Failure to feed when loading mag

[IDescribe]

OP, how did you arrive at your chosen OAL?

[MarilynMonbro]

OP, how did you arrive at your chosen OAL?

Plunk test  It was set a little longer, maybe 1.120-1.125 but I shortened it to 1.110 when this issue crept up about 1,500 rounds ago thinking the oal was too long

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[IDescribe]

What was the actual max - - the length at which it touched the rifling.

[MarilynMonbro]

What was the actual max - - the length at which it touched the rifling.

That measurement is your exact chamber length for that bullet in that barrel.  I use mixed brass so I grabbed 4 random cases for this test
1.1425
1.1465
1.1410
1.1490

subtract at least 0.015" from that number to obtain your Maximum Usable OAL.

1.1275
1.1315
1.125
1.134

Edit - I should have noted my OAL will probably go back to what it was before if I determine this is not a OAL issue. It's looking like a crimp issue

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[IDescribe]

What was the actual max - - the length at which it touched the rifling.

That measurement is your exact chamber length for that bullet in that barrel.  I use mixed brass so I grabbed 4 random cases for this test
1.1425
1.1465
1.1410
1.1490

subtract at least 0.015" from that number to obtain your Maximum Usable OAL.

A .015 cushion to allow for variation and ensure you stay out of the lands is a good rule of thumb for new reloaders, or old reloaders who are not accustomed to dealing with OAL.

Once you know how tight your gear and your arm will keep OAL, you can lower that a bit.  I start with .010 by default, and I can cut that to .005 if I like, no worries.

Remember that OAL is from the base of the case to the nose, but the nose never touches anything directly.  It's the point on the ogive just above the shoulder that makes first contact with the rifling that we are worried about.  And that is far more consistent from bullet to bullet than the nose.  Those numbers you provided above have an extreme spread of .008.  I guarantee the spread wouldn't be that big if you could measure precisely to the point on the ogive that makes contact.  The reality is that your bullets are going to be a hair different in length at the tippy tip.  Takes only a small lump in the coating to add a thousandth or two.

I would recommend you measure bullets outside the case, and conduct that same test with bullets that measure exactly the same length.

Also, load one to 1.160 in a dummy round.  Size the case, no primer no powder, flare, seat the bullet to 1.160, crimp to .378.  Then see if that cartridge will plunk and spin freely in the chamber.  If it does not, seat it two or three thousandths and try again, and again, and again until it spins freely while inserted all the way.  And when it spins freely, take that measurement.   

[MarilynMonbro]

1.160 or 1.260? You mean 1.260 because the .015 cushion puts me about there?

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[painter]

1.160 or 1.260? You mean 1.260 because the .015 cushion puts me about there?

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1.169 is maximum length for a 9mm cartridge.

He means 1.160.

[MarilynMonbro]

1.160 or 1.260? You mean 1.260 because the .015 cushion puts me about there?

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1.169 is maximum length for a 9mm cartridge.

He means 1.160.

Herp derp! You're right. I've been reading numbers too much today and read them wrong lol

1.160 didn't pass plunk test, going down to 1.135 seems to do it. This was with two bullets with the same length

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[IDescribe]

1.160 didn't pass plunk test, going down to 1.135 seems to do it. This was with two bullets with the same length

What I'm saying is to load a dummy round at 1.160, then keep seating the same bullet a little deeper, a little deeper, .002-.003 at a time, until it finally plunks and spins freely fully seated in the chamber.  That is another way to find max OAL for that bullet in that chamber.  THEN you can make loads starting .010 shorter than that.  Make 20 of them, then 20 .010 shorter still.  And make twenty rounds a piece shortening in .010 increments -- 1.140, 1.130, 1.120, 1.110, etc.  And make enough rounds at each increment that if that OAL is going to produce these failures, you've made enough rounds at that OAL that the failure will show up.  If that means more than 20, then load more than 20.   But this could help you find the OAL that flat our works.

Just guessing and trying this OAL one day and that other OAL the next time, THAT could lead to a long, frustrating process.  Better to make a bunch at once and solve the mystery in one day. 

[Wobbly]

What was the actual max - - the length at which it touched the rifling.

That measurement is your exact chamber length for that bullet in that barrel.  I use mixed brass so I grabbed 4 random cases for this test
1.1425
1.1465
1.1410
1.1490

Sorry, but I disagree. The instructions for the "Ammo Forum push test" state that it cannot be used as effectively with lead bullets. The reason for this is that lead bullets tend to be larger diameters, and those larger diameters will hang the bullet up on the barrel freebore.

