Inconsistent Case Wall Thickness and Plunk Test

[LiveLife]

In recent years, I have noticed increase in case wall thickness inconsistencies that could affect the "plunk test".

Another "reloading variable" for us to consider.

If you use factory/aftermarket barrels with looser dimensions, you may not have noticed this but if you use barrels with tighter chambers and/or case gauge to check finished rounds, you may have experienced this already.

Referencing "Myth Busting Neck Tension and Bullet Setback" thread for case wall thickness .200" below case mouth (Where base of 115 gr FMJ/RN bullet would seat to and bulge the most amount of case neck), I selected several different headstamp cases to see how difference in case wall thickness can affect the "plunk test".


NOTE: All brass were sized, flared and sized again to straighten out the case mouth/neck for measurement.


RMR 115 gr FMJ was loaded to 1.120" OAL and tested in Lone Wolf 40-9 conversion barrel with the tightest chamber with shortest leade.


Winchester brass - Passed plunk test and fell out freely

• Freely fell in chamber with a "plonk" and spun without hitting the rifling
• Case wall measurements taken .200" below case mouth: .0125" - .0125" - .013" - .0125"
• Finished round OD at .200" below case mouth: .3795" - .3795" - .3795" - .3795"

R-P brass - Passed plunk test and fell out freely

• Freely fell in chamber with a "plonk" and spun without hitting the rifling
  
• Case wall measurements taken .200" below case mouth: .012" - .012" - .012" - .012"
• Finished round OD at .200" below case mouth: .3795" - .3795" - .3795" - .3795"

.FC. brass - Passed plunk test and fell out freely

• Freely fell in chamber with a "plonk" and spun without hitting the rifling
  
• Case wall measurements taken .200" below case mouth: .011" - .0115" - .0115" - .011"
• Finished round OD at .200" below case mouth: .3765" - .377" - .377" - .3765"

G.F.L. brass - Passed plunk test and fell out freely

• Case wall measurements taken .200" below case mouth: .012" - .013" - .013" - .0145"
  
• Finished round OD at .200" below case mouth: .379" - .380" - .3805" - .380"

AGUILA brass - #1 Passed plunk test and fell out freely

• Case wall measurements taken .200" below case mouth: .012" - .012" - .0125" - .0125"
• Finished round OD at .200" below case mouth: .3795" - .3795" - .3795" - .3795"

AGUILA brass - #2 Passed plunk test and fell out freely

• Case wall measurements taken .200" below case mouth: .0125" - .0125" - .013" - .0135"
• Finished round OD at .200" below case mouth: .379" - .379" - .3795" - .379"

PPU brass - Failed plunk test and stuck in chamber

• Failed to turn freely but chambered deep enough to headspace off extractor
• Case wall measurements taken .200" below case mouth: .0135" - .014" - .0145" - .0135"
  
• Finished round OD at .200" below case mouth: .382" - .382" - .3825" - .382"

Tulammo brass - Failed plunk test and stuck in chamber

• Case wall measurements taken .200" below case mouth: .012" - .015" - .016" - .013"
  
• Finished round OD at .200" below case mouth: .381" - .3815" - .3815" - .381"

• Case wall measurements taken .200" below case mouth: .0135" - .014" - .016" - .0155"
  
• Finished round OD at .200" below case mouth: .382" - .382" - .3825" - .382"

 

[WestKentucky]

I’m glad your here to analyze things that some of us never consider. I don’t know how you do as much as you do, to the depth and detail that you do it, and still manage to live life. I would suggest getting a hobby to take up free time, but I’m worried you would go headlong into it and then we would miss you and your love for your current hobby.

Now, looking at your results, does the concentricity of the neck significantly effect anything aside from the round chambering? I doubt it is much if any of a factor on accuracy because this minuscule flaw is at the chamber and a decent barrel will straighten it all out, but I do suspect that poor concentricity will exacerbate any work hardening of the necks and lead to splitting or loss of neck tension at an earlier time.

 

[snakeye]

bds

I'm interested in your opinion why the AGUILA failed when the Winchester and RP passed with almost identical measurements

 

[joneb]

I never considered case wall thickness for handgun cases, only for rifle. Thanks for the heads up

 

[LiveLife]

I apologize to everyone for adding one more reloading variable to your reloading life.

WestKentucky, wife says she rather see me fussing over shooting and reloading things than smoking and drinking as long as I keep cooking her favorite BBQ and baked beans.

