Plunk test

[Black wallnut]

Originally Posted by Nathan

I’m not sure we are all getting what the “plunk” test is and why use it. You drop the round in and the headspace feature, the mouth of an auto round. Hits the end of the chamber. You shorten the round until the bullet doesn’t touch the rifling. This ensures that an auto pistol round does not hang up in the rifling when fed. If it sticks, you can pull the case off the bullet and jam up the whole gun.

I disagree with your description. The plunk test is used in auto pistol barrels making sure the round chambers so that the base is even with or shorter than the hood. That's it. That insures that if it feeds it will go into battery. It also proves that your ammo is not oversize when compared to the chamber.

Furthermore I agree with @Unclenick in his description of typical straight wall pistol cartridge headspace. Although the spec is for headspace on the case mouth that almost never happens as straight wall cartridges shorten with each firing.

For .45 ACP I use a new barrel to check reloads. I have found that the chamber in the new barrel is at least as tight as my pistols. If the reloads drop into the new chamber then they will fit in my pistols. Feeding is a different issue and I am lucky in that both bullet profiles that I use (lead SWC) run in both guns I currently have. I have previously had guns that just would not feed one or the other of the two I use. I could maybe improve accuracy by loading for each individual pistol but I don't allocate the time for that.

[stagpanther]

^^^that's what I've understood it to be for^^^^^

[cdoc42]

I think Nathan and Black Walnut are saying the same thing.

Here’s another way to look at it:

If you “plunk” a finished cartridge and the base of the case is even with the hood of the barrel, the case has headspaced properly on the mouth of the case and the bullet is not engaged in the rifling.

If the cartridge is too high, either the case is too long or the bullet is not seated deeply enough and has engaged the rifling. If you know your case lengths fall between the SAAMI maximum and “trim to” measurements, then the seating depth of the bullet is the problem.

As Black Walnut pointed out, generally the cases shorten when fired, but I’m not certain that is an issue because I have noticed resizing the case lengthens it again. At least in the 9mm cases I have measured before and after resizing, and I have never resized a case where it is longer than the maximum 0.754”.

If the cartridge “plunks” too deeply, the case is too short and the headspace is insufficient. It can’t be a bullet seating depth problem.
But I have to wonder how commonly this occurs unless one trims the case too short.

One other possibility is also virtually impossible. The case is too short but the bullet is seated far enough out and into the rifling that the “plunk” test has the case exactly even with the hood. Again, are short cases common?

[Nathan]

I disagree with your description. The plunk test is used in auto pistol barrels making sure the round chambers so that the base is even with or shorter than the hood. That's it. That insures that if it feeds it will go into battery. It also proves that your ammo is not oversize when compared to the chamber.

Furthermore I agree with @Unclenick in his description of typical straight wall pistol cartridge headspace. Although the spec is for headspace on the case mouth that almost never happens as straight wall cartridges shorten with each firing.

For .45 ACP I use a new barrel to check reloads. I have found that the chamber in the new barrel is at least as tight as my pistols. If the reloads drop into the new chamber then they will fit in my pistols. Feeding is a different issue and I am lucky in that both bullet profiles that I use (lead SWC) run in both guns I currently have. I have previously had guns that just would not feed one or the other of the two I use. I could maybe improve accuracy by loading for each individual pistol but I don't allocate the time for that.

First, I appreciate your disagreement.

Is base to hood a known dimension? What is it related to? Generally the hood is hard fit to the breech face or it appears so, but in reality, there is always a slight breech face to hood gap(not visible because gap is forced to the barrel lug end) and still have a functioning gun. I think we never see it because the spring closes that gap and most auto cases are short. With a long case, and poor lug to breech length, you could have a gap on an in spec gun/ammo, I believe. Not normal, I agree.

If you “plunk” a finished cartridge and the base of the case is even with the hood of the barrel, the case has headspaced properly on the mouth of the case and the bullet is not engaged in the rifling.

