Corbon round stuck in CZ75 barrel


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freewheeling
April 3, 2004, 01:47 AM
I loaded a magazine of Corbon 9mm+P 115gr. JHP in a CZ 75B and racked a round. When I went to unload the weapon the round in the chamber wouldn't come out. It was stuck, and I couldn't pull the slide back. I eventually disassembled the gun and pulled the round out of the barrel with a pair of pliers. These Corbons are sort of a strange shape and I'll probably nut use them in my CZ from now on, although I plan to use them in my Kahr P9. Anyone else had this sort of problem? What's the cause?

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Preacherman
April 3, 2004, 02:25 AM
How many rounds have you put through that CZ? The reason I ask is that some of them have reportedly had problems with a very short chamber. The Cor-Bon round (and some others) has its bullet seated fairly far out of the case. It could be that in a short chamber, the bullet enters the rifling grooves and "sticks" there, rather than having enough freebore in the chamber to seat the round ahead of (but not touching) the rifling.

If you've fired plenty of other ammo through your CZ without any trouble, this probably won't be a factor. However, if your CZ is fairly new, this might be worth checking out. Try chambering a number of different rounds and see if you can duplicate the problem with other brands. If so, time to send it back to CZ to have the chamber reamed out slightly.

freewheeling
April 3, 2004, 07:33 AM
How many rounds have you put through that CZ?

Probably about 500 rounds. This is the first time I've ever had such a problem. I tried just pressing a round into the chamber with my fingers after removing the barrel from the gun. With the white box ammo I normally shoot, and with the hydrashock ammo I sometimes use as a defense round the round just goes in to its full depth and comes back out without any binding. In fact, pushed all the way in I can still move the bullet side to side a little. It has some "play." With the Corbon all of the rounds bind or stick in that last 1/32nd of an inch. Interestingly there's still a little play at the base of the round, so it must be binding toward the front. Where the other bullets begin to taper gradually immediately forward of the case the Corbon bullet is more "angular," remaining straight for 1/16th of an inch or so before sharply tapering. I don't have any problem using the Corbons in my Kahr P9.

I should probably take up this issue on the CZ forum, because I think you're right that the chamber is a little too short.

Walt Sherrill
April 3, 2004, 10:08 AM
Problems with a "short chamber" is NOT a common problem with 75Bs. I've only heard of it once, and have been participating on the CZ-Forum for several years... and we have over 3,000 registered users there. (The one time I heard of it, was with a P-01, which is a shorter barrel of a slightly different design [Compact size, with one, not two, locking lugs.])

COR-BON, on the other hand, has had its problems, in the past, with quality control. That may NO LONGER be the case -- but I've personally encountered it twice.

I don't use Cor-Bon, anymore, and know of several others who have done the same.

pauli
April 3, 2004, 10:42 AM
sounds exactly like the problem another guy had a week ago...

freewheeling
April 3, 2004, 10:43 AM
But again, Walt, the rounds are fine in my Kahr. It's clearly the shape of the bullet, that simply doesn't taper so encounters the end of the chamber.

I guess the question is, do the bullets lack an appropriate geometry, or is the chamber too short? Must guns load and fire these rounds OK, I should think, or they wouldn't sell very many. Do other CZ owners have the same problem? Are there other rounds out there with this "angular" taper, that might cause probems?

For now I'll just use the Corbon in my Kahr and the Hydrashoks in my CZ, but...

Tim Burke
April 3, 2004, 10:48 AM
Similar thread here (http://www.thehighroad.org/showthread.php?s=&threadid=73200). I note this guy initially had a problem with a Cor-Bon round, but subsequently reproduced it with a PMC Starfire.

freewheeling
April 3, 2004, 11:14 AM
Similar thread here. I note this guy initially had a problem with a Cor-Bon round, but subsequently reproduced it with a PMC Starfire.

OK, I'd say that if the gun fails to load severy common rounds properly then the chamber is being manufactured too short. Is it sacrilegeous or something to say that? Is CZ willing to publish a list of rounds that are incompatible with their gun? It sounds like one of those Microsoft "features," to me.

Ankeny
April 3, 2004, 11:27 AM
Here we go again. In my opinion, run a reamer in the tube so you never need to worry about the problem again.

Badger Arms
April 3, 2004, 01:07 PM
I can't follow this thread. Here's the nomenclature:

A ROUND is a case with a live primer, powder, and a bullet.
A CASE is the cylindrical brass part with the hole for the primer on one end and a bigger hole at the other end for the bullet.