I'm interested in your opinion why the AGUILA failed when the Winchester and RP passed with almost identical measurements

I wondered about that as well.

One thing I noticed from the "Myth Busting Neck Tension and Bullet Setback" thread was thicker walled cases experiencing bullet setback when thinner walled Starline/Winchester brass did not experience any bullet setback and commented this may be due to brass quality - https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-3#post-10715550

I plan to investigate this further but my guess at this point may be that Aguila case could be collapsing slightly and bulging below where bullet is being seated.

 

[LiveLife]

Update: Snakeye, I just chamber checked AGUILA and WIN rounds again and what I noticed is WIN round can wiggle in the chamber while AGUILA round can't.

 

[fxvr5]

I apologize to everyone for adding one more reloading variable to your reloading life.

WestKentucky, wife says she rather see me fussing over shooting and reloading things than smoking and drinking as long as I keep cooking her favorite BBQ and baked beans.


I wondered about that as well.

One thing I noticed from the "Myth Busting Neck Tension and Bullet Setback" thread was thicker walled cases experiencing bullet setback when thinner walled Starline/Winchester brass did not experience any bullet setback and commented this may be due to brass quality - https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-3#post-10715550

I plan to investigate this further but my guess at this point may be that Aguila case could be collapsing slightly and bulging below where bullet is being seated.

Update: Snakeye, I just chamber checked AGUILA and WIN rounds again and what I noticed is WIN round can wiggle in the chamber while AGUILA round can't.

You need to assess where they are sticking/rubbing. Once you do this, you'll know why some pass and some fail the plunk test.

Do you know how to determine this?

 

[LiveLife]

Yes.

This was my initial test. As with other myth busting threads, I will be conducting additional tests.

Stay tuned.

 

[fxvr5]

Yes.

This was my initial test. As with other myth busting threads, I will be conducting additional tests.

Stay tuned.

Does this mean yes or no to my question?

 

[LiveLife]

Yes.

 

[Blue68f100]

Update: Snakeye, I just chamber checked AGUILA and WIN rounds again and what I noticed is WIN round can wiggle in the chamber while AGUILA round can't.

Need to find the root cause for this. Cutting the brass in 1/2 may show the differences after you determine where it's contacting.

 

[SC_Dave]

In recent years, I have noticed increase in case wall thickness inconsistencies that could affect the "plunk test".

Another "reloading variable" for us to consider.

If you use factory/aftermarket barrels with looser dimensions, you may not have noticed this but if you use barrels with tighter chambers and/or case gauge to check finished rounds, you may have experienced this already.

Referencing "Myth Busting Neck Tension and Bullet Setback" thread for case wall thickness .200" below case mouth (Where base of 115 gr FMJ/RN bullet would seat to and bulge the most amount of case neck), I selected several different headstamp cases to see how difference in case wall thickness can affect the "plunk test".


NOTE: All brass were sized, flared and sized again to straighten out the case mouth/neck for measurement.


RMR 115 gr FMJ was loaded to 1.120" OAL and tested in Lone Wolf 40-9 conversion barrel with the tightest chamber with shortest leade.


Winchester brass - Passed plunk test and fell out freely

• Freely fell in chamber with a "plonk" and spun without hitting the rifling
• Case wall measurements taken .200" below case mouth: .0125" - .0125" - .013" - .0125"
• Finished round OD at .200" below case mouth: .3795" - .3795" - .3795" - .3795"

R-P brass - Passed plunk test and fell out freely

• Freely fell in chamber with a "plonk" and spun without hitting the rifling
  
• Case wall measurements taken .200" below case mouth: .012" - .012" - .012" - .012"
• Finished round OD at .200" below case mouth: .3795" - .3795" - .3795" - .3795"

.FC. brass - Passed plunk test and fell out freely

• Freely fell in chamber with a "plonk" and spun without hitting the rifling
  
• Case wall measurements taken .200" below case mouth: .011" - .0115" - .0115" - .011"
• Finished round OD at .200" below case mouth: .3765" - .377" - .377" - .3765"

G.F.L. brass - Failed plunk test and stuck in chamber

• Failed to turn freely but chambered deep enough to headspace off extractor
• Case wall measurements taken .200" below case mouth: .012" - .013" - .013" - .0145"
  
• Finished round OD at .200" below case mouth: .379" - .380" - .3805" - .380"

