CZ 452 - Accuracy problems and expectations

[NHR]

Greetings all,

Back when CZ brought out the 455 I decided to snag one of the last 452 Americans I could find in stock. It sat mostly unused except for the occasional squirrel hunt. I noticed that it never seemed to group quite as well as my 452 Lux. Last fall I had it cut to 18" and threaded for a can. As I shot it more I got frustrated with it and decided to try bedding the stock. This was my first attempt. I purchased a pillar kit and used Devcon. Two things went wrong:

1. I think one pillar is slightly misaligned. I can feel the rear action screw binding as I insert and torque it down. You can also see wear marks on it where it's rubbing against the pillar
2. I didn't use a good release agent and I pulled the action too early. The result was I found a large amount of the un-cured epoxy had stuck to the action. I was able to remove it, re-coat the action with a better release agent, and put it back into the stock though. The final result is that the bedding looks like open-cell foam in the stock. Rigid, but very porous.

Before redoing the whole thing I decided to test the rifle and see what it would do.

I tested 11 different types of ammo to try and find what the rifle would like. I fired 10 round groups at 50 yards and used Range Buddy to measure each group. For this initial testing I shot off of a front bag with no rear support.

CZ 452, 50 yards, front rest
Group	Ammo	Extreme Spread	Mean Radius
1	CCI Blue	5.4	2.07
2	CCI Blue - No can	6.22	2.59
3	Aguila HV	3.74	1.11
4	Ficocchi SSHP	3.2	1.03
5	Aguila SV	2.91	0.99
6	Rem Target	3.24	0.93
7	Geco - Bolt Action	1.62	0.63
8	Geco - Semi Auto	2.08	0.75
9	Federal GMM	2.17	0.7
10	CCI 45gr HP Suppressor	5.66	1.15
11	Eley SSHP	2.34	0.72
12	Win SSHP	3.18	1.05

I was pretty surprised, and disappointed, at how poorly the rifle grouped with typical decent ammo. Still, I decided to buy more Geco "Bolt Action" ammo and experiment with action screw torque and also test if the suppressor had any effect. All groups here were shot with a bipod and rear bag.

Front Torque	Rear Torque	Suppressor	Extreme Spread	Mean Radius
20​	20​	No	1.99​	0.61​
22​	22​	No	3​	0.79​
22​	22​	Yes	4.24​	1.29​
25​	25​	Yes	4.06​	1.09​
25​	25​	No	3.21​	1​
27​	27​	No	3.05​	0.97​
27​	27​	Yes	3.74​	1.12​
30​	30​	Yes	2.59​	0.86​
30​	30​	No	1.92​	0.7​
32​	32​	No	4.31​	1.24​
32​	32​	Yes	2.95​	0.86​
15​	15​	Yes	2.34​	0.66​
15​	15​	No	2.16​	0.69​
17​	17​	No	2.56​	0.91​
12​	12​	No	2.52​	0.69​
15​	15​	No	4.6​	1.17​
15​	17​	No	3.26​	0.85​
15​	15​	No	1.72​	0.27​
15​	15​	Yes	1.91​	0.73​

At this point I'm still pretty disappointed. The best performance seems to be at 20 in-lbs followed by 15 and 30. Overall there was no change from my previous test in the best tightest group. The suppressor typically increases the group size, but not always, and I would probably need to fire multiple groups to confirm that.

So what does this all mean? Do I have a turd of a rifle? Should I re-bed the action in the stock? Should I ditch the stock and put it in something more rigid like a Boyds varmint? I'm cautious about dumping too much money into this thing when I could just go out and buy a T1x or 457 and (probably) have better luck. At least with a new 457 if it has a turd barrel I could replace it easily.

Is there anything else I should be experimenting with? Any other potential causes of bad accuracy? Or am I expecting too much from this thing?

 

[Near miss]

I think the barrel is bad.

You had good intention in fixing it but with a good barrel and appropriate torqued screws a certain level of accuracy should be achievable.

How does it do with SK and Lapua ammo?

 

[krw]

What is mean radius?

 

[jakelly]

If you’re seeing that much dispersion from adjusting torque on the action screws, you’ve got something jacked up. Rebed the thing. Buy some premium ammo (Eley, RWS, and Lapua) don’t keep switching ammo types. After switching ammo type, let the barrel settle in with 20 rounds or so before you start measuring groups. Shoot 5x5 and check the agg @50 should be below 2 MOA. If it isn’t I’d check to make sure that barrel didn’t bellmouth when the threads were cut. CZ chokes their 22 barrels, you might have ruined it.

 

[NHR]

I think the barrel is bad.