Sort of…with a proper plunk, you hear the case hit the chamber. If the bullet hits the lands, there is no plunk sound. Also, when flipped over, it should fall out without holding the lands at all. Too long, the bullet hangs up on the lands. Too short….well, it won’t tell you that. Case too long, it sort of shows this, but that is more of a gross check….like it is 0.01” too long and you spot it above the hood. Maybe the case is too long, maybe hood too short. Regardless 0.01” is a mile. Case length is a caliper check.

[Jim Watson]

In auto pistols, the usual clanger is the chamber throat/leade and bullet ogives. Seems like the gunmakers usually do OK on the chamber - unless you fall into the Minimum Match Chamber trap - but throats are rather variable. And there is no spec for bullet noses at all. I can tell a difference from gun to gun but it seldom affects the load. Seldom not never, I have one lot of ammo that I will have to shoot in one particular gun.

Back in the previous century, when cast semiwadcutters were usual fare for .45 ACPs, we commonly loaded them to "headspace" on the shoulder of the bullet, seating so that a plunk left the case head even with the barrel hood. Case length and extractor engagement were not a factor.

[HiBC]

Considering the barrel to slide locking lug contact, should the hood be hard fitted to contact the breech face at full battery?

[georgehwbush]

( there is "Reloading" and there is "Handloading" )

well i am a handloader, and seeing that i have never baught any empty brass; that makes all my handloads, reloads.

but yeah to the origenal question, i load mostly bottleneck rifle cartridges, and the "PLUNK" test does what it does, it tells me if the cartridge will chamber or balk before it gets there. so i use the plunk test every time i change the specs on any load.

so yeah.

[Unclenick]

Originally Posted by Jim Watson

Back in the previous century, when cast semiwadcutters were usual fare for .45 ACPs, we commonly loaded them to "headspace" on the shoulder of the bullet, seating so that a plunk left the case head even with the barrel hood. Case length and extractor engagement were not a factor.

Presactly!

Originally Posted by HiBC

Considering the barrel to slide locking lug contact, should the hood be hard fitted to contact the breech face at full battery?

The slide usually pushes on the hood (aka, barrel extension) to make the barrel slide up into battery, so contact is made.

[cdoc42]

In contrast to rifle handloading, I gather little attention is paid to the distance a handgun bullet has to jump to engage the rifling as a method to determine accuracy. Maybe the usual target distance of 15 yards or less is a factor, leaving us with no more than a concern that the seating depth should not be long enough to prevent proper battery engagement nor too short to create dangerous pressure situations.

I suspect that I’m not alone when I look for a recipe that utilizes a 115gr bullet for my 9mm and I follow the directions that include the OAL of the finished cartridge, and assume that OAL will be safe in my pistol as long as the “plunk” test is passed. Is it really that simple?

But this does raise a question as to how the various reloading handbooks establish the recommended OAL in the various recipes. What follows is an example of the advice often given by 44AMP that various methods and advice need to be used with caution because the gun in the handbook is not necessarily going to work in YOUR gun.

Here are recipes for 9mm 115gr bullets from the various handbooks I’ve accumulated.

The Lyman 50th Ed. lists a Hornady 115gr HP/XTP having an OAL of 1.090.” I’ve loaded that without even considering that they didn’t use a Walther PPQ.

So I checked a few others, and NONE of them used the same pistol that I have:

Hodgdon #27: SPR GDHP 115gr OAl 1.125”

Speer #12: SPR GDHP 1.125” – TMJ 1.135” – JHP 1.125”

Hornady 4th Ed – (differs from Lyman) 115gr HP/XTP OAL 1.050” – FMJRN 1.105”

Nosler #3: lists loads for 90gr and 115gr unnamed bullets and gives the same OAL of 1.100” for both bullets.

Now here’s something that makes it even more complex. I have a box of Factory LAX 115gr RN with an OAL of 1.150” – and I have a bottle of the same 115gr X-Treme bullets. The bullet itself has a base-to-tip measurement of 0.552”. Using a .35 caliber comparator, I measured the base to “ogive” as 0.232”.

I have Precision Delta 115gr HP that has an OAL of 0.551” and the base-to-ogive is 0.273”.

I have Everglades 115gr HP that has an OAL of 0.558” and a base-to-ogive of 0.242”.

