Vexing problem with my CZ .223 and assignable cause. Range Report Added.

Fitch

Fitch

New member
The accuracy of my CZ527 .223 has been remarkably good up until a few weeks ago when it began to fall off. I suspected it was deteriorating based on where I was hitting ground hogs so took it to the range. Three shot groups had opened up from around 3/8", which it did group after group, to noticably over an inch. Not good.

I swapped scopes, same thing. Borrowed my buddies borescope to peer in the barrel. Muzzle crown looked a little rough,
oo I took the action out of the stock to re-crown it and was surprised to see the rear pillar fall out! It had some how gotten loose in the stock, it was longer than the wood so the action screw was clamping the tang to the bottom metal but not to the stock. Bottom line, the tang was effectively unsupported and free to move around. Not a feature.

The CZ527 only has a rear pillar as it comes from the factory.

I was almost relieved to see this because it looked like it would explain what was happening, "and" I could do something about it. Finding a plausible and fixable cure for a vexing problem feels pretty good truth be told.

I bedded my CZ527 Hornet earlier in the summer. I made it two pillars (I clanged the can with the roll pin because it wasn't going to glue in well), hogged it out from the front of the receiver to the front of the mag well and after gluing in the pillars with the rear pillar slightly proud of the stock wood, epoxy bedded the front of the action. That worked well. The Hornet is shooting 1/2" groups one after the other.

Note, the front pillar has to be long enough (but not more than .005 to .010 longer) that the bottom metal/magazine well doesn't bottom on the receiver - it's better to have the glued in front pillar as the tallest pole in the tent so to speak.

So I am in the final stages of doing the same thing for the .223. I re-crowned the barrel just to be sure and the crown looks really good now. I made it two pillars, glued them in yesterday, and this afternoon went ahead and epoxy bedded it. The action is in the stock with the epoxy curing. I'm hoping to get it to the range late this week to see if that cured the problem.

If you have a CZ527 I hope it is shooting well, but if it isn't, you might look for a loose rear pillar.

I'll post a range report after I shoot it.

Fitch
 
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That rear pillar is in there loose. That's the way these rifles come. I also staked mine in with epoxy when I bedded my 527. I also thoroughly relieved the barrel channel to make sure the barrel was free floated. The gun is an excellent shooter. I have nothing but praise for these rifles. Could you possible be getting copper fouled? Just wondering. Dave
 
I believe mine is shooting poorly because it fell out of the Polaris Ranger while checking salt boxes & the rear tire ran over it !! OUCH !!!!!!
Mark
 
Originally Posted By: mark shubertI believe mine is shooting poorly because it fell out of the Polaris Ranger while checking salt boxes & the rear tire ran over it !! OUCH !!!!!!
Mark

I hate it when that happens!

Dave,

Good thought ... I've had it happen with other rifles, but it think I've ruled it out this time. I cleaned it till there was nothing but bright steel in the bore (I had the bore scope here at the time). Then gave it three shots to foul, let it cool and fired my groups. I don't clean it between trips to hunt GH, it shoots about an inch off for the first shot, sometimes first two. It seldom goes 20 rounds between cleanings though, and when it was shooting well, that didn't bother it. One of the good things about my two CZ rifles is the quality of the bores. They are the best factory barrels in my gun safe by a significant margin.

Mike,

Another good thought - I've had that happen too. I am using the CZ rings (the rifle is a CZ527 American sporter). They were installed with the rear ring indexed by the notch in the mount dovetail (which is machined into the receiver) and both were torqued to 25 in-lbs. The ring's clamp screws (4 per ring) were torqued to 20 in-lbs. I can say the ring to base clamp screws were nice and tight when I loosened them to take the scope off. I just checked and the scope ring clamp screws are still tight (don't move at 20 in-lbs of torque).

Thanks for the additional ideas.

Fitch
 
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If it just seemed to magicaly have a problem you can't see a reason and it was good before then send it in to cz if its still under warranty! they may still work on it for free even past warranty, they have done for people before.
 
Originally Posted By: TripleDeuce660If it just seemed to magicaly have a problem you can't see a reason and it was good before then send it in to cz if its still under warranty! they may still work on it for free even past warranty, they have done for people before.

It developed the problem over a summer of ground hog hunting but it's a moot point now. I took it to the shop.

I recrowned it,

NewCrown-RS.jpg


made it two new brass pillars and bedded it.

