CZ P10C Blown Primer / enlarged case

[stever_reynolds]

So, I initially posted this on TheHighRoad, but was instructed by a member to post here since I was using a P10C and the discussion went in the direction of possible OOB primer strike, over-charged case, bullet set-back and lots of questions about OAL and CZs having shorter OAL tolerances than other guns.  I just started reloading.  This was my first batch of 100 rounds with the following configuration:
- Berry’s 115gr RN
- CFE Pistol (4.9gr)
- COL 1.150-1.157 (I am not sure why, but I had about a half dozen that were 1.16-1.168 that I reseated and recrimped until they were between 1.150-1.155)
- mixed brass
- CCI Small pistol primers
- Lee Loadmaster (5 station progressive press)

I shot about 25 rounds through a crono and was getting 995 ft/s avg speeds. SD was not great (20-30 between magazines), but I was really just looking to target practice, not try to produce match ammo, so I moved away from the crono and started shootings at a cardboard target.  About 10-15 rounds in I had one round really snap back on me and new something wasn’t right.  I checked to see if the round ejected and if the gun cycled and it did.  I shot another 10 rounds or so and everything functioned fine.  When I picked up the brass I found the below case with primer blown out and head case significantly expanded, but case was fully in tact (no rupturing).  I got responses on The HighRoad that it was over-charged case to out of battery ignition, to bullet back setting, etc.  lots of questions about my COAL being too long, however, all of the remaining rounds pass the plunk test on my CZ P10 barrel.  The other interesting thing is I followed the suggested steps to find max COAL by placing a bullet in a spent case, push it into my barrel until it is all the way seated and then carefully pull it out and measure.  I am getting 1.185 using two different cases and trying a Berry’s 124gr RN and 115gr RN and get the same with both.  This seems way too long, so I checked on my P10F barrel and get the same 1.185 measurement.  Unless the bullet is pulling out of the case when I slowly pull it from the barrel, this OAL seems really long, considering the recommendation is to then back of .0150, which would put the safe OAL at 1.170 (out of spec).  I am new to this forum and am seeing I need the app to post photos so I will update this with photos shortly.

[stever_reynolds]

Pictures of the case with blown primer

[SI VIS PACEM PARRABELLUM]

Your coal is way too long. saami max is 1.169 and I guarantee you even 1.150 is far too long for a CZ chamber. Something is going amiss during your "plunk" testing as there's just no way on this earth your coal is coming up correct. You can follow the stickies on this forum and find much great info on how to get to a safe coal for your pistol. Go to the directory section at the top of the page and scroll down to finding max oal for CZ/DW pistols. Everything you need to do it properly is there.
I own 5 CZ's at present and I have my coal set at 1.126 which allows safe chambering in all 5 guns with the components I'm currently using.

[stever_reynolds]

Only other thing I can think of is my calipers are off.  I have measured several factory rounds and all of my manual loads and they are all between 1.150-1.155 (manual loads) and as high as 1.1625 for some of the factory loads.  If they are off they are consistently off.

[stever_reynolds]

Your coal is way too long. saami max is 1.169 and I guarantee you even 1.150 is far too long for a CZ chamber. Something is going amiss during your "plunk" testing as there's just no way on this earth your coal is coming up correct. You can follow the stickies on this forum and find much great info on how to get to a safe coal for your pistol. Go to the directory section at the top of the page and scroll down to finding max oal for CZ/DW pistols. Everything you need to do it properly is there.
I own 5 CZ's at present and I have my coal set at 1.126 which allows safe chambering in all 5 guns with the components I'm currently using.

I just verified my calipers are on.  They are measuring case after case after case at .754-.755” and my bullet diameter (.356) is spot on as well.  What CZs do you have?  I have a CZ-75 SP01 that I haven’t checked splunk and the max COAL process on this site that I also followed.  I do t know how I could be messing up the plunk test.  Drop in, listen for “plunk”, make sure it is flush with back of barrel, test bullet spins with minimal resistance, test bullet drops out freely when barrel is tipped upside down.  I have done that on several bullets that measure 1.15-1.155 from my manual loads and tested a couple factory rounds that measure 1.16.


