Author Topic: CZ 97 Barrel "Protrusions"  (Read 930 times)

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Offline Gunzanamo

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CZ 97 Barrel "Protrusions"
« on: March 13, 2018, 01:00:34 AM »
Hi, I recently snagged a CZ 97. They seem to be made of unobtanium so I was happy to get ahold of one.

First time out with factory hard ball was no problem. Managed to put 8 shots into 1 7/8" with 2 flyers at 12 yards. Very pleased for first time out.

I want to keep my shooting costs down by reloading and I particularly want some semi wad cutters. The manual says they are verboten. I tried some hollow points with no problem.

I bought a Lee mold that turns out to be a single radius round nose of 228 grains supposedly. I had done a fair bit of reading so I knew the learning curve would be fairly steep with pistol ammo. After much fiddling around I got my first reloads to feed and fire with a few failures to go into battery, A light shove from my thumb seemed to take care of it but still not ideal.

I bought some 185 grain Hornady JSWC's to try out and the learning came quicker second time around. I found that they would fit fine in the case length gauge but not in the chamber. Adjusting the bullet length and taper crimping lightly mostly took a care of that.

I noticed that the round would hang up on the case mouth on those small squarish protrusions on the upper back of the barrel. The left side one in particular. So I swallowed hard and stoned the left hand one a bit to radius the sharp bevel. With dropping the slide on them they seemed to chamber fine.

At the range I had about 3 out of 10 that FTF. A light pull back on the slide allowed them to drop into place and releasing the slide chambered them.

Today I loaded some 200 grain LSWC's. They are a bit longer and also seem to chamber OK. Better than the 185's. The test is in the shooting of course.

So now I have to expose my ignorance. What are those small protrusions on the back of the barrel for? I don't see what purpose they serve. I would like to do a bit more radiusing of them to get more reliable feed from the 185's just to broaden my bullet options. But I don't want to do any more until I know what function they serve. Hate to wreck a new gun and all.

Any help would be appreciated.
Professing to be wise they became fools.

Offline SI VIS PACEM PARRABELLUM

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Re: CZ 97 Barrel "Protrusions"
« Reply #1 on: March 13, 2018, 07:06:54 AM »
Are you talking about the 2 protrusions on the upper rear of the chamber? If so Those are where the barrel locks up with the slide in back and I wouldn't stone those at all. If you are having issues with rounds chambering it's likely due to the bullet style your using and the fact that CZ barrels tend to be short throated. There are many threads on this forum dealing with the short chamber and "push test" for bullet seating depth.
I cast 200 gr lrn for my 97 BD and load 230 gr. jacketed ball as well and I also have no issues with any defensive type ammo. Never wasted any time with swc's as they can be an issue.
« Last Edit: March 13, 2018, 07:34:38 AM by SI VIS PACEM PARRABELLUM »

Offline Gunzanamo

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Re: CZ 97 Barrel "Protrusions"
« Reply #2 on: March 13, 2018, 10:27:49 AM »
Thanks for the reply, Pacem.
Yes, those protrusions above the chamber. Since they are already beveled on their lower sides I was simply rounding them very slightly rather than leaving a sharp edge on them. It seemed to work since the 185 grains went from 100% FTF to 30% FTF. I suspect that the longer 200 grains will be even better. It shouldn't affect lock up since those areas don't appear to bear against anything. I'm not shortening them or narrowing them.

Can you give me an explanation on how they accomplish locking up? I can't see what they do or really bear against. It is kind of dark and inaccessible in there.  I see nothing that they move into. The barrel tilts up and there is a ridge along the top side that would provide resistance to moving back under pressure. There is also the lug on the bottom of the barrel. But those protrusions are so small they don't look like they could contribute much. Maybe they provide some side to side resistance?


Here is a pic. Notice the protrusion on the left is slightly rounded on the chamber side.

To my unstudied eye they look like they could be removed entirely (not saying I was thinking of doing so) and still function.