PPU brass - Failed plunk test and stuck in chamber

• Failed to turn freely but chambered deep enough to headspace off extractor
• Case wall measurements taken .200" below case mouth: .0135" - .014" - .0145" - .0135"
  
• Finished round OD at .200" below case mouth: .382" - .382" - .3825" - .382"

AGUILA brass - Failed plunk test and stuck in chamber

• Did not chamber deep enough to headspace off extractor
• Case wall measurements taken .200" below case mouth: .012" - .012" - .0125" - .0125"
• Finished round OD at .200" below case mouth: .3795" - .3795" - .3795" - .3795"

Tulammo brass - Failed plunk test and stuck in chamber

• Case wall measurements taken .200" below case mouth: .012" - .015" - .016" - .013"
  
• Finished round OD at .200" below case mouth: .381" - .3815" - .3815" - .381"

• Case wall measurements taken .200" below case mouth: .0135" - .014" - .016" - .0155"
  
• Finished round OD at .200" below case mouth: .382" - .382" - .3825" - .382"

I have noticed this not so much in my generous Glock chamber but definitely in my Shockbottle gauge.
SCD

 

[thomas15]

In the last 2 years, 90% of my handloads or approx. 10,000 per year are 9mm for my two S&W 929s which are 9mm revolvers. They are my competition revolvers with aftermarket parts and extensive trigger work. Without making any measurements, just going by performance, I have been able to isolate which headstamps work and which headstamps don't work.

There are, in those guns, two major issues. The first is cases sticking in the charge holes (all 8 cases attached to moon clips), the second is reliable primer ignition. Once loaded in the moonclips, each moon is placed into a moon clip checker. 99% of the .05% that fail at that point are due to rounds that are not fully seated into the moon clips. Easy fix then back into service. Some of my moon clips are very tight and most moon clips are headstamp specific. This means that there is another common variable in 9mm brass: the extractor groove dimension(s).

It is of course a given that some makers of brass for the 9mm market are more exacting than others as this is a competitive selling environment. I personally have something like 50,000 pcs of fired 9mm brass. I took me many months to sort through it all and put into separate containers based on headstamp. And then it's still not over, keeping/maintaining everything separate is also a chore. I have approx. 12,000 federal, 8,000 blazer, 10,000 Winchester and the rest, about 20,000 is mixed brass. I have a system worked out for keeping everything organized. This takes time, a lot of time and is one of several other reasons why I cannot perform my handloading operations on anything other than a reliable progressive press. I still work full time and have other interests besides firearms, family commitments, volunteer firefighter/EMT,committed DIYer.

One of my two 929s is a little less picky than the other, it is due to a difference in revolver headspace. So for my open gun, I use only Winchester brass and .040 moon clips, for the other (iron sight) gun any of the 3 mentioned headstamps with .035-.040 moon clips but the .040 are a little tight in that gun. In all of those guns I use a EGW undersize die and 38 (.358) coated bullets. And of course only federal primers seated below flush, actually they are bottomed out. The 38 bullets are a tight fit in the case but pass the case gage whereas even standard 9mm (.355) bullets will fail if something else is wrong. It's that something else that can cause all the headaches. I do, btw, an AQL (batch) test of all of my bullets when I get them. Even premium bullets have variations. This operation (AQL testing) is of course for my personal amusement as I'm not a honcho on the competition action pistol circuit.

Any deviation from the above (both procedures and dimensions) will cause either mis-fires or case sticking in the cylinder. In my opinion, there are other factors in case performance just not case thickness variables. Deep seat enough primers and you will come to recognize some of those variables. But as far as the case makers are concerned they are only worried about meeting SAAMI specs for the first firing. We all love a bargain at the checkout counter forgetting that in the end we get what we pay for.

For my other 9mm, semi-auto Glocks (G17, G26), S&W (M&P and 6900 series) I use the mixed brass and don't obsess over recovery of fired cases. If those handloads fit the case gage then they will fire fine in those guns. While I get 99-100% success in my handloads (case gage pre-firing), I can personally live with a reject rate of about 2% that don't pass the gage. This is without resorting to any kind of forced resizing after the bullet is seated and crimped.

All to say that case wall thickness is one of many factors that affect our handloads. The OP makes a good case for case thickeness as a performance issue. Not mentioned is, and I believe but cannot prove, that some brass in addition to being a certain thinkness are also harder or softer alloy than others. All things being equal, this also can have it's effect on performance. It really comes down to just what is it we expect from our handloads and how much time/effort/money are we willing to put into this endeavor. Making all of the measurements is fine and gives us a correlation starting point, but it is experimentation that will determine what our particular application requires. Overall the OP makes some very good observations.