You had good intention in fixing it but with a good barrel and appropriate torqued screws a certain level of accuracy should be achievable.

How does it do with SK and Lapua ammo?

I haven't tried it with any true premium ammo. I don't have any on hand but I wouldn't be opposed to buying some for a fair test.

What is mean radius?

Mean radius is a helpful tool for evaluating groups. Calculate the theoretical center of a group and then measure the radius, or distance from center, to each shot. The average of those radii or distances is your mean radius. When you compare your mean radius to your extreme spread you can easily see if that group had flyers that blew it out or if it just had large dispersion.

If you’re seeing that much dispersion from adjusting torque on the action screws, you’ve got something jacked up. Rebed the thing. Buy some premium ammo (Eley, RWS, and Lapua) don’t keep switching ammo types. After switching ammo type, let the barrel settle in with 20 rounds or so before you start measuring groups. Shoot 5x5 and check the agg @50 should be below 2 MOA. If it isn’t I’d check to make sure that barrel didn’t bellmouth when the threads were cut. CZ chokes their 22 barrels, you might have ruined it.

What do you mean by bellmouth and "choking" a 22 barrel? Do you mean they literally reduce the diameter of the bore at the muzzle? Is there a physical of visual inspection I can do?

I agree I think I should rebed the action. I don't have anything to lose but time at this point. My gut says that if I see decent clustering with certain types of ammo that it may be a stock/bedding thing.

One other observation:
I've noticed the rifle rings like a tuning fork. Whenever I shoot off a bipod I can hear the rifle "ring" with each shot. If I firmly grasp the forend in one hand and tap on the muzzle it'll ring, and if I firmly grasp the barrel or can and tap the stock it'll ring. You can feel both the stock and barrel resonate when doing this. Not sure if that's normal or just much more noticeable with a suppressor.

 

[Merlin O]

GIGO - garbage in and garbage out.
Garbage ammo - garbage accuracy.
But a good/even decent barrel would do generally better than what you are seeing here IMO.

Added edit. Checked the crown?

 

[NHR]

GIGO - garbage in and garbage out.
Garbage ammo - garbage accuracy.
But a good/even decent barrel would do generally better than what you are seeing here IMO.

Added edit. Checked the crown?

Understood on the ammo. I'm not expecting match-grade results from sub-par ammo, but I am expecting better than 3MOA.

I'm definitely no expert on crowns but I don't see any obvious problems here. Please tell me if you disagree.

 

[jakelly]

Yes, choke- the diameter of the bore decreases toward the muzzle end. You can google slugging your barrel, which will expose bellmouthing and the tightest spot in the bore. You can also buy pin gauges to insert into the muzzle end, but I would just slug it.

 

[NHR]

Thanks, I Googled and learned.

I slugged the bore in both directions.

From the muzzle: tight getting it started and then it almost immediately opened up and was easy to push through. I encountered a slight increase in resistance just before the chamber.

From the chamber: similar experience, but overall easier to get started. I could push it easily until ~ 1 inch before the bore and then it tightened up.

Both slugs pulled out a lot of green/blue wax. I'm assuming this is from the CCI clean ammo I've been shooting. I wonder if that had a negative effect...


Both slugs measured 0.2205 inches

 

[jakelly]

Using a fresh non-plated slug, map the the bore from chamber to muzzle. You don’t want a tight spot near the chamber. You also don’t want the bore loose within three inches of the muzzle. Specifically check if the bore gets loose under that threading at the muzzle. If it is tight right in front of the chamber you might have to lap it a (very) little. The idea is to keep the projectile deformity to a minimum early in the launch and the tightest (more deformity) shortly before the projectile exists the muzzle. You want the projectile stabilized, not ricocheting down the tube. And yes, don’t shoot anymore blue crap coated bullets.

 

[jakelly]

You don’t want your rifle ringing either. That bedding is probably introducing stress rather than relieving it. I would fix that ASAP.

 

[NHR]

I decided to redo the bedding on the stock. I dremeled out the old stuff and did a much better job this time. Glued the recoil lug in place and bedded that first. Once I had that secured I did the rest of the action/stock:

I was able to retest using the same Geco bolt ammo and I'm now getting 1.75 MOA on the high end and just under 1MOA on the low end. This is indoors at 20 yards. CCI std is pretty meh at 2-2.5 MOA.

Eley SSHP is pretty consistent around 1 MOA. I need to order more as I only have half a box left. I'll also order some other Eley varieties to see how they do.

I think I'll keep the rifle and leave it alone other than getting a scope with adjustable paralax. Its been hard has hell shooting half decent groups with fixed 100yd paralax. Its plenty accurate to plink with and pop squirrels.