I milled a slight draft angle on the front of the recoil lug "just-in-case"

DraftAngleMilledonfrontofrecoillug-.jpg


and hogged the stock out from the front of the receiver to the front of the mag well which is where I put the bedding compound. The front pillar has just been epoxied in place in this picture, so was the rear pillar but it doesn't show in this picture. It was all fit up and the pillar lengths set before the stock was hollowed out.

FrontPillarinhoggedoutstock-RS.jpg


I think CZ will probably consider it's "my" rifle now which is just fine with me.
grin.gif


I think they make great rifles. I also enjoy working on them now and then when I get a chance.

I'm not a gunsmith, I am a hobby machinist, have been for just short of 60 years, so I fit and chamber my own barrels.

I'll be taking it to the range in the next couple of days to see if that fixed the problem. The rest of the rifle looks good - chamber throat and leads look really good.

Fitch
 
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Yeah, I'm curious too on the real issue here. The comment above on the rings/bases was from a dropped Rem 700 with apparent "ok" rings/bases, but when nothing else worked out, we changed them, and bingo - back to original accuracy. Couldn't detect movement, but it musta been there somewhere?!?!? Let us know what you find out.
 
I got it to the range today. I had some of my normal ground hog load (40g Nosler BT seated 0.020" off lands, 28.0g of AA2460, Win brass, CCI400 primer) to use for seeing if it shoots better. The scope is the Bushnell 3200 Elite 3-9x40 that has been on the rifle since new. (I'm not happy with the scope but that's another story for another day.)

All of the targets below were fired on the 100 yard range at Shippensburg Fish and Game.

This is the "before" picture (groups fired 09-23-2009):

CZ52722340gNBT28gAA2560.jpg


This is the "after" picture (today, 10-02-1009).

223isback.jpg


The rifle had been cleaned to a bright silver bore with no copper left in it prior to a borescope examination. S1 was the clean bore shot. I moved the scope right 5 clicks. Second shot was S2. Moved the scope left 2 clicks and fired 1 shot, liked where it hit and fired 3 more. I hesitated after the third 3 (fifth total) but went ahead and fired the 4th, then stopped. I don't like to shoot more than 5 or 6 in a row out of a sporter.

I'll take it back for more testing next time I'm at the range, but at the moment it looks like it's back in commission. It is at least shooting a lot better than it did before.

Fitch
 
I have had some groups crop us very similar to your before pictures latley. Do you think it was the crown, bedding or a combination of both that caused it?
 
Originally Posted By: ACLakeyI have had some groups crop us very similar to your before pictures latley. Do you think it was the crown, bedding or a combination of both that caused it?

Excellent question. I have a little data that might shed some light on it.

I've seen something similar five times this year. The first was my Savage Model 10 .243 which was shooting 2" groups after a couple of years of trying to find a load. The second was my Savage LRPV 9" twist .22-250 which went from dime sized groups to 1" groups after about 2500 rounds. The third was my CZ527 .22 Hornet. The fourth was my brother in law's Winchester Model 70 Coyote (.22-250) which, after spending most of last summer trying to find a load, was shooting 1-1/4 to 1-1/2" groups with the best load we could work up. The fifth was the CZ in this thread.

The two Savages were what got me into doing my own barrel work - I'm retired and I had, serrendipitously, an excellent lathe for doing it and a Bridgeport clone mill, and several decades of amature machinist background - so I figured why not? But I digress.

In the case of the Model 10 Savage an examination with my friend Rich's borescope showed the bore had a section about 4" long 6" back from the muzzle that looked like an annular file. Big sharp chatter teeth that started above the top of the lands and actually dug into the bottom of the grooves. Boy was that ugly. The chamber was also not quite symmetrical in the throat and the chamber had big galling marks around it (which would have accounted for all the hard extractions). Rich also happens to be a real gunsmith, and spent some time with me explaining what I was looking at, the significance of it, and then let me look at some of his recent work with Shilen, Krieger, and Bartline barrels (mostly chambered in .338 Lapua). His barrels looked real darn good! My Savage barrels, not so much.

In the same borescope session I got a look at the throat and barrel in my LRPV. It had been a good shooter but the reasons for the deterioration were obvious - the chamber throat looked like a mid desert summer dry lake bed. About an inch and a half of thermal shock erosion scales.

I decided to spend last winter teaching myself to chamber and crown barrels and to bed rifles so I could fix them myself. I did that. Winter is shop season.

