Inconsistent Case Wall Thickness and Plunk Test

[fxvr5]

No, they are "mostly once-fired" from indoor range. I am resizing them for the first time.

Then these cases might be failing for reasons other than having thick walls. They might be failing because they have expanded too much around the base from being fired in a loose chamber, and they might be failing the plunk test because of being too wide at the base.

With all due respect, this invalidates your "thick case wall" comparison because you're looking at the wrong thing.

 

[LiveLife]

Different headstamp cases were resized and they all fully chambered in the barrel with loose rattle.

Here are their average measurements at case base forward of extractor groove:

• AP 15 - .386"
• FC - .386"
• WMA 14 NATO .386"
• A USA - .387"
• CBC - .387"
• Starline - .387"
• WIN - .387"
• GECO - .3875"
• GFL - .3875"
• R-P - .3875"
• AGUILA - .388"
• BLAZER - .388"
• .FC. - .388"
• PERFECTA - .388"
• PPU - .388"
• Tulammo - .388"
• IMI - .389" (crimped primer pocket)
• HRTRS - .3895"

 

[fxvr5]

Okay, let's say you use these new cases for your comparison. You have to ensure that the bullets are being seated perfectly square so that a lopsided seated bullet does not cause a lopsided bulge in the case. This could produce a bulge that might fail the plunk test, not because the case wall is thick but because the bullet is at a wonky angle.

I refer you to this article that discusses seating bullets at a 'straight' angle in 9mm brass: https://americanhandgunner.com/exclusive-crooked-seated-bullets-and-accuracy/

That author claims that only one seating die appeared to be able to guarantee straight seated bullets, the Redding competition seating die.

Ideally you should start with virgin brass so that you don't have to account for any other factors, such as excessive bulge from being fired in a loose chamber.

 

[LiveLife]

The AGUILA case that failed the "plunk test" was examined closely and when slight pressure was applied, would fully chamber with no movement of the case base against the chamber. The round would not fall out freely and had to be pulled out.

In comparison, WIN/R-P/.FC. rounds rattled loose inside the chamber with noticeable gap between the case base and the chamber wall.

At this point, I am suspecting case base contact with chamber wall as the cause for failing the "plunk test" but will be testing other AGUILA cases.

The case base of AGUILA was measured at .388", same as second case.

AGUILA brass - #2 Barely passed plunk test

• Resized brass rattled loose in the chamber
• Round did chamber fully but required a slight push with finger
• Round did rotate (with a lot of effort) without hitting the rifling
• Case wall measurements taken .200" below case mouth: .0125" - .0125" - .013" - .0135"
• Finished round OD at .200" below case mouth: .379" - .379" - .3795" - .379"

Interesting note - After I force chambered the first AGUILA round and rotated by force, it now drops in freely with a "plonk" but case base is tight against the chamber with no play and will fall out with a little tap on the barrel. The second AGUILA round after force chambered and rotated by force, now also drops in freely with a "plonk" and has slight wiggle with the chamber and will fall out with a little tap on the barrel.

 

[fxvr5]

AGUILA brass - #2 Barely passed plunk test

• Resized brass rattled loose in the chamber
• Round did chamber fully but required a slight push with finger
• Round did rotate (with a lot of effort) without hitting the rifling
• Case wall measurements taken .200" below case mouth: .0125" - .0125" - .013" - .0135"
• Finished round OD at .200" below case mouth: .379" - .379" - .3795" - .379"

Where is it rubbing? We can't interpret your results until we know this. Please do the magic marker thing described at this link: http://www.shootingtimes.com/reloading/reloading-tips-the-plunk-test/

 

[LiveLife]

Did the magic marker test on both rounds and first round showed slight rub mark around base of bullet (could be from insertion) but both showed sliver of brass around case mouth.

I seated the bullet seating/crimp die deeper by 1/8th of turn and ran the rounds again. They are now falling out freely.

So I ran the other failed rounds and while G.F.L. now passes the plunk test, no change for PPU and Tulammo.

 

[fxvr5]

Did the magic marker test on both rounds and first round showed slight rub mark around base of bullet (could be from insertion) but both showed sliver of brass around case mouth.

I seated the bullet seating/crimp die deeper by 1/8th of turn and ran the rounds again. They are now falling out freely.

So I ran the other failed rounds and while G.F.L. now passes the plunk test, no change for PPU and Tulammo.

Yup. Your method was flawed.

Now determine where the PPU and Tulammo are rubbing.

 

[LiveLife]

Just did that and they are rubbing the chamber at case neck where bullet base is seated to and case mouth even after running through the seating/crimping die again. The thicker case walls are bulging the case neck to case mouth and contacting the chamber wall.

I updated my OP to reflect the seating/crimping die adjustment.

 

[LiveLife]

Yup. Your method was flawed.

Guilty as charged!

I have checked the die setting previously and just goes to show you can't assume anything.

Still, the objective of the thread remains as thicker walled cases are affecting the plunk test by bulging the case neck where the bullet base is seated to.