I'm assuming that the case is sticking in the chamber. If it has only done it once, it could be a number of things but isn't necessarilly the fault of the ammo or the gun.

CZF
April 3, 2004, 02:11 PM
As Walt will probably tell you also. CZs are tested at the factory with
S&B FMJ ammunition.

Using other ammo in CZs is possible, but the guns are really designed for ball ammo of a certain length.

You might have read the same problem in Combat Handguns where
they tested the P-01.

I have shot Cor-Bon 115 gr. +P in my older CZ75s, but never tried
it in my P-01.

pauli
April 3, 2004, 06:38 PM
badger, it sounds to me like it's the actual bullet getting stuck, not the case.

freewheeling
April 4, 2004, 03:04 AM
Badger:

I think I've tried to cleave pretty closely to the nomenclature you suggest.

I'm assuming that the case is sticking in the chamber. If it has only done it once, it could be a number of things but isn't necessarilly the fault of the ammo or the gun.

Nope, it's the bullet that's sticking. Seems to be plenty of room around the case.

Badger Arms
April 4, 2004, 03:14 AM
Hmmmm, short chamber, lead 'ring' in barrel that grabs the bullet, or something WICKED. I'd take it to a gunsmith and have him run a finish reamer into the chamber by hand. That should tell you what the problem is. Have you shot lead bullets through it? Did you buy the gun new, or used?

Tim Burke
April 4, 2004, 08:36 AM
Denis Prisbrey, New CZ P-01 Police Compact, Combat Handguns, June 2004, pp46-52.

He reports this problem with Speer 124 gr Gold Dots.Trying several other Gold Dots from that box and another one led me to the conclusion that the chamber is too short to work with that particular bullet profile. A call to CZ USA to discuss the matter followed, and I was told that there were some CZ 75s a while back that had the same problem, none have been reported with the P-01 as far as the rep knew, and CZ USA would correct the chambers on any P-01s with similar problems under warrantee.

Lobotomy Boy
April 4, 2004, 11:26 AM
This whole thread has given me pause to think about quality control at CZ. Maybe I'll stick with the German, Swiss, and American manufacturers.

freewheeling
April 4, 2004, 12:36 PM
CZF:

As Walt will probably tell you also. CZs are tested at the factory with
S&B FMJ ammunition.

Using other ammo in CZs is possible, but the guns are really designed for ball ammo of a certain length.

Unless the gun is being manufactured only for a specific application that always and only uses ball ammo then CZ had better wake up and smell the coffee pretty quickly. They're hip deed in the consumer self-defense market and I can't imagine what sense the above manufacturing protocol makes in that context. Can you?

Again, it just doesn't seem likely that CZ would follow Microsoft's lead and provide a list of ammo that's "compatible" with their firearm, unless they were aiming at some sort of niche market.

I think I'll contact CZ and see what they have to say. Looks like I may have to ship the gun (Or possibly just the barrel?) to have it reamed, or perhaps they could just send a replacement barrel that's reamed with a slightly longer chamber. The additional length that's required is probably between 1/32nd and 1/64th inch. It's not much.

Tim Burke
April 4, 2004, 01:42 PM
Looks like I may have to ship the gun (Or possibly just the barrel?)
The next line in the article I cited stated that they needed just the barrel, and a single round of the offending ammo.

Zak Smith
April 4, 2004, 02:06 PM
All my CZ's - four in the household - exhibit this behavior. They are short-throated for whatever reason.

You're supposed to test-fire all self-defense guns with the ammo you want to to use to make sure they run with it, right? Jamming the bullet into the rifling so the slide won't retract is a big hint you might want to try some other ammo.

Anything with a straight "ogive" portion like the 90gr Gold Dots or a longer straight portion like Hornady XTP's is going to have this problem in CZ's when seated to a normal OAL of 1.120 - 1.140".

The loads I've had much success with are: S&B, Winchester white-box, Dynamit Nobel GEKO, factory Speer Gold Dots, Proload -- which is everything I've tried. Bullets with work when seated out to 1.150" include West Coast plated and Gold Dots. Precision Bullets (coated with some black poly stuff) had to be seated much shorter. 90gr Gold Dots (intended for .380Auto) had to be around 1.100". XTP's had to be seated short.

