9mm Reloads and Plunk Test

[Bravo1]

Hi All.

I've run into an odd situation while reloading 9mm in my Beretta 92.

I purchased a threaded barrel from Gemtech and noticed that for some reason, half of my reloads don't pass the plunk test in the new barrel. However, all reloads will pass in my factory barrel. When I spoke with the Gemtech Tech Support team, they indicated their barrels were "Match Grade" while the factory barrel had looser specs.

I'm using both 115g and 147g X-treme RN in once fired brass. The brass meets all the required specs for dimensions and are mixed headstamps of Federal, Winchester, S&B, PMC, etc. All were initially fired from my Beretta 92. But there is no rhyme or reason as to which will pass and which will fail the plunk tests. All were run through my Lee Progressive after it was calibrated for the correct bullet, bullet depth, powder charge, crimp, etc. One reload of FC will pass while the next will not and so on. I can't seem to find any consistency as to why this is happening. I essentially have to plunk each bullet and separate them into Factory barrel and Threaded barrel for use.

Any suggestions would be greatly appreciated.

 

[Jim Watson]

You have an undersize chamber. "Match Grade" is advertising, not a specification.

You can get it reamed to SAAMI or CIP spec, like your Beretta.
You can try a Lee CFC die to iron out your reloads with plated bullets.
You can seat bullets a bit deeper - reducing the powder charge if you are at maximum.

 

[74A95]

The first thing to do is to determine WHY they are not passing the test by using a magic marker.

That will help you determine the source of the problem and what needs to be corrected.

The method is explained here: http://www.shootingtimes.com/reloading/reloading-tips-the-plunk-test/

 

[Don P]

As stated, reduce OAL and if you can check concentricity. Another possibility is the olgive of the bullet. I have found some round nose bullets having to be set deeper so they do not nit the leading edge of the rifling. A more pointed bullet may solve the problem

 

[Metal god]

Yes you first need to figure out why it's failing the plunk test . The barrel may very well have a shorter lead/throat and the bullet simply needs to be seated little deeper . If the diameter of the chamber is tight then maybe a Lee FCD that has the carbide swaging ring in the base that swages the brass down to spec .

I believe you can have Lee make you specifically sized FCD to swage the cartridge down even smaller then normal if need be . The only issue I'd have with that is that the die swages the cartridge with bullet seated . So as it compresses the case the bullet gets squeezed down as well . The thing that can happen is with soft lead bullets or the like . The case springs back a little while the bullet does not reducing bullet hold .

 

[kmw1954]

I ran into this same issue with a new Springfield XD 9mm. All my loaded rounds would plunk test into my PT92 but not into the XD. As it turned out I was using a very light crimp when I loaded the 92. I turned the seating die down 1/4 turn and all was well. Bullets still seated to the 1.130" OAL.

 

[Bravo1]

Thanks all.

After using the pen test to see where it might be rubbing, it turns out it's on the body slightly above the head of the case. Wouldn't the sizing die catch and correct it? I readjusted the sizing die but it's still catching in the same spot. It's not the bullet since I've tested it with 115g and 147g and it's always below where the bullet is seated in the case.

I spoke with a buddy who's a gunsmith and reloader and he suggested that it might be a die issue so I ordered a Redding 9mm Die Set to see if that will help.

 

[muncie21]

Depends on how far above the case head you're talking about. If you look at how the shell sits in the press you'll see that you can't resize all the way to the case head, as the shell holder obstructs a portion of the case.

If the 'bulge' is higher up on the case, a new sizing die or adjusting the existing one down a bit may help.

 

[kmw1954]

The X-treme bullets are manufactured to .355" unlike the Berry's which are .356" so the bullet bulge should be slightly less.

The Lee dies are a taper crimp for the 9mm so they should size correctly. As I stated in post #6 I would try turning the seating die down 1/4 turn to increase the crimp before I would rush out and buy a new die.

Resize a case and try to "plunk it" before adding a bullet and see if it will seat.