A friend of mine who also does his own barrels had a used A&B (Adams and Bennett) barrel - sexy looking thing, stainless with fluting and all. It was chambered in 6mmBR. He wanted $40.00 for it. I figured it was a good one to practice on. I wanted it to be chambered in .243 so I sawed the chamber off and rechambered it as a .243 and recrowned it which left it 22-3/8" long. While I was at it, I trued the front surface of the receiver. When I got to shoot it this spring it was much better, groups went from the previous ~ 2" to around an inch and a quarter. Realizing from my engineering career that accuracy problems tend to combine as the square root of the sum of the squares of their individual combinations I knew I'd made a big improvement but there was still at least one big contributor left, so with nothing left to try (I'd already swapped scopes and rings) I ordered some AcraGlas gel, watched Darrel Holland's video on bedding, talked with Rich about bedding for half an hour and got some good tips, and bedded the rebarreled Savage. When I was done I took my prospective 55g NBT ground hog load and my planned 95g NBT deer load to the range and shot them. The rifle was zeroed for the 55g load when I shot these groups which are more or less typical:

I shot five 5 shot groups with the 55g load, the accumulated group average size over the 25 rounds was just under a half inch. This group was typical at 100 yards.

243with55gNoslerBT-A.jpg


I shot this group with the 95g NBT at 100 yards:

243Deer95gNoslerBTIMR7828Load-A.jpg


These one at 300 yards:

24395gBT300yards-A-C-A.jpg


I shot a lot of others but this is already a long enough post with out them.

The LRPV barrel had a small issue on the crown in addition to having the throat shot out, seen here:

Crown-3.jpg


I recrowned it and it shot slightly better but it was clear I needed to rechamber it, so I did. While the barrel was off the receiver I trued the front receiver face. I also trued the receiver for the Model 10 which is shown in this picture on the mandrel in the lathe.

SetupOnMandrel-RS.jpg


After rechambering and recrowning it went back to being a 3/8 MOA rifle. I think it might shoot even better if I skim bedded it on the aluminum bedding block so I plan to do that this winter.

Borescope examination of the bore in the winchester Coyote showed it to have a good barrel, good chamber and throat, and a pretty bad crown right from the factory. The crown had little metal lips coming out of the muzzle that weren't in any way symmetrical. In the case of the Coyote, after spending last winter learning about chambering and crowning I recrowned it first. The groups went from about 1-1/2" to ~1". This is the picture I sent my brother in law after crowning and before bedding:

CoyoteGroup.jpg


Then I bedded it by making it two pillars and bedding the front of the action from the front of the receiver to the front of the magwell. Like the CZ it's a Mauser action, square with an integral recoil lug. After bedding it, it shot this target during the first range session and sent my brother in law this picture:

Gregsrifleafterbedding-A-An.jpg


He is pretty excited - he is coming down this week to pick up his rifle to go coyote hunting this winter.

The CZ527 Hornet, which I did before the CZ527 .223 in this thread was the prototype for how I reworked the Coyote and the CZ527 .223. The results weren't quite as spectacular as the .223, but the Hornet did get noticably better after crowning and bedding.

So to your question.

Based on my very limited experience "fixing" rifle accuracy problems over the last few months, I think it takes the whole rifle system being "right" to shoot small groups. If the bedding is perfect and the crown is screwed up, it won't shoot any better than the crown will perform. The crown becomes the tallest pole in the tent.

If the barrel is perfect, chamber is dead nuts, crown is perfectly orthogonal to the bore centerline at the muzzle, crisp sharp perfect edges, and the bedding is poor, it won't shoot any better than the bedding lets it. Same for ammunition - it needs to be optimized for the rifle and consistant in performance to shoot small groups.

If everything is pretty close to "right", and the shooter does his part, the results can be pretty spectacular. I did not expect the CZ in this thread to shoot as well as it does, but it did, and does, and I'm pretty happy about how it turned out.

For my hunting purposes (YMMV), groups in the quarter to half inch range are plenty good, and frankly they aren't that hard to achieve. I'm basically a home shop machinist with just under a year of fussing with rifles to make them shoot better. I looked in the barrel of the Model 10 and the LRPV almost exactly one year ago this month and discovered the challenge. After the winter of study, making tooling for the lathe, making a barrel vise and an action wrench, over the summer I've been successful in getting at least 1/2 minute Hunting accuracy out of 5 rifles which were shooting 1 to 2 minutes before I started. And shooting 24 ground hogs DRT with 24 shots to go with the cirriculum.

Am I having fun? Oh yeah!

Fitch
 
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Very good information, thanks for the time to put it together.

You mentioned you bedded the Savage, did it have a plastic stock and if so how did the bedding process go?
 
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