Once it warms up and the icy winds stop blowing I'll try out the LSWC and see how they do.

Thanks for the input.
Gunzanamo
Professing to be wise they became fools.

Offline Gunzanamo

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Re: CZ 97 Barrel "Protrusions"
« Reply #3 on: May 22, 2018, 12:33:14 AM »
Indeed the manual specifically and categorically states not to shoot wad cutters. But I thought, well other about pistols so do why not my 97B?

Well, I did stone the underside of the protrusions. I went lightly and just radiused the sharp factory angles. Things improved considerably. I went from 100% FTF to about 20% FTF. Then I used an arkansas stone to polish without removing metal. Even better but not perfect.

Then I ordered a 4 cavity mold from Accurate Molds. It has two different bullet profiles in one mold- 185 grain and 200 grain. A thing of beauty. I dind't even want to pour lead into it at first. I ordered SWC that have a radius from cone to shoulder. Last week I fired 100 rounds with not a single FTF.

I also turned a new bullet seater for my Lee die so that the die seats on the shoulder and not on the bullet nose. The shoulder height is the important issue. So far so good.
Professing to be wise they became fools.

Offline Earl Keese

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Re: CZ 97 Barrel "Protrusions"
« Reply #4 on: May 22, 2018, 06:27:13 AM »
What year was your 97 manufactured? All I load for mine is Acme 185 & 200gr coated swc's. I've never once had a feed issue.

Offline Gunzanamo

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Re: CZ 97 Barrel "Protrusions"
« Reply #5 on: May 22, 2018, 08:13:28 AM »
2015. I know many people say they have no issues with SWCs but other do. Not sure why. The manual specifically says not to use them.
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Offline IDescribe

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Re: CZ 97 Barrel "Protrusions"
« Reply #6 on: May 22, 2018, 01:35:47 PM »
I'd shoot JHP for a while, then go back to SWC.  My 97 took quite a bit of break in time.  I shoot SWC mostly in it now, no problem.

And I had a bunch of SWC that I loaded early that had feeding problems that after a good break in period (1000 rounds, maybe) fed perfectly.  Stop stoning the new pistol.  Give it some time to break in.

Offline tdogg

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Re: CZ 97 Barrel "Protrusions"
« Reply #7 on: May 22, 2018, 02:13:42 PM »
We need more details and pictures but I think you need to read to adjust your OAL so that just enough shoulder is protruding over the case mouth to allow smooth feeding.  I like to be in the 0.030 to 0.040 inch protrusion over the case mouth on my SWC for my 97BD.

Read this:
http://www.czfirearms.us/index.php?topic=68170.msg469875#msg469875

Cheers,
Toby

Offline cdhbrad

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Re: CZ 97 Barrel "Protrusions"
« Reply #8 on: May 22, 2018, 03:52:01 PM »
All I load for mine is Acme 185 & 200gr coated swc's. I've never once had a feed issue.

Coated SWCs in those weights from various caster are all my 97B has been fed since it came back from CGW with an E package conversion.  Mine is a 2013 vintage and not issues at all with feeding the same SWC rounds I use in  all my 1911s in .45ACP.   

Offline Earl Keese

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Re: CZ 97 Barrel "Protrusions"
« Reply #9 on: May 22, 2018, 03:59:09 PM »
All I load for mine is Acme 185 & 200gr coated swc's. I've never once had a feed issue.

Coated SWCs in those weights from various caster are all my 97B has been fed since it came back from CGW with an E package conversion.  Mine is a 2013 vintage and not issues at all with feeding the same SWC rounds I use in  all my 1911s in .45ACP.
I think 2012 was when they changed the feed ramp.

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Offline cdhbrad

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Re: CZ 97 Barrel "Protrusions"
« Reply #10 on: May 22, 2018, 04:43:23 PM »
All I load for mine is Acme 185 & 200gr coated swc's. I've never once had a feed issue.