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[George16]

I think you’re experiencing bullet setback and/or overcharged. Have you verified your scale? Are you reloading with the ceiling fan on? A ceiling fan can skew scale readings.

Can you rack a round into the chamber, eject it and measure the OAL? Make sure you measure the OAL prior to chambering the round using the magazine (not dropping the round into the chamber directly).

SI VIS, CZ chambers are not all short. For comparison, these are the OAL my czechmate takes 1.153”, TSO-1.145” and shadow 2-1.150” using Berrys 124 Gr bullets. For Precision Delta JHP, it’s has to be shorter and for RMR 124 MW, it has to be significantly shorter because of the bullet’s blunt ogive. This the reason I have my czechmates barrels throated to accept up to 1.175” OAL for my 9major load.

[stever_reynolds]

Thanks, George!  I will test 5 or 6 rounds that are all over 1.15 and report back if the OAL changes.


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[SI VIS PACEM PARRABELLUM]

I think you’re experiencing bullet setback. Can you rack a round into the chamber, eject it and measure the OAL? Make sure you measure the OAL prior to chambering the round using the magazine (not dropping the round into the chamber directly).

SI VIS, CZ chambers are not all short. For comparison, these are the OAL my czechmate takes 1.153”, TSO-1.145” and shadow 2-1.150” using Berrys 124 Gr bullets. For Precision Delta JHP, it’s has to be shorter and for RMR 124 MW, it has to be significantly shorter because of the bullet’s blunt ogive. This the reason I have my czechmates barrels throated to accept up to 1.175” OAL for my 9major load.

Basic CZ handguns 75B, BD PCR's, 75b compacts, P-07/09 so on all tend to run short. I don't have any of what you listed above so I can't speak to those but the 5 I still have are short and 5 of those I sold off in the past few years all where short. That's the general nature of the beast.
I don't disagree though he could be experiencing setback in which case a complete evaluation of the entire loading process should be performed.

[painter]

Your coal is way too long. saami max is 1.169 and I guarantee you even 1.150 is far too long for a CZ chamber. Something is going amiss during your "plunk" testing as there's just no way on this earth your coal is coming up correct. You can follow the stickies on this forum and find much great info on how to get to a safe coal for your pistol. Go to the directory section at the top of the page and scroll down to finding max oal for CZ/DW pistols. Everything you need to do it properly is there.
I own 5 CZ's at present and I have my coal set at 1.126 which allows safe chambering in all 5 guns with the components I'm currently using.

I have to disagree about the OAL. A Berry's RN will load well over SAAMI max in a CZ chamber. The OP has a problem, but it's not his OAL.

[Togmaster]

I agree that 1.150 is not too long for a P10C barrel. I use 1.150 for my RMR 124 gn RN loads but I still think it is too long for 115 gn projectile. There isn't enough bullet in the case in my opinion with 115 gn projectiles. I think your problem, as mentioned above, is bullet set back probably caused by not seating deep enough.

[tdogg]

I'll ask the obvious,  are you sure that case is yours?  Anytime you are working up a new load you should be inspecting the cases as fired.   Not waiting till the end to pick them up with other range fodder.

You don't have to load the gun to check for bullet setback.   You can measure the cartridge and push the cartridge bullet first into your bench firmly and re-measure the cartridge.  If the length changes (shortens) you have a sizing/ setback issue.

New to loading on a progressive?  What scale?  What dies?  Did anything happen during that load development loading session that caused you to stop?  What is your process to handle stoppages?  Did you work up to this load? How did you arrive at this load?

Reloading safely requires having a reliable process with attention to detail mindset.   Starting out on a progressive wouldn't have been my first choice due to the steep learning curve and many moving parts of the progressive process.

Cheers,
Toby

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[Duke Nukem]

Pictures of the case with blown primer

What's going on with the rim of the case, it looks pretty dented.  Could the gun have caused that, or did that happen on the ground?

[Wobbly]

Lots of good info and ideas here. I knew Steve would be better off with more CZ minds on the subject.
My thoughts...