If I load all of these to the same OAL length, is it reasonable to assume they will not be equally accurate simply because the bullet jumps will differ?

Well, I just arbitrarily chose to mimic the LAX measurement for my X-treme bullets and I made 10 rounds at 1.150”. Then I made 10 P.Delta rounds at 1.100” and 10 of the Everglades at 1.125.” They all passed the “plunk test.

I fired them at 15 yards from the bench at a 6-inch white paper plate with a 4-inch green dot.

Evergreen was the winner with a 2.25” group with all 10 shots in the green dot.
Precision Delta put 5 in the green, 4 in the surrounding white plate and 1 was a complete miss.
X-treme put 7 of the 10 in the green and 3 in the white plate.

I wondered if the space for the powder plays a significant role. I did a few calculations and determined the Everglades load had 0.569” of powder space. The X-treme was 0.598” and the P. Delta was 0.549.” My next experiment will be to make the OALs whatever it takes to leave the same powder space under each bullet. Stay tuned.

[74A95]

Originally Posted by cdoc42

If I load all of these to the same OAL length, is it reasonable to assume they will not be equally accurate simply because the bullet jumps will differ?

Well, I just arbitrarily chose to mimic the LAX measurement for my X-treme bullets and I made 10 rounds at 1.150”. Then I made 10 P.Delta rounds at 1.100” and 10 of the Everglades at 1.125.” They all passed the “plunk test.

I fired them at 15 yards from the bench at a 6-inch white paper plate with a 4-inch green dot.

Evergreen was the winner with a 2.25” group with all 10 shots in the green dot.
Precision Delta put 5 in the green, 4 in the surrounding white plate and 1 was a complete miss.
X-treme put 7 of the 10 in the green and 3 in the white plate.

Accuracy testing is at best, not always reliable. You can get very different 10-shot group sizes even when using the exact same ammo. Below is an article that looks at this issue.

https://www.ssusa.org/content/accura...-in-the-group/

[cdoc42]

Near the end of that link, the author said:

"Fifty-shot groups seem like they should be more than enough to tell you how your gun likes the ammunition, but we learned that even 50-shot groups with the same ammo can be different sizes."

So I can't fly like a bird unless I am a bird, and even then, birds fly differently?

From a rifle history, I can say I may not be able to get a 0.7-inch group with 5 shots from my 6mm PPC every time I go to the range, but it invariably beats the 1.0-inch group that I just as often get with my 6.5mm Creedmoor.

Regarding the experiment I described, if the Everglade bullets provide a better group, size notwithstanding, than P. Delta and X-treme, the size doesn't matter.

[74A95]

Originally Posted by cdoc42

Regarding the experiment I described, if the Everglade bullets provide a better group, size notwithstanding, than P. Delta and X-treme, the size doesn't matter.

You missed the point.

[44 AMP]

In contrast to rifle handloading, I gather little attention is paid to the distance a handgun bullet has to jump to engage the rifling as a method to determine accuracy.

Bullet jump to the lands is one factor that can affect accuracy. Its a big deal (to some people) shooting rifles, but that's because rifles, generally, have fewer factors involved, or those factors have a lesser effect, simply because of the way the rifle is made.

First off, many semi auto pistols have barrels that move, in relation to the sights. That single factor can be more dominant for accuracy than bullet jump to the lands is.

And, you can't exactly do the rifle shooter's "chasing the lands" if you're shooting a revolver.

Also, things that are not the ammunition affect the "shootability" of handguns compared to rifles, and have an effect on the accuracy when the gun is fired by a human being.

The industry standard maximum loaded length for the 9mm Luger round is 1.169". That is from cartridge base to bullet tip. This number is derived from the original loadings (which were the only loadings commercially available for nearly 3/4 of a century) which used a fairly long nosed, fairly pointed FMJ RN.

Consider this, when dealing with bullets of equal weight, the hollow point is going to be shorter than the RN. When seated with the same amount of bullet in the case the HP will have a shorter overall loaded length. And lighter bullets are going to be shorter still.

