9mm plunk test fail?

[Bird]

I have a new cz75bd, and trying to sort ammo for it.
I am using cast bullets sized to .357. The oal after bullet is seated is 1.095, and chambered round is not contacting the lands, with a max length of 1.105 touching the lands, so all seems well there.
When I plunk test the round, it sometimes sits a few thou proud, but with a little gentle push seats easily. When I invert the barrel sometimes the round will not fall out, and I have to use my thumbnail to extract it. I can not spin the case in the chamber with my fingers, but with very light assistance with pliers i can spin the case.
What I see is the throat diameter is a little too tight for the bullet. After the spinning of the cartridge, the bullet is making contact with throat for about 0.030''of its length, and now measures 0.356 to 0.3565'' in that area.
My question is, will that cause lead scraping/fouling, and eventual fail to chamber?
I guess I need to try it and see, but does anyone have experience with this?

[whisler]

My CZ75 had a very short leade in the throat (most do) so I sent it to Dougguy on this form for throating and now it takes what I want to feed it.

[Bigslug]

What's the diameter of the case mouth of your loaded round. Spec is .380". Possibly a classic case of needed a little more squeeze from your taper crimp die.

[armoredman]

CZs are notorious for short chambers. What boolit are you using? I have been using the 124gr Lee Tumble Lube for decades, sized to .356 loaded to the same as you, 1.095 with good effect.

[Bird]

Case mouth dia is.380'' to .3805''. The case fits the chamber, but an inked bullet shows a tight fit in the throat. Too tight by 1/2 to 1 thou.

[Bigslug]

What's your bullet design? I.O.W., will seating slightly deeper help?

[la5676]

CZs are notorious for short chambers. What boolit are you using? I have been using the 124gr Lee Tumble Lube for decades, sized to .356 loaded to the same as you, 1.095 with good effect.

As are many Glocks I have found.

[Bird]

What's your bullet design? I.O.W., will seating slightly deeper help?

No, its not a seating depth problem it a bullet dia/ throat diameter problem.....if it is even a problem. If I sized the bullets to .356, I would have clearance in the throat.

[justindad]

If you have tight chambering when the barrel is clean, you might be a failure to reach battery after a few hundreds rounds with all the boolit lube and powder soot. I have a pistol like this.

[Bird]

If you have tight chambering when the barrel is clean, you might be a failure to reach battery after a few hundreds rounds with all the boolit lube and powder soot. I have a pistol like this.

That was my thinking and concern.
I think I will go ahead and try it as is. I don't mind cleaning after a couple of hundred rounds.

[Dave W.]

It seems like the chambers on modern weapons are sized for jacket bullets, not cast. I have had to get most of mine reamed so lead bullets will chamber correctly.

[pcmacd]

I have a new cz75bd, and trying to sort ammo for it.
I am using cast bullets sized to .357. The oal after bullet is seated is 1.095, and chambered round is not contacting the lands, with a max length of 1.105 touching the lands, so all seems well there.
When I plunk test the round, it sometimes sits a few thou proud, but with a little gentle push seats easily. When I invert the barrel sometimes the round will not fall out, and I have to use my thumbnail to extract it. I can not spin the case in the chamber with my fingers, but with very light assistance with pliers i can spin the case.
What I see is the throat diameter is a little too tight for the bullet. After the spinning of the cartridge, the bullet is making contact with throat for about 0.030''of its length, and now measures 0.356 to 0.3565'' in that area.
My question is, will that cause lead scraping/fouling, and eventual fail to chamber?
I guess I need to try it and see, but does anyone have experience with this?

I see no problem here. Shoot away.

[Willie T]

Surprised nobody advised to drop the powder charge and seat deep enough to chamber freely and work back up, which is what I would do. Bird, you can seat all the way to just short of the ogive. Be aware that it will significantly change pressure. If you compare lead 9mm data sets, you will see instances of short OAL’s with a max charge weight equal to a starting charge weight with a long OAL and the same components. With suitable lube your bullet will size to the barrel and seal without leading. You can also try sizing to .356 for comparison. Ultimately you just need to work out the details for your pistol. Construct your ammo to fit your pistol. (You are already really close).
Willie

[gwpercle]

DougGuy can fix the problem with his magic ...
Open that tight throat up for you and presto ... no more problem .

If that isn't an option ... try a "truncated cone " boolit design like NOE's #358-124-TC
The front end of the truncated cone has been modified for tight throated barrels .
I bought the NOE mould and solved my plunking problems .
Gary

[Meatpuppet]

CZ's are notorious for short leades (throats). I think because the design was when a 115ge - 124gr FMJ was the cats meow. When CZ's became popular on the USPSA/IPSC competition, many people found the fatter ojive 147gr projectiles were having the same problems you have found.

I have 3 CZ SP-01, a CZ Phantom and CZ RAMI. All needed factory barrels to be kissed by a throating reamer (not chamber reamer) to allow for the fat ojive and normal seating depth. Loading short WILL solve the problem, but I am not a fan of heavy projectiles, fast powder and loading short. Pressure spikes are really easy to make by accident. The .356, .357, .358 sizes were not my problem.

If you are doing a single barrel, DougGuy is your answer.

[Randy Bohannon]

Another vote for it to go to DougGuy do his fine work, your barrel is cut for jacketed bullets . None of the current barrels are cut for lead bullets unless it’s specified with a custom order spec.

[megasupermagnum]

If what you say is true, just use a .356" sizer. Problem solved.

[DougGuy]

Have the barrel throated and move on with enjoying your pistol. Everything short of that is just another compromise.

[Iowa Fox]

Don't let case bulge above the extractor cut give you a sucker punch.

[aya]

As Iowa Fox said! Had the same problem, ca.10% of my reloads did fail the plunk test. Same bullet, same brass, same reloading procedure. Problem was a case bulge to close to the extractor groove to be reached by the sizing die. My brass is range pickups and have to be sorted prior to loading. I had already sized and expanded the brass, so i used my caliper! The square section above the jaws, the good ones fall through, but the bulged ones would not. Keep one of those to check that jaws dont move during check.

[gloob]

No, its not a seating depth problem it a bullet dia/ throat diameter problem.....if it is even a problem. If I sized the bullets to .356, I would have clearance in the throat.

This is why I use bullets sizers and/or taper crimp in some calibers and not others. My own 9's are loose enough to chamber my cast bullets as dropped, even though they measure 359 at some angles. My 45's and 40's need to be sized to fit in my guns.

And I additionally run my 40 ammo through a taper crimp die, after seating. If I don't taper crimp, the cartridges with thicker brass at the casemouth will stick in the chamber and leave fouling in the barrel of my Glock. If I taper crimp, they won't stick in the chamber, but they still foul. So if the taper crimp die does more than just lightly touch the case mouth, and I feel it do an actual crimp? That round goes into a separate batch, not to be shot through my Glock. My PMC cases are the thickest ones at the mouth, followed by Fiocchi. Most my other brass is ok.

Anyone know a practical way to easily/quickly turn down pistol brass?