Author Topic: 125 gr SWC not plunking  (Read 2449 times)

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Offline nettle

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Re: 125 gr SWC not plunking
« Reply #15 on: May 19, 2018, 10:11:36 PM »
That makes sense. I will leave a small amount of shoulder sticking out of the case mouth.

Offline armoredman

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Re: 125 gr SWC not plunking
« Reply #16 on: May 19, 2018, 10:24:42 PM »
The lowest I ever went was 1.020 with Berry's Target Hollow Point - those things are a PAIN...but accurate.
Good luck, and BTW, this is why I had to quit casting the Lee 125 round nose for my CZ, as the meplat would foul. The 124 Lee works like a charm, and they all love them.
Powder coated? That's fun to do, too.

Offline Wobbly

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Re: 125 gr SWC not plunking
« Reply #17 on: May 20, 2018, 10:27:57 PM »
Taper crimp is checking .380" +.000"/-.003".


That's an issue right there, my friend ! You can't be anywhere near 0.379 or 0.380". You need to read the article on taper crimp in the Stickie portion of this forum.

 ;)
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Offline nettle

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Re: 125 gr SWC not plunking
« Reply #18 on: May 20, 2018, 10:41:39 PM »
OK. I just got the calipers out and did some serious checking. They are not checking .380" +.000"/-.003" but rather .375" +.001"/-.000". Lyrman's 49th says .380" so what am I doing wrong here?

Offline 1SOW

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Re: 125 gr SWC not plunking
« Reply #19 on: May 21, 2018, 12:03:37 AM »
Just To show an excerpt from the Wobbly stickie:

Quote
Therefore the above observations spawn several thoughts.
• First, that a good and truly useful taper crimp diameter for any auto cartridge is going to be 0.002-0.003" less than the case mouth dimensions shown in the SAAMI drawings. That makes the useful taper crimp dimension for 9x19 Luger equal 0.380 minus 0.003, or in the range 0.376-0.378", with most people using 0.377-0.378". (Notice that these numbers also fit nicely with those from the "Optimal" section.)

• Secondly, taper crimp is a function of the barrel. This since correct taper crimp promotes good cartridge feeding, and feeding deals with the interface between the cartridge and barrel. Therefore, no matter what bullet style, weight, or diameter you might be loading, the taper crimp diameter will never change, unless you change your barrel.

You can also Google "SAAMI Pistol specifications"  and select 9mm Luger Pistol from the menu and it shows measurement diagrams. They depict how the 9mm "seats on the case mouth" with more measurements than you can believe.  and the 9mm Luger bbl seats are standardized to .380" - minus a few thousandths.

If your crimp diameter AT THE case mouth is too small the case won't seat and can bypass the seat and jam into the bbl.  If your taper crimp is to large of a diameter,  the cartridge may not feed all the way in to the seat.

So, something in the range wobbly suggested will give you a reliable taper crimp. 
     

Offline M1A4ME

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Re: 125 gr SWC not plunking
« Reply #20 on: May 21, 2018, 04:30:43 AM »
Even when/if you get it to "plunk" in your pistol barrel you need to check it in your other pistol barrels just to be sure.

I loaded up some 125 grain LSWC for my 9MM CZ.  I had my CZ 75 Compact on me, I removed the barrel, played with the seating/crimp die till I got the bullets seated/crimped just right and put the pistol back together and loaded it before finishing my test box.

The next time I went to the range I took my compact and my P09.   I shot a few in my CZ75 compact and then picked up the P09.  The first round hung in the chamber of the P09 and I had to take the pistol home with that stuck round in the chamber (slide not fully forward) to pop it out of there.  I now carry a steel pistol cleaning rod in my range bag in case that happens again.

Even CZ's are not created equal. Small differences can still "make a difference."