I fired them at 15 yards from the bench at a 6-inch white paper plate with a 4-inch green dot....

Precision Delta put 5 in the green, 4 in the surrounding white plate and 1 was a complete miss.

You missed a 6" plate at 15 yards, firing from a bench, and it's the bullet's fault?? IF that's the cause, you need better bullets.

[georgehwbush]

44amp; admittedly i am not a pistole kind of guy, but did i understand correctly "of the same weight a hollow point bullet will be shorter than a round nose" ?

it may be general design normal, but it sounds counter intuitive. are they generally designed that way "shorter + fatter" ?

[74A95]

Originally Posted by georgehwbush

44amp; admittedly i am not a pistole kind of guy, but did i understand correctly "of the same weight a hollow point bullet will be shorter than a round nose" ?

44AMP is correct, with the only caveat being they are both from the same manufacturer.

[mehavey]

AutoPistols:

Hollow "PLUNK" sound base even or slightly under the barrel hood extension edge/falls out of barrel when upside down: Safest "general" bet that the assembled cartridge will fit/function not jam.

Assembled cartridge base even w/ barrel hood when pressed fully home -- and while "sticky"/not falling out can still be picked out w/ finger nails -- likely best accuracy.

Assembled cartridge base even w/ barrel hood when pressed fully home -- and can only be removed with cleaning rod: Incipient bad JuJu.

Assembled cartridge base past/beyond barrel hood when pressed fully home -- and can only be removed with cleaning rod: DEFINITE bad JuJu. Jammed gun.

[44 AMP]

44amp; admittedly i am not a pistole kind of guy, but did i understand correctly "of the same weight a hollow point bullet will be shorter than a round nose" ?

it may be general design normal, but it sounds counter intuitive. are they generally designed that way "shorter + fatter" ?

Yes.

(time for one of Uncle Nick's excellent illustrations )

Look at a bullet and note the basic parts and the terms used. From the bullet base up, the bullet has straight sides and if full bore diameter. This is the "body/shank/ bearing surface" etc. This is the part that contacts the rifling.

Then the bullet reduces diameter, from full bore diameter down to the tip. It may be a straight slope, or it may be some kind of curved slope. This section of the bullet is called the ogive (and it is the entire distance from the straight "shank" down to the tip). It does not contact the rifling, because it is smaller in diameter than the bore size. The actual bullet tip area is called the "meplat"

Now, take a regular RN or pointed bullet shape of a given weight. Lets use 9mm FMJ for example. How do you make that a hollow point??

You cut off the tip (and a bit) and "remove" some of the lead to make the hollow part. But removing that metal makes the bullet lighter as well as shorter.

TO maintain the weight, what is done is that the ogive is slightly changed, making the sloped nose section slightly "fatter" than the FMJ, allowing the room to "add back in" the weight of the material removed to create the hollow point, so the result is a hollow point of the same weight as the FMJ, but with a slightly "fatter" (wider in diameter) nose section than the FMJ has. The ogive portion of the bullet still does not contact the rifling, the bearing surface of the bullet is not changed, only the width of the nose.

Different makers do it slightly differently from each other, but this is the general concept.

This is why a 115gr FMJ and a 115gr JHP can have the same amount of bullet seated inside the case, but different overall loaded lengths.

For an obvious example, take any Spitzer and RN rifle bullet of the same weight and compare them. The nose of the spitzer is "long and skinny" the same weight RN bullet nose is thicker and shorter compared to each other. Same weight, just different lengths and shapes where the bullet doesn't touch the barrel.

Hope this helps.

[georgehwbush]

didn't help a bit. just asked if that was common, not how it happened. already knew that. also know the round nose and hollow point could be same length or even reverse with the hollow point being longer, it all depends on the way it's shaped ^ only asked if it was normal for pistol bullets to be hp= shorter than rn. so thanks.

[44 AMP]

ok, sorry for covering what you already knew, but its possible some other reader might benefit from the information.

In general, yes, its is common for pistol bullet hollowpoints to be shorter than RN designs of the same weight.

Common, but not the only way they are made.

[georgehwbush]

cool, see i learned something new, AGAIN!