Coated SWCs in those weights from various caster are all my 97B has been fed since it came back from CGW with an E package conversion.  Mine is a 2013 vintage and not issues at all with feeding the same SWC rounds I use in  all my 1911s in .45ACP.
I think 2012 was when they changed the feed ramp.


I think you are correct so I was surprised to see he was having issued with a 2015 gun. 


[Mods corrected the quote]
« Last Edit: May 23, 2018, 01:52:50 PM by Wobbly »

Offline IDescribe

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Re: CZ 97 Barrel "Protrusions"
« Reply #11 on: May 22, 2018, 05:21:49 PM »
My 97 would take SWC with a shoulder height in a super narrow window to avoid feeding problems when it was new.  This doesn't surprise me. 
« Last Edit: May 22, 2018, 06:34:58 PM by IDescribe »

Offline Gunzanamo

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Re: CZ 97 Barrel "Protrusions"
« Reply #12 on: May 22, 2018, 06:31:49 PM »
Thanks for all the replies.
1. I, too found that shoulder height is critical. That is why I made the new depth plug so that it registers on the shoulder and not on the nose.
2. I, too found that the chamber is tight for length. Rounds that will be "go" in the cartridge gauge will often be a "no go" in the chamber. So I take the barrel off and use that as my depth gauge. Works every time.

3. I also found that the chamber diameter is looser than the gauge. Use the barrel.

4. I found that the shoulder form of the SWC makes a big difference. A radius is much superior to a flat shoulder.

5. Radiusing the "protrusions" was the single biggest improvement to getting the wad cutters to feed. I went from 100% FTF to 25% FTF and then with the radiused bullet shoulders it went to 0% FTF. 

6. So I still maintain that the stoning job is a big improvement. It isn't much material removed. Just enough to remove the sharp edge that the cartridge CASE- not the bullet shoulder caught on.

When I have a moment I'll try to get some pictures on.
Professing to be wise they became fools.

Offline SI VIS PACEM PARRABELLUM

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Re: CZ 97 Barrel "Protrusions"
« Reply #13 on: May 22, 2018, 06:58:26 PM »
The problem is the "stoning" job you did likely just sped up what would have worked out just fine after a break in period and down the road could cause a tolerance issue. Time and rounds will bear that out.

Offline IDescribe

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Re: CZ 97 Barrel "Protrusions"
« Reply #14 on: May 22, 2018, 09:30:09 PM »
The problem is the "stoning" job you did likely just sped up what would have worked out just fine after a break in period and down the road could cause a tolerance issue. Time and rounds will bear that out.

Correct.

Gunzanamo,

I believe 500 rounds is a commonly made break-in recommendation.  In my case, those SWC rounds that wouldn't feed reliably in my first outing with my 97 fed fine much later on, I'd guess around 1000 rounds, but I don't actually know when they would have started working because I wasn't trying them out along the way.  They didn't work, then they did.  Not sure at what stage of break in they became good to go.

At the end of the day, you don't know why your rounds are starting to function better, but one guarantee I can make you is that there's more break-in occurring in the first hundred rounds than in the second hundred, or fifth hundred, or whatever.  You were changing bullets and OALs and stoning metal off the barrel hood.  But along the way, every time you disassembled the pistol, fired the pistol, cycled the slide manually, you were breaking it in.

You have loads that are functioning, and that's good, but the idea that stoning was the solution, or partial solution, is a guess, and given that the rest of us feed SWC rounds without stoning metal off the barrel hood, it's probably a bad guess.

I can also tell you now that if the case mouth was catching the barrel hood, the bullet was seated to deep, probably flush with the case mouth.  I've done it. If the shoulder is above the casemouth, the case mouth can't hit the barrel hood.  The bullet shoulder hits it instead and prevents it.

Your problem was most likely incorrectly (for that gun) loaded ammo and a stiff, gritty new gun. 

« Last Edit: May 22, 2018, 09:32:18 PM by IDescribe »