Short COL can cause misfire?

[gifbohane]

This was the second visit to the range that I had this happen, 5 FTF out of 100.

This time I had the same problem with 5 FTF out of 100. I reloaded and fired the first two successfully. I kept intact 3 of the 5 FTF rounds. The other three rounds were the same COL both before and after the attempted firing. ……. at 1.120

 

[mrawesome22-250]

Primers weren't seated properly.

 

[higgite]

Primers weren't seated properly.

This ^^^, pure and simple. The light dimples in the misfired primers and then firing on restrike are dead giveaways. That would have been handy info up front.

 

[gifbohane]

Do you guys think that the crimp looks OK?

 

[higgite]

Do you guys think that the crimp looks OK?

Your pic is a little fuzzy, but the crimp looks okay to me. Have you measured the OD of the case mouth? Should be in the neighborhood of .380” +/- depending on case wall thickness. No less than .373”. You just want to take the flare out, not aggressively crimp. Even a tiny bit of flare is okay if it plunks good and feeds well, but ideal is no flare.

 

[mrawesome22-250]

Looks can be deceiving. Measure it and know for sure. Should be ~.380" O.D. at the case mouth.

Jinx

 

[jmorris]

With the barrel removed will the extractor hold the round against the breechface?

If so, that alone can set the primer off. I have found stuff at the range that couldn’t have possibly headspaced correctly but obviously fired.

Like a 9mm fired in a .40 S&W, for example.

 

[ATLDave]

I think two viable explanations have been identified in this thread: 1) primers not properly seated; and 2) bullet loaded too long for profile, jamming in lands and preventing slide from fully closing.

I'd start by eliminating #2 as an explanation. Pull the barrel and plunk every round you've got made up of this. If they don't all plunk and spin freely, then you need to shorten the OAL. CZ's often have very short throats. This may help generate their good accuracy, but it does mean you can't feed them long ammo of certain nose profiles. I would first test and eliminate this explanation.

 

[fxvr5]

Based on some posts, it's not clear why rounds are not passing the plunk test. Therefore, if you find a round that does not pass the plunk test, or jams when firing the gun, you MUST determine why they fail.

First, save those rounds.

Second, there are instructions on how to diagnose the problem at the link below. Use a magic marker as described in the link to troubleshoot your problem.

https://www.shootingtimes.com/editorial/reloading-tips-the-plunk-test/99389

 

[gifbohane]

Dave and fxvr-

Every one of these rounds passed the plonk test before I ever brought them to the range. The three I kept to examine, and showed a picture of above, still pass the plonk test. The rounds did not "jam" but failed to fire which is why I asked the initial question about OAL. I thought that they might be too short but I am getting the idea that they might be a bit long for a CZ barrel.

Now the guys might be right that I overcrimped and the five FTF rounds (out of 100) jammed into the lands but they did plonk when I got home. I plan to take a picture of one of them in the barrel later today and measure the circumference to .380. There is a problem with CZ's with the roll pin getting compromised with dry firing but the firearm is 4 weeks old and I did not dry fire it.

I am sorry for beating this to death but I need help and do not want to give up on a firearm with a great reputation. Photo to follow.. And Thanks to all for the comments.

 

[Walkalong]

Measure them at the case mouth to see if you over crimped. Check your priming setup/method and be sure to get primers fully seated to the bottom of the primer pockets. Double check that they plunk.

 

[ATLDave]

Dave and fxvr-

Every one of these rounds passed the plonk test before I ever brought them to the range. The three I kept to examine, and showed a picture of above, still pass the plonk test. The rounds did not "jam" but failed to fire which is why I asked the initial question about OAL. I thought that they might be too short but I am getting the idea that they might be a bit long for a CZ barrel.

Looking at the smaller/attached picture in your earlier post, that hazy ring around the base of the bullet looks like a throat-jam artifact to me.

With a bullet that's right on the edge of jamming, it's easy to get a false negative with the plunk test. Drop it in with some force... see if it spins. See whether you can get it to jam/stick if you apply a little pressure to the back of the cartridge, then see if it spins and drops free. You want to test whether a cartridge pushed into the chamber with the force of a closing slide gets jammed.

 

[roval]

are you sure it was in full battery when the hammer went down? and as i asked before was it hard to rack out. in hornady reloading manual the coal for your bullet as tested is 1.10 and your load is listed but as w231 ( so you should have a lot room to play with). your crimp doesn't seem excessive and wouldn't have bitten into the jacket why not seat some of those bullets deeper and leave as is or crimp just a tad more and see if it happens again ( i may get flamed for this but what would be the difference from the actual reloading process) check out 3:49 of this video. the slide looks like it's almost in full battery but just a smidge out of battery. it happens several times.

 

[higgite]

.....check out 3:49 of this video. the slide looks like it's almost in full battery but just a smidge out of battery. it happens several times.

Perfectly illustrates the value of the plunk test in new-to-the-reloader pistols. “Normal” COLs don’t always work, especially in notoriously short throated chambers such as CZs.

 

[gifbohane]

I really thank you all for the input.

All the rounds measure .376 more or less at the case mouth. The base of the bullet where it enters the mouth is .355. They were all previously "belled" to .381 to .383. The bullets all chronoed at an average of 1145 at 15 feet for what it is worth.

Walkalong- You are correct I primed these cases a long time ago and probably did it very (too) delicately.

The Hornady manual I have shows on page 866 that Hornady used a COL of 1.100 for the 115 Grain bullet (35557) I am using. I used 1.120 or a tad less (1.119.)