Good luck with it.  I gave up on the particular LSWC used in this test and bought a different brand/style for the next test.  Just need to work my way around to loading some to see how they do.
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Offline IDescribe

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Re: 125 gr SWC not plunking
« Reply #21 on: May 21, 2018, 06:18:30 AM »
Okay, if crimp is so narrow that the case mouth can slip past the headspacing step in the chamber, it won't slip forward into the barrel.  It will just end up headspacing on the extractor.  Since 9mm cases shrink with reloading and seldom meet the. 754 spec, I suspect a lot of cartridges do that regardless of crimp.

I would suggest that one mistake made was your reporting crimp as 380  +.000/-.003.  You should have simply said .377-.380.   I had to read it a couple of times before I realized you weren't saying +/- .003, which would be a major problem.

SAAMI specs have a headspacing step that calls for a case mouth diameter up to .380.  Anything over .380 is a problem. I used to use .379 for bullets of .357 diameter, .378 for .356, and .377 for .355.  But that's when I cared to mess with it. Currently, I have had my taper crimp set for .379 for quite some time and don't change it.

.375 is too narrow.
« Last Edit: May 21, 2018, 06:00:18 PM by IDescribe »

Offline 1SOW

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Re: 125 gr SWC not plunking
« Reply #22 on: May 21, 2018, 12:25:16 PM »
We are all throwing a LOT of info at you at one time,  but this isn't rocket science.
Like ID and wobbly said,  once you get a good taper crimp within the usable sizes that Plunk into the chamber,  you're  good to go.

If we had to "write" how to tie your shoes,  it would surprise you how much explanation would be required. O0

Offline IDescribe

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Re: 125 gr SWC not plunking
« Reply #23 on: May 21, 2018, 06:57:16 PM »
Was just looking at SAAMI chamber specs.  Inner diameter at chamber headspacing step is .381.

Online painter

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Re: 125 gr SWC not plunking
« Reply #24 on: May 21, 2018, 07:05:27 PM »
Was just looking at SAAMI chamber specs.  Inner diameter at chamber headspacing step is .381.
What is the tolerance on that number?
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Offline Wobbly

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Re: 125 gr SWC not plunking
« Reply #25 on: May 21, 2018, 07:36:21 PM »
Was just looking at SAAMI chamber specs.  Inner diameter at chamber headspacing step is 0.381".

► Right ! And that's why I interpret the SAAMI cartridge drawing number of 0.380" not as a number to be achieved, but rather as a absolute maximum dimension. One which you'll want to be smaller than, and 0.002 to 0.003" smaller provides all the clearance necessary to allow cartridges to fall into and then back out of the chamber at high speed.

► Taper crimp setup is a completely separate issue from jamming the bullet's shoulder into the rifling forward of the freebore. Once you eliminate the concern of taper crimp NOT being your issue, then you can get back to the OAL concern.

That's simple enough with 0.355" dia jacketed or plated bullets. But with lead you have the added concern of the oversize bullet seeing some resistance as it slides into the freebore. You don't want to confuse freebore tight fit (a given with lead bullets) with jamming into the rifling (a problem to be avoided). So maybe sanding 0.001 or 0.002" off the bullet before seating would help you there.


9x19mm Luger is a small cartridge, but one should never confuse "small" with "easy".

 ;)
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Offline IDescribe

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Re: 125 gr SWC not plunking
« Reply #26 on: May 22, 2018, 06:52:30 AM »
My non-scientific path to determining crimp:

I did quite a bit of reading on loading for 50 yard bullseye, where they test and tinker with every little variable to determine the ideal, and I found by far the most common crimp for 9mm pet loads among bullseye shooters with .355 jacketed bullets to be .377.  So I adopted that on faith that bullseye guys were the ones who had sorted all that out for me. And for every thousandth up from that in bullet diameter, I opened up the crimp a thousandth.

Then I eventually, after loading some .357 bullets with a crimp of .379, decided to leave that alone, regardless of bullet size, to see what would happen.  And nothing happened.  I could detect no differences in performance with .355 or .356 bullets of any type at the larger crimp, and I've just left it alone since.

