CZ452 accuracy, what is missing here ?

D

deffie

Guest
I really like to experiment and starting from a 452fs i've built a benchrest rifle, but actually after many tries i'm stuck at 240/250.

The rifle is in the 10.5 lbs category, i've made a custom stock starting from a draft, i bedded it and i gained some accuracy, i've installed a custom barrel tuner, i searched for the sweet spot and i gained some more accuracy, i tried many different ammo and i found sk standard the best for this gig.

In addition to this i removed the rear sight to lower the optic, i free floated the barrel removing anterior screwing point (which is the same piece as the rear sight), i tuned the trigger.

I was aware from the beginning that buying a benchrest rifle will have gave immediately better results in competitions, but immediate results are not the thing i'm looking at, I'm curious; I want to know what influences accuracy and in which way. So, reconnecting with the topic, is this the limit of the rifle ? and if yes what does make it ?


Thank you in advance,
Giacomo.
 
You should pinch some bullets from cartridges and push them down the bore to feel for tight or loose spots. Also check for choke at the muzzle and make sure the muzzle is located at the tightest spot in the choked section of the bbl.
 
Hi crb, I did the test you suggested and which i read about some times in the past but i never tried before, i got the bullet cutting a new cartridge and paying attetion to not damage the lead.

At first run the bullet came out with a greasy oily mixture on its head, it is about 300 shots from last clean.

However the test showed a loose spot of about 1/4 inch in length at about 4 inches from the muzzle, (seems) just before starting to tighten; the rest of the barrel seems constant.

:eek:
 
crb said:
You should pinch some bullets from cartridges and push them down the bore to feel for tight or loose spots. Also check for choke at the muzzle and make sure the muzzle is located at the tightest spot in the choked section of the bbl.
Click to expand...


Ray,

Can you please explain this process to me, I'm very interested. How do you "pinch" bullets? I've been wanting to "slug" my 6.5-06 barrel but don't know how, is "slugging" the same thing?

Thanks,
Med.
 
ultramagmed said:
Ray,

Can you please explain this process to me, I'm very interested. How do you "pinch" bullets? I've been wanting to "slug" my 6.5-06 barrel but don't know how, is "slugging" the same thing?

Thanks,
Med.
Click to expand...

I've removed a bullet from a cartridge, and i pulled it down into the bore with a brass cleaning rod without head, it is easy to go ahead, i can estimate a force of 3-5 kgs, also it becomes evident when you find a change of tightness as your hand jumps ahead when it gets looser and you have to apply more force when it becomes tighter.

Some reference (there is more):
http://findarticles.com/p/articles/mi_m0BQY/is_2_54/ai_n21175826/
http://www.surplusrifle.com/reloading/slug/pdf/slug.pdf

I'll repeat the test this evening after cleaning the barrel.

I've read that a change in terms of needed force may be addressed to a change in terms of smoothness of the surface; however, what i felt when doing the test is a big jump with complete loss of grip and I dont actually think its just a change of smoothness in the surface.

What to do ?
 
How loose is the chamber?

My CZ452 has a lousy chamber. If it had a true target chamber it might help. Might not too. I haven't slugged the barrell but why bother when it doesn't appear to have enough acuracy to get me started on trying to improve on it. Max
 
Max Shaffer said:
My CZ452 has a lousy chamber. If it had a true target chamber it might help. Might not too. I haven't slugged the barrell but why bother when it doesn't appear to have enough acuracy to get me started on trying to improve on it. Max
Click to expand...


Are you refering to the excessive diameter of it, ie excessive tolerance ?
I still didnt measured it but what should be the right diameter for a target 22lr ?

thank you,
Giacomo.
 
crb said:
Having the crown at the best possible spot is critical.
Click to expand...

I'm in trouble with technical english,
with "the crown" you are referring to muzzle-side chamber limit ?

And if yes, the right spot is about let the brass enter the chamber in the right measure ? Are you also taking in consideration freebore ?
 
I repeated the slugging test after cleaning and now the feeling is different, before i was able to feel repeatdly and with certaintly the loose spot as said in the previous reply; now i can only feel a tightening when arriving near the muzzle of a length of about 4 inches.

So, seems that the garbage of 300 shots affects the travel of the bullets and thats interesting to me because a couple of weeks ago during a match i started shooting the day after cleaning the barrel, and after 25 shots out of the target to "initialize the barrel" it made 5 10x with 5 mouches, the rest of the target was not good as this, in fact it ended with the same 237.

I dont know how much five perfect shots are able to tell that the rig is able to do it for an entire target...
 
You probably had some leading in the bore. What ammo are you using?

A lot of the top BR shooters do some sort of cleaning after every target.
 
crb said:
You probably had some leading in the bore. What ammo are you using?

A lot of the top BR shooters do some sort of cleaning after every target.
Click to expand...

I'm using SK Standard (Yellow).
 
A .22 target chamber

should leave rifling marks on a bullet that has been chambered and removed without fireing. Also the internal diameter of the chamber should not be so large as to allow the cardridge to be a sloppy fit. My CZ 452 has a loose fit on the cartridge and the cartridge barely touches the rifling. My 541S Remington has a smaller daimeter chamber and Eley ammo will be seated about .090 into the rifling. The Remington is a much better shooter than the CZ. There may be other factors involved but the centerfire benchresters say a good chamber is critaical. Max
 
I would clean the rifle very well and try some Eley Match EPS or Tenex EPS and see how much the scores improve. That'd be a start. I'd guess you can up the score 5 points a target or more using top notch ammo.
 
Deffie,

Without spending heaps of money I think the match chamber is your only chance to pick up a few more points. Here in Australia most of the 7lb 12oz rimfire benchrest rifles were Model 1's, Model 2's @ CZ452's (we don't shoot 10 1/2 lb benchrest here). The first thing we do is replace the barrel with a S/S match barrel, put it in a Benchrest style stock and tune the trigger or replace it with a Walther match trigger (gunsmiths job...works better on Model 1 Brnos but can be made to fit Model 2 or CZ452).
 
Steve Nash said:
Deffie,

Without spending heaps of money I think the match chamber is your only chance to pick up a few more points. Here in Australia most of the 7lb 12oz rimfire benchrest rifles were Model 1's, Model 2's @ CZ452's (we don't shoot 10 1/2 lb benchrest here). The first thing we do is replace the barrel with a S/S match barrel, put it in a Benchrest style stock and tune the trigger or replace it with a Walther match trigger (gunsmiths job...works better on Model 1 Brnos but can be made to fit Model 2 or CZ452).
Click to expand...

Thank you all for your replies, as Steve says the bad piece is the barrel, in fact i can feel again the loose spot, the slugging was faked by the cleaning substance, once the barrel dried i was able to feel the loose spot where before said.

I'd love to be able to change the barrel without throwing everything away, i also was having a nice homemade stock which i was proud of; unfortunately here in Italy you cannot change firing components without going thru a process of omologation which must be driven by a gunsmith and costs many money and time and no one does it, it is done sometimes by some custom shops for centerfire rifles (ie. >4000 eur stuff).

Actually i'm going to buy a brand new barreled action of an anschutz 1907 or 1913 and ill made the stock and tuning myself once again, at least i gained some experience and lost a little money :p

If you do have some suggestions based on your experience on the anschutz model to look for ill thank you, I've read somewhere, maybe here on BR Central, that a top shooter was not happy of the original anschutz barrel and replaced it with a benchmark, i'd love to have such possibility :(

Thank You,
Giacomo.
 
You must log in or register to reply here.
Back
Top