• The freebore on my P10c is shorter than that on my SP01. I have to be very careful when loading some bullets, like the RMR 124gr JHP.

• My experience with the Berry Mfg RN products is that they will typically "push test" to an OAL longer than the mag will allow. Out to 1.190" with some bullets in my SP01.

• While learning on a progressive is not optimal, Steve does seem to be on top of things and a knowledgeable student of guns and reloading.

• I'm with TDOGG... how can you be sure the brass was yours ?

• If we assume the brass was yours, it is very clear that specific piece did not fully seat into the chamber before being fired. If that is the situation, then 2 thoughts arise...
1. Where did your brass come from? It seems to be all matching Fed brass, but was it from you and your guns ?

2. I would check the gun. Gun cleared and safe. Allow the slide to move forward in increments as small as possible, and pull the trigger at each increment. Especially the last 0.20" before the slide goes into battery. The question we are trying to answer is, "Will the gun fire OOB ?" IOW, can the barrel be unlocked and the gun still fire ? If so the P10 needs to go back to CZ.


The root cause may never be known, but we can help refine your reloading process to eliminate issues on the bench.

[SoCal]

Was this used range brass...Could have been damaged and have nothing to do with your reload, maybe.

Is your Lee a AUTO progressive press, if not possible double charge, IMHO most likely.

How have you checked for bullet set back?

OAL is dependent on ogive and factory ammo is often close to 1.16, even 115 GR and usually works in CZ chamber.  Your Barrel has the final say, if finished rounds plunk and spin then you are OK. 

Variances in OAL are SOMETIMES due to how you work the press, as you get move time these usually get less and less frequent.

[stever_reynolds]

I'll ask the obvious,  are you sure that case is yours?  Anytime you are working up a new load you should be inspecting the cases as fired.   Not waiting till the end to pick them up with other range fodder.

You don't have to load the gun to check for bullet setback.   You can measure the cartridge and push the cartridge bullet first into your bench firmly and re-measure the cartridge.  If the length changes (shortens) you have a sizing/ setback issue.

New to loading on a progressive?  What scale?  What dies?  Did anything happen during that load development loading session that caused you to stop?  What is your process to handle stoppages?  Did you work up to this load? How did you arrive at this load?

Reloading safely requires having a reliable process with attention to detail mindset.   Starting out on a progressive wouldn't have been my first choice due to the steep learning curve and many moving parts of the progressive process.

Cheers,
Toby

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I’ll do my best to answer all of the questions:
- yes, the case is mine. I wasn’t at a range, I go out to a place out in the desert where very few people shoot.  It was a clear area and a sunny day.  I scanned the area for 5 minutes to make sure there was no brass there.  I picked up exactly what I shot (had all rounds in a Berry’s 100 round case) and even scanned the 12-15sq ft area another 15 minutes hoping to find one more round.  Where the case was at was on a very distinct wet patch that I walked past after pick up rounds from the previous 4 magazines, so I didn’t wait until the end to pick up my brass.  That is how I am quite certain it was mine.
- as far as bullet setback, I have bench pressed a dozen or more rounds and have also slammed forward another dozen or so of the remaining rounds from slide lock.  None of the rounds changed even 1/1000 of an inch after doing so.  I am somewhat sceptical about bullet setback unless there was something unique with the one case that I missed
- yes, new to reloading.  I have a Lee Loadmaster.  All Lee dies.  Station 1 universal recapping die, station two 9mm sizing / priming, station 3 expander / powder through die, station 4 bullet seating die, and station 5 Lee factory crimp die.
- yes, loading stopped about a half dozen times due to upside down case in the case feeding tube and a couple times where I started trying to watch too many things and getting moving too quickly and missed placing a bullet.  Protocol was to pull the indexing rod and pull the case that missed the bullet and let the other cases move through their stations and then reinsert the case with missed bullet back into station 4 after all the cases had moved through before adding more cases in the feed tube. 

Being my first time it is entirely possible I missed something or had a fluke with one case getting over charged.


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