My sample size of 9mm pistols is four-- 2 CZ, 1 Glock, and 1 HK, so take that into consideration, but I have no problems with my ammo in any of my pistols.  And the only failures to feed I can recall in any of these pistols with my ammo have been the result of exceedingly gummed up extractors where extractor movement was restricted, or high primers, which also restricts extractor movement. A crimp of .379 has functioned perfectly for me, and awfully convenient to be able to just leave alone.

Offline IDescribe

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Re: 125 gr SWC not plunking
« Reply #27 on: May 22, 2018, 01:14:26 PM »
So maybe sanding 0.001 or 0.002" off the bullet before seating would help you there.

I'm going to assume that was a joke.  ;)

Anyway... I have no problems myself with oversized lead and plunk testing.  Have always been able to find a usable OAL.  Whether or not early contact with the walls of the freebore has ever led me to load shorter than necessary is a different matter.  I can't say with certainty.

What I have  had happen, though, is that I once accidentally shot coated lead loads for my VP9 through my ShadowLine, which plunks more or less all bullets about .03 shorter than my VP9, so those VP9 loads were definitely into the ShadowLine's rifling, and they were super accurate.  At the time, I recalled noylj having said he loads lead right into the lands, and since then I have often done the same for the CZ with good results.  Maybe I'm not into the lands at all, but into a  freebore squeeze.   I'll spend some time figuring out how to test that. My assumption has been that loading lead into the lands has had the effect of "trueing" the bullet to the bore.

And to that end, I once read an article where a guy tested 9mm for accuracy, grouped by different case lengths.  The shorter the cases got, the worse precision got.  His assumption was that it was about headspacing on the chamber step VS the extractor, where headspacing on the chamber step squares the case to the bore and aligns the bullet axis with the bore axis.  But if the case was short enough to head space on the extractor, that you lost the squaring effect of the chamber step, and the cartridge would rest on the case mouth in the chamber, not perfectly aligned. In his tests,  case lengths of .750 - .754 were about the same in terms of precision, but below .750, things got progressively worse as cases got shorter, suggesting that cases were starting to hang/headspace on the extractor shorter than .750.

So while I personally think .004 shorter than SAAMI spec before extractor headspacing is a lot to ask in terms of tolerances, especially given that most 9mm cases don't even make it to .750, so I don't know that shorter than .749 is where the case starts headspacing on the extractor, but I'd say it's inarguable that there is some  case length below which that happens. And I know that precision rifle shooters will take stock Remington 700 actions and have the chambers and barrels "trued" to achieve that perfect pre-ignition alignment, so I suspect there is some truth to that writer's hypothesis in principle, at least, even if his specifics are a bit off.

Food for thought. :)
« Last Edit: May 22, 2018, 01:17:51 PM by IDescribe »

Offline 1SOW

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Re: 125 gr SWC not plunking
« Reply #28 on: May 22, 2018, 09:52:54 PM »
Interesting theory.  There must be a way to test that hypothesis.
Would seating "known" length cases provide evidence:
Could  a ..355 case that  "seats" be measured from breach face to the cartridge base?
  Then do the same with a .353" case that seats  and measure 2/1000" less distance to the breach face.
 At some point/case length,  the decrease in distance should stop decreasing.
Would that indicate resting on the extractor ...in that pistol?
Now how do you measure them? :-\

We're drifting off the OP's thread.

Offline JRR

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Re: 125 gr SWC not plunking
« Reply #29 on: May 24, 2018, 01:22:09 AM »
The one item not discussed is whether the bullet was sized before or after coating.  If it was sized before, the thickness of the coating may vary over the surface of the bullet.  This may explain why only a few would not chamber.  I load the NOE 128gr SWC sized at .358" and seated to 1.050".  No problems chambering in two different CZ barrels.  My bullets are made both naked and coated.  If coated, they are sized after.