjusted since I first zeroed it. Nor incidentally have I ever noticed a miss with a shot immediately after cleaning so I am not at all convinced of the need for “fouling shots” - maybe I am just lucky?
The chambering is well known for barrel fouling and resultant loss of zero but IMHO a £20 pull through is all you need.

 

[Overlay]

Give it a good clean, re check and tighten any screws, moderator etc etc, find a calm place to re zero and shoot it back in at a 100 if there are any issues after that, start looking at your mod, ammo scope etc, might just need a bit of TLC
Keep to one proven ammo batch and a flat shooting range to keep all things equal
Good luck with it and keep us in the loop on developments

 

[sunndog]

I have had my Cogswell and Harrison (CZ) .17 for about 3 years and have put a lot of rounds through it. A simple 3 passes with a (good quality) pull through as soon as I get home has been all I have ever needed to do and it is always spot on - in fact when I think about it the scope has not been adjusted since I first zeroed it. Nor incidentally have I ever noticed a miss with a shot immediately after cleaning so I am not at all convinced of the need for “fouling shots” - maybe I am just lucky?
The chambering is well known for barrel fouling and resultant loss of zero but IMHO a £20 pull through is all you need.

Seems to vary a lot from rifle to rifle.
I pull a bore snake through a couple of times every 500rnds or so.
After a clean it goes from one hole groups to 2" groups and quickly back down again...dunno just its personality I guess.

 

[Tikkat3xl]

Mine normally takes about half a dozen. Are all the screws done up tight?

Was very accurate before I gave it a clean and haven’t touched anything while cleaning but to be on the safe side I have stripped it right down and re torqued everything, we shall see when I get a chance to zero

 

[sunndog]

Same batch of ammo?

 

[Friendly Boar]

Once I had similar with my 22. Cleaned it and back to super accuracy.

 

[Colonel Rimfire]

I don't have any real experience with HMR however, I messed around with centrefire for many years.

Firstly try a different batch of ammo

Then try get a good copper solvent and give it a long soak. I use KG12 big bore cleaner. If you can find anyone with a slender enough bore scope, ask them to take a look at the chamber and leade. You might have copper fouling or hopefully not the dreaded fire cracking.

Just to be sure, do the shoot one clean, shoot two clean, shoot three etc. etc.

I had the misfortune to own a few Nikko Sterling scopes they can lose zero for no apparent reason even the more expensive models and then fail to hold zero once reset, The tracking was inconsistent and it was basically junk.

Personally I would recommend a Hawke Vantage at minimum and a set of steel rings

Also invest in a torque driver most CZ's like 15-25 Inch pounds. Changing the torques settings is like zeroing you can achieve some brilliant groups by slowly adjusting the action screws.

 

[sharkbait]

A list as long as your arm of things to check that could be wrong!
A process of elimination!
The Joy's of rifle shooting

 

[Tikkat3xl]

Same batch of ammo?

Yes, same batch, was debating now that I’ve removed the scope and double checked for tight whether it would be worth giving it a second clean?

 

[sunndog]

Dont sound like a second clean would hurt anything at this point lol
Is this the first time you've cleaned the rifle and what did you do?

While the scope is off have you got another one to try?

 

[Tikkat3xl]

Dont sound like a second clean would hurt anything at this point lol
Is this the first time you've cleaned the rifle and what did you do?

While the scope is off have you got another one to try?

A pull through several times and yeah the first time (that’ll teach me)