125 gr SWC not plunking

[nettle]

I'm getting some failures to return to battery with coated 125 gr SWC. These seated at 1.080" COL and a crimp diameter of .380". Some of these rounds are not plunking in the barrel (3-4 out of each 100) and when they do the coating is getting scraped off the bullet shoulder that sticks out of the case mouth. I have read of short chambers on CZ's (this is my first CZ) and my guess is just to start shortening the COL until these rounds plunk consistently. Any advice ore suggestions would be greatly appreciated.

[1SOW]

If you say the "specific bullet company",  others here may have experience with that particular bullet.
Generally,  shortening the oal at some point should fix the Plunk test results,  but oals below 1" aren't ever recommended for CZ 9mm pistols.

[nettle]

At 1" the shoulder of the bullet would be flush with the case mouth which to me would seem to fix the problem.

A friend casts and coats these for me. I have shot about 20K of his SWC bullets in 45acp. I doubt it is the bullet's fault.

[m1a_scoutguy]

What are they sized at ? Check the brass on ones that are giving you a hard time. Certain type's/brands of brass are just not good for reloading and can be problematic. CBC/Americ and some others. Plunk test is a viable test for OAL & correct crimp but get a Wilson case gauge and check them with that before pulling the BBL and testing, it will save ya some aggravation for sure .

[nettle]

Sized to .357". What would the Wilson gauge tell me that the barrel isn't?

[snakeye]

Have you tried measuring the diameter on the ones that passed the plunk test against the ones that didn't pass...measured at the point where the coating scraped off?

[m1a_scoutguy]

Nothing really "but" once you get the OAL figured out you can use the case gauge to check without taking your gun apart. Its a minor convenience really. Say your gonna run a Match or just shooting with buddy's and ya want to make sure everything is GTG,etc. Say your gun is dirty and ya don't feel like cleaning it (Uh that's ME,,LOL) ya can just use the gauge to check stuff. Just my 2cents worth I guess, heck there only around $20 bucks or so, well worth it I feel. I will also say I have a buddy that casts bullets and we Powder Coat them and then size them to .356. It was before I had CZs but we use to size them to .357 and we would have an occasional one that would not "plunk" or go all the way in the case gage & the majority  of the ones that did NOT work were CBC brass and some others that were pretty crappy. Since we have been going with .356 the issue has gone away even with the CBC and other junk brass ! What gun is it if ya don't mind me asking, I know my P-07 seems to have the shortest lead/chamber so if my rds run in that they will run in any CZ I have. Something to think about I guess.

[nettle]

I have rechecked everything and dimensionaly everything seems to be OK. I do these spot checks while reloading anyway so I didn't expect to find anything wrong. I am new to reloading 9mm but not new to reloading. I have been reloading for decades.

I do have mixed range brass but am not seeing any out of tolerance crimp diameters. Really everything seems to be correct except the fact that I may have to shorten the COL more than I would prefer to.

[1SOW]

9mm and 45 Cal can't be compared ,  especially in a CZ.  9mm is different animal all together.
With a home made bullet we can only guess at the cause.

[m1a_scoutguy]

I have rechecked everything and dimensionaly everything seems to be OK. I do these spot checks while reloading anyway so I didn't expect to find anything wrong. I am new to reloading 9mm but not new to reloading. I have been reloading for decades.

I do have mixed range brass but am not seeing any out of tolerance crimp diameters. Really everything seems to be correct except the fact that I may have to shorten the COL more than I would prefer to.

I say go down to .356 and the majority if not all your problems will go away. You shouldn't have to shorten your OAL that much !  Its the bullet bulging the case I say,and I say check the Head stamp on the problematic rds,it could be any make but the ones mentioned are MORE problematic with .357 bullets. Will it make that much difference in the accuracy dept. for you , have you slugged your BBL,do you really need .357s are you shooting bullseye,etc ? If its just range/blasting ammo give it a try at least.

[tdogg]

Nettle,

How much of the shoulder is protruding over the case mouth at your OAL of 1.080 inch?  I haven't reloaded SWC for 9mm but in my 45 they like to have about 0.030 to 0.040 inch of protrusion over the case mouth for reliable feeding.  I'm not sure if this translates to 9mm or not?  I think your right that they all must plunk proper.  Have you determined what the maximum OAL with this bullet is (either with the push test or iterative seat/plunk test)?  You may be right on the edge of the bullet max OAL and your process variability is causing some to be too long for your barrel.  Usually you find the max OAL and subtract 0.015 (or whatever gets you about that much to a nice number for an OAL) to account for any future process variability.