 

[kcofohio]

That is why I have sorted by headstamp for some time.
PMC (Korean, IIRC) and CBC brass were usually thicker walled and PMC varied a few thousandths side to side.
I crumpled a few PMC cases when using the seating die to crimp, because of them being up to .004" thicker than say WIN brass. They would touch the crimping contour before the other brass.

 

[Toprudder]

There are variations - some rather large - in how the case walls taper in thickness. Most of the brass I checked at one point had a fairly consistent wall thickness starting at the mouth and down to about .200". From there, the walls increased in thickness down to the web. At least one headstamp (I would have to look at my notes) started tapering in thickness at the case mouth. And the thicknesses tapered more than others. I suspect this is where the problem could be when two headstamps have case walls that measure the same but one passes plunk and the other doesn't.

The problem will be more apparent with 147gn bullets that have the base of the bullet seated farther down in the case than with 115gn bullets.

 

[Ireload2]

Your observations may work for your individual barrel.
But you do not appear to have measured the chamber to know if your chamber falls within SAAMI standards.
There is little chance of a problem if you only have one gun and one barrel. If you have multiple barrels and pistols in the same caliber you might want to use the smallest chamber or a real gage to insure that the ammo fits everything.

In recent years, I have noticed increase in case wall thickness inconsistencies that could affect the "plunk test".

Another "reloading variable" for us to consider.

If you use factory/aftermarket barrels with looser dimensions, you may not have noticed this but if you use barrels with tighter chambers and/or case gauge to check finished rounds, you may have experienced this already.

Referencing "Myth Busting Neck Tension and Bullet Setback" thread for case wall thickness .200" below case mouth (Where base of 115 gr FMJ/RN bullet would seat to and bulge the most amount of case neck), I selected several different headstamp cases to see how difference in case wall thickness can affect the "plunk test".


NOTE: All brass were sized, flared and sized again to straighten out the case mouth/neck for measurement.


RMR 115 gr FMJ was loaded to 1.120" OAL and tested in Lone Wolf 40-9 conversion barrel with the tightest chamber with shortest leade.


Winchester brass - Passed plunk test and fell out freely

• Freely fell in chamber with a "plonk" and spun without hitting the rifling
• Case wall measurements taken .200" below case mouth: .0125" - .0125" - .013" - .0125"
• Finished round OD at .200" below case mouth: .3795" - .3795" - .3795" - .3795"

R-P brass - Passed plunk test and fell out freely

• Freely fell in chamber with a "plonk" and spun without hitting the rifling
  
• Case wall measurements taken .200" below case mouth: .012" - .012" - .012" - .012"
• Finished round OD at .200" below case mouth: .3795" - .3795" - .3795" - .3795"

.FC. brass - Passed plunk test and fell out freely

• Freely fell in chamber with a "plonk" and spun without hitting the rifling
  
• Case wall measurements taken .200" below case mouth: .011" - .0115" - .0115" - .011"
• Finished round OD at .200" below case mouth: .3765" - .377" - .377" - .3765"

G.F.L. brass - Failed plunk test and stuck in chamber

• Failed to turn freely but chambered deep enough to headspace off extractor
• Case wall measurements taken .200" below case mouth: .012" - .013" - .013" - .0145"
  
• Finished round OD at .200" below case mouth: .379" - .380" - .3805" - .380"

PPU brass - Failed plunk test and stuck in chamber

• Failed to turn freely but chambered deep enough to headspace off extractor
• Case wall measurements taken .200" below case mouth: .0135" - .014" - .0145" - .0135"
  
• Finished round OD at .200" below case mouth: .382" - .382" - .3825" - .382"

AGUILA brass - Failed plunk test and stuck in chamber

• Did not chamber deep enough to headspace off extractor
• Case wall measurements taken .200" below case mouth: .012" - .012" - .0125" - .0125"
• Finished round OD at .200" below case mouth: .3795" - .3795" - .3795" - .3795"

Tulammo brass - Failed plunk test and stuck in chamber

• Case wall measurements taken .200" below case mouth: .012" - .015" - .016" - .013"
  
• Finished round OD at .200" below case mouth: .381" - .3815" - .3815" - .381"

• Case wall measurements taken .200" below case mouth: .0135" - .014" - .016" - .0155"
  
• Finished round OD at .200" below case mouth: .382" - .382" - .3825" - .382"

 

[LiveLife]

Your observations may work for your individual barrel.

