Canadian Airgun Forum

What experience have others with bolt shims for improving accuracy?

We shoot CZ457LRPs and I see that Reliable Gun & Tackle (Vancouver) have a set of shims @ $9.99 with free shipping by first class mail.

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Slavia 618 .177
Webley Senior .22
Jelly SUPER 4.5 mm
Webley Viscount .177
Kral Mega Marine Walnut .22
Artemis PP750 .22
FX Streamline .22 walnut
FX Streamline .22 composite
FX Dynamic 500 .22

I would get the kit, just out of curiosity. I have heard of shimming Ruger 2-piece bolts of the M77/.22.

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Best Wishes
Daryl

I can see the shim, in concert with a headspace rim gauge in .22 to segregate cases based on headspace,
would be better than just the "shim" kit by itself.
Individual headspace is VERY important. Changing shims in the bolt, changes the headspace - that's it.

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Best Wishes
Daryl

I have a rim thickness gauge, for 40+ years from back in the target days, so set that way.

I'm just wondering what success people have had with headspace changes in the 457s, especially the LRP or other match chamber models.

_________________
Slavia 618 .177
Webley Senior .22
Jelly SUPER 4.5 mm
Webley Viscount .177
Kral Mega Marine Walnut .22
Artemis PP750 .22
FX Streamline .22 walnut
FX Streamline .22 composite
FX Dynamic 500 .22

Many .22LR shooters hope to improve accuracy performance by adjusting the headspace. As Bill Calfee, the noted American .22LR benchrest rifle builder says, as long headspace is safe, it has little to do with accuracy performance. That is always the product of a good bore and good ammo. Bulk and high velocity .22LR ammo is well-known for inconsistent performance and nothing can be done to improve its accuracy. Use at least entry level match ammo such as SK or Eley Club or RWS Club.

CZ sets the headspace for .043" as per CIP specifications (SAAMI specs call for the same). Unless the headspace is not .043" there is no need to adjust it. Check with a go and no go .22LR headspace gauge to see that headspace is neither too small or too great. The only way to measure headspace reliably is to use graduated headspace gauges and these are not readily available.

Sometimes headspace is easily adjusted with the use of bolt shims. On a CZ 457 or CZ 455 -- which both have user removable and changeable barrels -- the best way to adjust headspace is with the use of barrel tenon shims. These are included with some aftermarket drop in barrels such as Lilja.

I think we all suffer with the need to "tinker syndrome".....

Seriously, the CZ457 has a precision rifle bolt action with the consistent chambering installed to the proper headspace specs. You should be able to hear weak fires or "light strikes" causing issues. My first thought would be to start using premium ammo and stay away from the dirty bulk pale budget ammo.

I'm not saying all budget ammo is bad nor am I saying premium ammo is the best......Experiment with many brands and find the one you really like to use. I have found "high power" premium ammo has proven to be not as accurate however, you can purchase premium lower power as well.

My brother ended up inheriting the 1960's Brno bolt action 5 round mag rimfire and I have yet to find a rifle today that can even come close to this hard hitting beast. I love my Ruger but it ain't no Brno......Perhaps I need to find someone with a CZ457LRP and find out for myself.

Budget ammo is not accurate because it's made to a minimal quality level which is that it should go bang when the firing pin strikes. It's not made to be accurate. That's why it's inexpensive.

It's a myth that a rifle will "like" a particular brand or make of ammo. That's not how it works. It's important to understand that all match and entry level match ammo will vary in performance according to lot. In other words not all lots of Tenex will shoot equally well.

There are a bunch of silhouette shooters here using CZ's or older BRNO's.
I have not heard of 'adjustments' being needed to them.
These guys shoot both CF and RF silhouette. We've hosted the nationals twice that I know of
both RF and CF.

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Best Wishes
Daryl

Without getting into the "science" which I don't understand anyways but, here is a good link explaining powders and temperatures etc. How many times we go out to shoot and have a "great day", was the temperature and humidity at peak conditions, or were we just on our "game" that day?

https://www.gunsandammo.com/editorial/t ... der/389257

We used to load most of our ammo back in the day and my dad seemed to be the "scientist" in all. I swear he could smell and taste bad powder? Primers were another thing to consider as well......

Since we're talking about rimfire, how many of us keep a 100 rounds in our truck? Understandably, if shooting match this should be understood not to do so, or is it?

I'll go along with this up to a certain point, but not quite as far as an "ironclad rule".
Got quite a kick out of people chasing lot #'s in the mid to late 90's. (Anyone remember the old Federal GMM UMB 90?)

And then of course there's the Pandora's box concerning Green Tag. I was never able to find a lot # that was consistent for me in any of my 2 match chambered bbl's.

I did find almost reasonable consistency across lot #'s with a choice that's still a little hotter than usual- Lapua Polar Biathlon was reasonably tight across various lots.

These days, since I'm no longer looking for the scoring plug certified single hole, I do well with the much more affordable CCI mini mag- which still shows little variance after years of hunting with it... not really competition grade in the sense of the word, but capable of harvesting small game the way I like to at sometimes surprising distances.

-D.S.

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"Ain't no half-way"
-S.R.V.

My sporter Anschutz prefers Winchester 555 for some reason. Go figure- and it's consistent at 44 yards.
That is the furthest I have tested it. It also likes the 1,445fps Browning HP's.
My current favourite grouse rifle.

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Best Wishes
Daryl

That's a nice looking rifle. I came quite close to buying the C.I.L. version way back when, but found the comb drop a little low for scope use...

How does your's line up with your eye?

-D.S.

_________________
"Ain't no half-way"
-S.R.V.