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Plunk test failure rate.


calebj06

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So I plunk/spin tested around 300 rounds tonight. 

 

Had a total of 15 failures. 

 

Just St wondering how many failures some of you see when doing this test? 

 

I will also qualify it by saying that over half of these were loaded before I even knew what a plunk test was!!!   So obviously I'm new to pistol reloading. 

 

 

Caleb

 

 

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1 out of 300 is too many, but we need (much) more information.  What caliber/handgun, what bullets, OAL, press, dies.  What was your process for arriving at the particular die setup?  

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21 minutes ago, RickT said:

1 out of 300 is too many, but we need (much) more information.  What caliber/handgun, what bullets, OAL, press, dies.  What was your process for arriving at the particular die setup?  

 

9mm

glock 19

acme 124 coated and gateway bullet 115

1.075 on the acme 1.10 on the gateway 

Lyman tmag turret

hornady dies 

 

followed directions on crimp die. Was my first time ever doing one. 

 

Honestly the gateway I just went by the loading manual for 115gr bullet. Like I said, I knew nothing about a plunk test.

 

The acme  me I was learning to plunk test and also getting switched over from the 115's. 

 

Out of my 15  8 of them are 115 and 7 are the acme 124. 

 

I was also honestly say that I'm being picky. Some of them just barely failed the plunk test. Some maybe wouldn't spin. But there were 3-4 that were an obvious failure. 

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Just now, superdude said:

Where/how/why were they failing? Part of the plunk test is to determine the cause of failure. Did you do that?

Nope. Enlighten me. 

 

Im just assuming the OAL is a little long on them. 

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3 hours ago, calebj06 said:

  plunk  tested   300 rounds 

Had a total of 15 failures. 

 

I load 9mm on a SDB and frequently get at least 5 "failures" out of 300,

using JHP's - if I switch to lead bullets, the rate goes up    :(

 

Nothing wrong - I place them in my practice pile, and move on.

 

Most of the time, they chamber and fire perfectly.  But, why take a chance.

 

I don't even Plunk them unless its a large match - I get so Very Few fail

to ignite.   Before BE, I loaded 9mm for 30 years and had never heard of

The Plunk Test.   And, had Very Few no function perfectly., once I had

set the right crimp and the right OAL for that bullet in that gun.    :) 

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Some thoughts. 

 

The COAL / OAL published with reloading data for 9mm is typically significantly shorter than the SAAMI max.  SAAMI is what gun manufactures use to design barrels & magazines to function with commercial ammunition.  The shape of the bullet will determine the cartridge length.  A semi wad cutter is more likely to plunk test over a round nose at the same correct length.  

 

Rifle shooters typically make their cartridges as long as possible.  Pistol shooters shoot wad cutters that clearly have a 'jump' to the lands of the barrel.   Then there's the clear bullet jump from shooting of 38's in a 357 barrel for practice.  

 

So shorter than SAAMI seems to work.  Shorter than load data is never a good idea.   Somewhere in between ??? More than likely the " sweet spot " for your Barrel is in between the two extremes.  Finding it for each bullet manufacture takes time.  This is why some enjoy finding it and others always shoot the same bullets.

 

So if your bullets are the correct diameter back off the cartridge length.  You may find bullets are not perfect and you just need to load shorter to ensure the gun cycles safely.  Just stay clear of ever going shorter than your pupblished load data.

Edited by Livin_cincy
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Are you using mixed brass? What are the head stamps of the ones not passing?

 

I use a case gauge rather than the barrel. CBC brass caused enough rejects for me that I now sort it out ahead of time. The problem was at the base of the bullet and you could see scuff marks from the case gauge. I've read that the CBC case wall is thicker than others, which makes sense.

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Check the failures and see if they are the same brand of brass, as JS pointed out previously there are a few brands that usually don't work well.

 

If that turns out to be the case, just scrap all that brand, also scrap all the ones with a belt on the inside of the case.  Save all the unwanted brass and fired primers and sell to a local scrap dealer, don't just throw it away.

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On ‎5‎/‎6‎/‎2017 at 1:02 PM, 57K said:

Remember that all cases are not the same thickness. If you set up your dies for a single brand like WIN or R-P you may be loading cases like CBC that are thicker and may be over-diameter at the case-mouth. SAAMI MAX spec is .380" diameter at the case-mouth and it's really best to be a little under that. What thickness should they be? That's a simple matter of finding average thickness by brand by measuring within 1mm of the case-mouth, double that dimension and add bullet diameter. Your Acme coated are probably .356" in diameter or larger. Case-mouth diameter should not exceed .380" or they may not pass. Normally, you don't need to taper crimp with bullets that are .356" or larger in diameter, and personally, I'd want to have mine at .379" or less at the case-mouth. Taper crimp may be req'd if that's the case and I always taper crimp JHPs.

 

As an example with cases .011" or less thick, the formula would be .011" x 2 = .022" + Case-mouth diameter. If that's .356", that would put finished case-mouth diameter at .378" and you don't need to taper crimp after seating. Remove the flare during the seating operation to get the finished case-mouth diameter from the formula. But say a case is .012" thick. X 2 = .024" = .356" and your case-mouths are at the Max SAAMI spec and maybe over-diameter for your particular chamber. In that case, I would taper crimp them down to .379", or even .378" if necessary.

Good info here!

Thanks,

G

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The entire point of the plunk test is to determine whether a certain OAL with a certain bullet will chamber freely in your gun.  

 

Ideally, you want to do this at the BEGINNING of a reloading session with new bullets to determine the MAX OAL for that particular bullet and gun.  Determine the max oal for whatever combo you are using.  Then subtract at least .020" off the max OAL.  You should never have to worry about that particular load not chambering in your gun.

 

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7 minutes ago, 57K said:

You don't need to subtract so much from the Max Possible OACL. It's really about the OACL variation you get from your press and dies. All you need to do is establish some free-bore and so long as the bullet is not touching the rifling, you have at least a small amount of it.

 

When I can keep OACL tolerances around +/- ,001", I only subtract .005" for free-bore. If you're OACL variations run +/- .003" or more, it's safer to subtract .010" from the Max Possible OACL.

 

Depends on type of bullet and lot to lot variation.  I've seen coated bullets' ogive vary more than .005" from lot to lot.

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