It's right here...

There are several ways to do this, but here's my method.... Fit a new jacketed or plated bullet into a fired case. (No powder; fired primer.) If you try 2 or 3 bullet/case combinations you'll end up with 1 or 2 where the bullet is a snug "push fit". Fit the bullet inside the case, but leave the OAL out at an exaggerated length; any OAL longer than what you need.

Therefore, since you can't see inside the chamber, it's hard to distinguish what feature is doing the push-back.... the taper crimp, the bullet diameter, or bullet ogive contacting the lands.

As I said before, Lead is cheap, but Lead is not easy. When you go for the economics of Lead you automatically introduce 10 more "gotchas", which are NOT mentioned in the OAL article. I contend that if a lead bullet properly fits the CZ barrel, then it probably will not enter the CZ freebore easily. That's "easily" as in "the ability to get good, useable numbers using the Push Test".

The first step I would take is to reduce the diameter of your blue bullet in your test cartridge to a maximum of 0.355 to match the diameters of plated and jacketed bullets. When you get your test cartridge to a taper crimp of 0.376/0.377 (which you found yourself) and your test cartridge bullet to a diameter of 0.355, then I believe things will go much better for you.


Hope this helps. 

[Wobbly]

I tested 50 factory rounds and had no issues. I tested 30 reloads and 2 failed to go in. The crimp on those is 0.3785 and 0.3780

? And what was the taper crimp diameter on the factory rounds ?

? Any taper crimp measuring less than 0.380 should fall into the chamber and then back out. If that fails, then you may have additional issues...
? Your chamber may be under-sized, according to SAAMI standards
? Your caliper might need "zeroing" or replacing
? Your chamber may be fouled with lead or other obstructions

Dillon calculator says

Neck tension only_(.000)0.375
Very Light Crimp_(.001)0.374
Light Crimp_____(.002)0.373
Moderate Crimp__(.003)0.372
Heavy Crimp____(.004)0.371

And
Neck tension only_(.000)0.377
Very Light Crimp_(.001)0.376
Light Crimp_____(.002)0.375
Moderate Crimp__(.003)0.374
Heavy Crimp____(.004)0.373

What "Dillon calculator" is that ? I strongly disagree with those numbers when the ammo is used in a CZ pistol, for the reasons stated in my article on Taper Crimp.

I just sized a case and shoved a bullet in it. The "crimp" measures 0.3755

I've never done this test before. I saw it on the crimp thread.

This statement raises questions...
? What instrument did you use to measure taper crimp to 4 decimal places ?
? So have you changed your taper crimp setting yet to agree with the 0.356" ?


Inquiring minds want to know.

[MarilynMonbro]

Here's a link to the calculator I referenced https://dillonprecision.net/crimp-calculator/

My blue bullets bullets are .355.  I am using a Neiko branded digital caliper

I haven't changed the crimp setting yet. I'm running low so I'm waiting to order more before I start loading test bullets

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[Wobbly]

Here's a link to the calculator I referenced https://dillonprecision.net/crimp-calculator/

Notice they don't recommend using any of those TC diameters. That's simply a calculator.

My blue bullets bullets are 0.355"

Is that their nominal diameter in the catalog, or have you been measuring them ? To work correctly in a CZ they better be at least 0.356", and hopefully closer to 0.357". Maybe even 0.358". That's some of the previously mentioned "10 more gotchas" when you load with lead.

I am using a Neiko branded digital caliper.

That's the same caliper you can buy at Harbor Freight for ~$10. Got one just like it and they work pretty good for reloading. However, don't fool yourself. The caliper may display 4 decimal places, but that's a long way from actually measuring 4 decimal places.

I haven't changed the crimp setting yet. I'm running low so I'm waiting to order more before I start loading test bullets.

So what's keeping you from running the incorrectly crimped bullets back through the TC die and correcting the issue ?


And again, what was the crimp diameter on the factory rounds ?

 

[MarilynMonbro]

So what's keeping you from running the incorrectly crimped bullets back through the TC die and correcting the issue ?

Nothing - I just have two different people recommending different things so I haven't done anything... Yet [emoji4]

And again, what was the crimp diameter on the factory rounds ?

I'll get that info when I get home tonight. I don't remember

[Mods fixed quotes]

[MarilynMonbro]

Crimp on the factory rounds is .376 - .377

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