-z

Zak Smith
April 4, 2004, 02:10 PM
With regard to Gold Dots in handloads, I found that they would bind in the magazine before they would get stuckin the chamber. I did an experiment where I tried different OALs to determine what the critical length was. Using the 147's, they would stick in the chamber at 1.173" (which is too long for mags), chamber OK at 1.165" (would bind in mag), and run okay at 1.156".

I never had a problem running 124gr GD's at 1.147".

-z

rbernie
April 4, 2004, 02:18 PM
Freewheeling - here's some background info for you:

Every rifled barrel has to start the rifling SOMEWHERE just past the end of the chamber. Start it REAL CLOSE to the end of the chamber and the firearm will often be mo' accurate than it might have otherwise been. Start it a ways past the end of the chamber, and the firearm will be more pressure-tolerant than it might otherwise have been. There is no universal standard for this - it's a design spec that each manufacturer sets for their own purposes. It is usually considered ideal to have the bullet just touching the rifling (but not pressed into it) when the breech is closed. By the way - the gap between the end of the chamber and the beginning of the rifling is called 'freebore' or 'leade'.

Now, picture a standard 124gr hardball bullet, and then picture the offending CorBon bullet. The CorBon bullet has a much different profile than does the 124gr hardball, doesn't it? THAT is your problem - the CorBon (and some other newer HP designs) simply use a bullet shape and cartridge OAL that in sum is so far removed from the 'traditional' hardball specs that, if you wind up on the short end of normal production tolerances, your freebore dimension will be too short. The result is that your pistol will start to engrave the rifling on the slug as the round is chambered.

There are three solutions to this; live with it and continue to use CorBon, don't use CorBon anymore and use a round that works mo' better in your CZ, or avail yourself of CZ's excellent customer service and let them increase the freebore slightly.

By the way - this is incorrect terminology:

Looks like I may have to ship the gun (Or possibly just the barrel?) to have it reamed, or perhaps they could just send a replacement barrel that's reamed with a slightly longer chamber. The additional length that's required is probably between 1/32nd and 1/64th inch. It's not much. The CHAMBER is not too short - the freebore is. If the CHAMBER was too short, you'd not be able to seat a round and place the pistol into battery. The chamber is the part of the barrel that encases the brass cartidge, and is dimensionally quite standardized.

freewheeling
April 4, 2004, 04:37 PM
rbernie:

The CorBon bullet has a much different profile than does the 124gr hardball, doesn't it? THAT is your problem - the CorBon (and some other newer HP designs) simply use a bullet shape and cartridge OAL that in sum is so far removed from the 'traditional' hardball specs that, if you wind up on the short end of normal production tolerances, your freebore dimension will be too short. The result is that your pistol will start to engrave the rifling on the slug as the round is chambered.

Yes, I know the geometry of the bullet is the problem. I had that sussed out the minute I removed the barrel and dropped a few different rounds into the "chamber" (freebore?). I gather that the Corbon would probably work anyway, it'd just be way inconvenient to "unchamber" or extract a round. There'd also be a tendancy to compress the length if the same round were it chambered repeatedly is this condition, though I don't know what impact that would have on performance. The round that I pulled out with pliers fired just fine in the Kahr, so one chambering didn't change things significantly.

It would be nice to use the same defensive round for both guns, and to be certain that all future ammo (such as frangible?) is compatible, but I really like the CZ, so I'm not complaining so much as wondering what the heck is going on. Thanks for the explanation.

cratz2
April 5, 2004, 02:59 AM
Back when I bought my first CZ (a standard blued CZ75B) I thought Triton and CorBon were the only ammo makers worth considering for self defense. While I mostly shot S&B and Winchester White Box through it (and another CZ and three EAAs among others), I ALWAYS checked 115 +P CorBons in all my 9mms. To this date, I don't think I've ever had a single failure of CorBon ammo not feeding, firing or extracting in any 9mm.

You might have said somewhere and I missed it but, if you take a brand new round that hasn't been inserted in the barrel and insert it until it 'sticks' then wiggle it around a bit then remove it, look on the case and on the bullet to see where the exposed metal is... That should tell you if it's catching on the case or the bullet itself.

For what it's worth, I've read that the Kahr was designed around the 115 +P CorBon round... And with all due respect to you, CZ and Kahr, each gun should be tested with a desired carry load... There are all kinds of failure potentials. In my experience, loaded CorBons are shorter overall than most other 9mm HPs though they do have that very characteristic slant to the bullet. I'd either just not worry about it and use a different carry/SD ammo or have it reamed and polished... Shouldn't cost too much.

Good luck and keep us posted.

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