But you do not appear to have measured the chamber to know if your chamber falls within SAAMI standards.

That was my initial reaction but then why did WIN, R-P and .FC. rounds all pass the plunk test? (And based on my experience with this barrel, most other domestic headstamp brass will pass also).

If WIN/R-P/.FC. failed the plunk test also, I would question the barrel's chamber dimensions but since they did not, I shifted my focus to brass that failed the plunk test. My sentiment is the Lone Wolf barrel with tightest chamber from several I have along with KKM barrels may have SAAMI minimum chamber, like some case gages and may experience similar results and why I started this thread, to inform reloaders another reloading variable to consider when their finished rounds do no pass the "plunk test" in their barrels with tighter chambers or cage gages.

BTW, all the rounds passed the plunk test in my other Lone Wolf and KKM barrels (but they have more looser dimensions with longer leades).

 

[fxvr5]

Do sized, empty cases from all brands pass the plunk test? Would need to test many examples of each.

Have you determined why the ones that failed, did fail?

 

[LiveLife]

Do sized, empty cases from all brands pass the plunk test? Would need to test many examples of each.

Very good points.

Yes, when I first started noticing the finished rounds not passing the "plunk test", first thing I did was to chamber check resized brass to make sure I was full-length sizing them. I have my dies set so the bottom of Lee sizer barely kisses the top of shell plate without daylight. All the headstamp brass passed.

That's why I started investigating the case wall thickness, not at .100" below case mouth but at .200" below case mouth where the bullet base of 115 gr FMJ would bulge more of thicker case walls to rub with the chamber wall.

 

[fxvr5]

That's why I started investigating the case wall thickness, not at .100" below case mouth but at .200" below case mouth where the bullet base of 115 gr FMJ would bulge more of thicker case walls to rub with the chamber wall.

Is that where they are rubbing/sticking? Have you used a magic marker to determine this?

 

[LiveLife]

No, not with the AGUILA round but other rounds that measured more than .381" at .200" below case mouth show rub mark.

Have you determined why the ones that failed, did fail?

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.

Stay tuned.

 

[fxvr5]

Sounds like you need to measure the base, too.

The magic marker will tell you EXACTLY where the cases (or bullets) are rubbing.

 

[fxvr5]

one last question. were all these cases previously fired in the same chamber?

 

[thomas15]

bds, don't take this the wrong way. Without taking away from any of the hard work you have performed and in spite of your response to him, I do believe that Ireload2 makes a valid point, one that while not in exact detail but in a similar mode of thought, I considered making.

I didn't for two reasons, the first is you are attempting to use a valid system to make your observations which is rare in these parts and second, you certainly put a lot of time into this. I commend you on having the control sample lots however what you are proving or disproving is still based not on "standards" but rather on your specific gun barrels and your particular "environmental" conditions which might be somewhat different than my gun barrels and conditions.

This is the reason why in my post #12 I wrote "it is experimentation that will determine what our particular application requires."

The truth of the matter is the tolerances in the SAAMI spec are big enough to drive a semi-truck through. The materials and hardware that most of us have to work with also have large tolerances. This is the reason why Distinguished Master shooting a $3500.00 match pistol has an occasional jam with handloads while the hapless beginner with a Glock 19 shooting Winchester white box ammo runs flawless.

But still you did a nice job and provided us with plenty of food for thought. I don't want to take that away from you. However I would caution anyone from making hard and fast conclusions from your observations. I can and have made handloads that work flawless from brass you conclude is beyond hope, conversely, I have had duds from brass you find adequate.

 

[LiveLife]

If you use factory/aftermarket barrels with looser dimensions, you may not have noticed this but if you use barrels with tighter chambers and/or case gauge to check finished rounds, you may have experienced this already.

thomas15, I am doing this for members who have tight chamber barrels and those who wonder why some finished rounds do not pass the case gage and for them to consider additional reloading variable of case wall thickness at .200" below case mouth.

As I already posted, those using barrels with more generous chambers do not apply to this thread.

Sounds like you need to measure the base, too.

Funny you mention that. I am actually resizing brass and measuring base as I type this.

Stay tuned for the results.

were all these cases previously fired in the same chamber?

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