What seating stem are you using to seat these?  Any chance the cartridges that cause the failure to return to battery have a crooked bullet?  I used to have a flat seating stem for seating SWC but now have a modified stem that seats off the shoulder.  I think they seat straighter now than before, but its hard to quantify/prove it.

What type of crimp die are you using?  Assuming your running a taper crimp and given your running 0.357 bullets you are in the ballpark with 0.380 but you may try dropping it to 0.378.  Just pulldown a finished cartridge and verify you don't see any marks at the case mouth with the increased crimp.

Hope this helps, post up your max OAL with that bullet in your barrel.  A picture of the bullet and finished cartridge would be helpful as well.

PS, I wouldn't worry about shooting coated lead 0.357 bullets.  That is all I shoot out of my 9mm CZ's. 

Cheers,
Toby

[Wobbly]

3 problems can show up with these signs...

? Taper Crimp
The chamber on a 9x19mm Luger is tapered. Incorrect taper crimp on a cartridge will jam into the chamber and keep the slide from going into battery. Read the "Stickie" on Taper Crimp at the top of the forum and make sure your ammo complies. Click Here

? Cases used in 9 Major
Sometimes range pickup brass will have been fired in a "9 Major" gun and due to the VERY high chamber pressures, the brass will be expanded beyond all usefulness, This expansion will be found at the base of the case where the Sizing Die can't possibly reach. A good cartridge gauge will find these. Read this.... http://www.czfirearms.us/index.php?topic=97209.0

? Wrong OAL
Tdogg is correct. It's not the OAL that gets you into trouble, but where the shoulder of the bullet lands relative to the rifling. Any bullet shape that brings the full 0.355" diameter forward of the case mouth is problematic when used in the 9mm CZ chambers. The left hand example in the following cartoon shows how you can get into trouble....



As reloaders we work and converse in terms of "OAL", but where the meplat of the bullet falls is of ZERO consequence ! What you need to control with a SWC is how far the bullet's shoulder protrudes into the chamber.

A simple push test (as we call it) will show you what your Max OAL with your bullet in your barrel is. It is not as effective with lead bullets, but with patience it can be done. Click Here and follow the instructions.


This last one is probably your prime suspect, but you really need to check all 3.

Hope this helps. 

[Wobbly]

Further....
Because the shoulder location is SO important, you need to use a seating anvil that pushes solely on the shoulder, and NOT the meplat when seating SWC bullets. Most reloaders are tempted to use a flat anvil and simply push on the bullet's flat nose, but that does not precisely control where the shoulder ends up.

This is probably adding to why some of your cartridges are OK, and some are not.




Just so you don't get depressed or upset allow me to add... it really doesn't matter how long or how much you've reloaded in the past. Reloading for the 9x19 cartridge in the CZ chamber will teach you more about reloading in a week than you learned in the last 10 years with other cartridges and guns. In the end, you can take all that new knowledge you're about to acquire back to your other cartridges and improve them. So it's worth the learning curve.

Welcome to the forum !   

[nettle]

Wobbly and tdogg. You saved me hours of research with your reply's. Both of you gave my an excellent beginner's tutorial on reloading 9mm SWC.

I am using a Dillon 550 with Dillon dies. I have the stem in the seating die turned so that the shoulder on the bullet is being pushed on while seating. Taper crimp is checking .380" +.000"/-.003".

If I seat the SWC bullet shoulder flush with the case mouth the COAL will be about 1.000". I haven't tried this new seating depth yet because I haven't any time to sit down at my reloading bench. When I do though (soon) I am going to load a few at the 1.000" COAL and give them a try.

When I first got the gun I wasn't having any feeding issues and still had some reloads left that I was using when I first started loading. These are checking about .030" shorter on the COAL than the ones I am having problems with now. I think shortening my COAL will fix the problem.

[IDescribe]

You don't want the bullet shoulder absolutely flush with the case mouth.  You want it a hair above.  If it's flush, the sharp edge of the mouth can catch and cause feeding problems.  You want just a hint of soft rounded shoulder hitting the feed ramp.