One important question - If the primers were not fully seated into the pocket would not the firing pin engage the primer earlier and have fired it? All the rest of the batch that fired on the first try showed the primer to be flush with the case base before and after the firing. The primers were essentially flush (.0005) with the base of the case. In the future I will clean the pocket and seat them further in.

BTW a small ring shows on the top of the bullet (about 1/16 down) which is where the seating die pushed down on the bullet as it was seated. I am also going to stop seating and crimping the 9mm at the same time.

Will try some of the other suggestions tonight.

 

[roval]

Perfectly illustrates the value of the plunk test in new-to-the-reloader pistols. “Normal” COLs don’t always work, especially in notoriously short throated chambers such as CZs.

it plunked in just didnt fall out as easily and cartridge base was at the right level . spinning it around is new to me.

 

[ATLDave]

Contrary to internet lore, the name "plunk test" is not 100% self-explanatory!

 

[Blue68f100]

I really thank you all for the input.

All the rounds measure .376 more or less at the case mouth. The base of the bullet where it enters the mouth is .355. They were all previously "belled" to .381 to .383. The bullets all chronoed at an average of 1145 at 15 feet for what it is worth.

Walkalong- You are correct I primed these cases a long time ago and probably did it very (too) delicately.

The Hornady manual I have shows on page 866 that Hornady used a COL of 1.100 for the 115 Grain bullet (35557) I am using. I used 1.120 or a tad less (1.119.)

One important question - If the primers were not fully seated into the pocket would not the firing pin engage the primer earlier and have fired it? All the rest of the batch that fired on the first try showed the primer to be flush with the case base before and after the firing. The primers were essentially flush (.0005) with the base of the case. In the future I will clean the pocket and seat them further in.

BTW a small ring shows on the top of the bullet (about 1/16 down) which is where the seating die pushed down on the bullet as it was seated. I am also going to stop seating and crimping the 9mm at the same time.

Will try some of the other suggestions tonight.

The firing pin will finished seating the primer, depending on the distance and energy of the FP it may or may not set it off.

The proper seating depth is when they bottom out in the pocket and just a tad more to preload the anvil.

 

[Phlier]

All the rounds measure .376 more or less at the case mouth

That could well be the problem. You're 4 thou too narrow in case mouth diameter. If the case mouth is too narrow, the cartridge can go into the chamber too far. This can result in there being too much distance between the base of the primer and the maximum effective reach of the firing pin.

In order for the cartridge to be in the correct position in the chamber, the mouth of the case *must* engage (headspace) correctly. Look down the barrel from the breech end. Right at the end of the chamber, you'll see a ring that is of smaller diameter than the rest of the chamber. The cartridge mouth must stop at that ring. If you over crimp, it won't engage on that ring, and the cartridge will end up too far into the chamber.

It is possible that you're not reading your plunk test result correctly; it's possible that the case is going too far into the chamber, but it "feels" ok. You need to look at the base of the cartridge. I'll see if I can find a link to a post here where a guy shows what a properly passing plunk test looks like... to be continued.

Edit: Check out @Walkalong 's great plunk test tutorial thread.
IMO, you're going to find yourself in the situation shown in the left most example in the picture in the first post of that thread; your cartridges are going too far into the chamber.

Why do I think this?: Your case mouth diameter is too small, and you're getting light strikes (FTF) on your primers.

Also, keep in mind that your gun is going to chamber that round with a lot more force than you will when you're doing your plunk test. A round that seemingly passes your plunk test might very well *not* pass the test when it's chambered with the force of the gun's action.

As another member here has suggested a few times, you would be well ahead by putting a few in a magazine, and (safely) cycling a few rounds through your gun without firing them. If they feel "sticky" when you pull the slide back to eject a round, that's a sign of the round going too far into the chamber.

 

[fxvr5]

All the rounds measure .376 more or less at the case mouth.

That could well be the problem. You're 4 thou too narrow in case mouth diameter.

0.376" is fine. SAAMI specs are 0.373" to 0.380" for the case mouth.

SAAMI specs for the chamber ledge are 0.358" to 0.362". For the case to slip into the throat the case mouth would have to be smaller than those numbers.

 

[higgite]

Contrary to internet lore, the name "plunk test" is not 100% self-explanatory!

That's why you hope people are savvy enough to do a forum search rather than having to re-explain it infinitum.

 

[ATLDave]

That's why you hope people are savvy enough to do a forum search rather than having to re-explain it infinitum.

Eh, what else we gonna talk about here?

 

[higgite]

Eh, what else we gonna talk about here?

Cartridge headspace?

 

[Phlier]

0.376" is fine. SAAMI specs are 0.373" to 0.380" for the case mouth.

SAAMI specs for the chamber ledge are 0.358" to 0.362". For the case to slip into the throat the case mouth would have to be smaller than those numbers.

That's assuming that his gun is made to SAAMI specs, hence why it's a good idea to do not just the plunk test, but to also manually cycle a few rounds and see if they are ejecting smoothly.

 

[ATLDave]

That's assuming that his gun is made to SAAMI specs, hence why it's a good idea to do not just the plunk test, but to also manually cycle a few rounds and see if they are ejecting smoothly.

CZ's are known to have tight chambers and throats, not ones so big that in-spec cartridges will have the brass slide past the chamber into the throat. What you're suggesting isn't impossible, it's just not probable.

On the other hand, probably 50% of handloaders who get their first CZ have some kind of rifling/bullet ogive engagement issue. Either this or lousy primer seating are the more likely explanations.