9mm Plunk Test Fail

Tatershooter

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Is it possible for a reloaded round to pass a plunk test in one barrel and fail in a different barrel? Both are M&Ps, one a 9c and the other a 2.0 FS 4.25". I bought both guns used but they looked brand new.
 
Which barrel passed?
 
Yep.
Even same make/model/year, there's almost certainly more than one tool running on the line cutting chambers and they wear and parts get changed at different times.
2.0s were supposed to address the accuracy issues of first gen M&P 9mms, wouldn't be surprised at all to find a tighter chamber, with a shorter leade. Wouldn't suspect anything if it was the other way around, just wouldn't have expected it.
 
Which barrel passed?
The rounds that fail in the 4.25" barrel will pass in the 9c barrel. It all started with the slide locking up, not going in battery, by maybe 1/8" to 3/16". Measured everthing I know to measure which is not much, but seemed ok. Thought at first it was the blue bullets I was using but after the passing the plunk test on the 9c I'm not so sure. I'm new to reloading 9s, never had this problem with approx. 4k rounds of .40.
 
Does the finished round pass a case gauge?
Does a micrometer show there is a bulge at the top around where the bullet is seated?
I had some issues like this and ended up trying a Lee Factory Crimp and it fixed it. Not because it crimped better, but because it resized most of the case again after the bullet was seated and slightly expanded the case around the seated bullet.
 
slightly expanded the case around the seated bullet.

Please elaborate on this. Are you talking about the loosening of the bullet when too much crimp is applied because the brass springs back more than the bullet when compressed?
 
JimP42, I do not have a case gauge, that is why I was using the barrels. Not so much a bulge around the top, but on some rounds, especially some of the ones that fail, there is a slight bulge on about 1/3 of the side where you can see the outline of the bullet but is straight on the other side. It's not all the way around.I picked up on this when I used a Sharpie to color the bullet and then forced it to seat completely and saw the clean spot where the tight spot was when I removed the bullet. I am using the Lee Factory Seating and Crimping die. So you think it might help if I back-off the crimping and crimp in a seperate step?
 
Please elaborate on this. Are you talking about the loosening of the bullet when too much crimp is applied because the brass springs back more than the bullet when compressed?
I mean that the bullet literally expanded the brass as it was seated. Just barely enough to matter. Probably a somewhat tight (but in spec) chamber.

Take your calipers and close them on the loaded brass between the rim and seated bullet. After that, can you slide the calipers up past the mouth of the brass?
 
I mean that the bullet literally expanded the brass as it was seated. Just barely enough to matter. Probably a somewhat tight (but in spec) chamber.

Take your calipers and close them on the loaded brass between the rim and seated bullet. After that, can you slide the calipers up past the mouth of the brass?

I misunderstood your statement and thought you were saying the die expanded the case rather than the seating of the bullet expanding the case. Makes sense now. Thanks.
 
This is thread drift but its alwaysca better strategy to debug your process than to iron over the problem with a FCD. It brings other issues with it.

ETA that hourglass shape is not a problem so long as it passes the case guage

To the OP:

Dont set oal by the book. Set your COAL by plunking in all your guns. Choose a length that works in all of them and then find book data that matches.
 
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JimP42, I do not have a case gauge, that is why I was using the barrels. Not so much a bulge around the top, but on some rounds, especially some of the ones that fail, there is a slight bulge on about 1/3 of the side where you can see the outline of the bullet but is straight on the other side. It's not all the way around.I picked up on this when I used a Sharpie to color the bullet and then forced it to seat completely and saw the clean spot where the tight spot was when I removed the bullet. I am using the Lee Factory Seating and Crimping die. So you think it might help if I back-off the crimping and crimp in a seperate step?

Definitely try that. The FCD (is not a seater and) runs a carbide ring down the loaded round almost to the base and resizes it again, which should remedy your bulge.

That said, a lot of seating dies have a stem that flips around. Make sure you are using the appropriate one for the bullet shape you are seating. It seems odd that it would seat them that crooked.

Oh, and unload some of the offending rounds and look in the brass. Are they all using that infernal cursed brass that has a step inside? If so, well, there you go. Don't load those bullets that deep in the stepped brass.
 
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you think it might help if I back-off the crimping and crimp in a seperate step?

Yes, that will help and try increasing flare. Clean and inspect your seat stem as well.

Also we use the word 'crimp' but don't crimp 9mm. Just press out the flare/bell and stop. The case wall should be straight at the mouth. Over crimping 9mm deforms bullets and can even cause bulged cases in the extreme.
 
Catfish that is exactly how much I crimp, just enough to take the flare out, no more. The rounds I have pulled show at most a very light circle around the bullet, not cutting/damaging the coating. I will definitly clean the stem and increase the flare some. Thank you guys, I know I can always get help on here.
 
@Tatershooter what you described is exactly what happened to me switching from RMR 147 plated to their new FMJ. They work in my Shield 1.0 but not my FS 2.0. I bought an EGW case gauge and the rounds failed.

I later read on here that many people found that the RMR FMJ required a little more crimp. I’ve been too busy with other things that I haven’t gone back to make the changes to my dies.
 
I had read the disclaimer on the RMR site about the 147 FMJ. I also talked to the RMR owner and he was really concerned about the short leade on the CZ’s. I also talked to him and he warned me about CZ's and such. However, I have shot over 1000 of them with only a couple of minor issues and I think that I have resolved that. I also feel (and this does not come from a "MASTER CLASS" reloader....but at least an experienced NOVICE" that the issues are NOT related to the chambers and the RMR warning of SEATING VERY DEEPLY....as in the COAL is minimal. I have pasted (it is LONG) a post that I made on the "What did YOU do in the Reloading Bench" Thread.

Basically, I know from my OWN experiences and experiments that crimping seems to be the most critical area. I would suggest that the OP run an experiment like I did. Shoot a few "OK....they fired" loads in EACH GUN. Retrieve the shells from each gun and segregate them. MARK THEM..... or mark ONE set of 5 or so and not the other set of 5.

THEN, try the once fired in each gun (similar to the plunk test). Remove barrel. Push in lightly on the cases. Do they ALL go to the same depth (measure if you like using calipers and a fixed spot on the barrels to ensure that BOTH seat to about the same depth in each barrel. I think they will....but that is a guess.

THEN....do my experiment. Take 2 or 3 once fired from each lot (marked) and then gently use a pair of needle nose pliers and flare the case. GENTLY and keep doing so until you can seat whatever bullet you were shooting in each one. Leave the bullet sticking out as much as you can.

THEN....push in the cases in one barrel. Pull them out with your finger tips. Measure the overall COAL for each one. NOW....repeat the experiment for the OTHER barrel. That will tell you if there are differences in the chamber and the leades. Repeat usin the OTHER sample of once fired.

I THINK you will find that the COAL is way in excess of anything you would load or try to feed from the magazine. By doing so with the once fired, you eliminate the crimping and you get a really good ideal of the chamber profile.

As to the Lyman Roll (Factory) Crimping die. I know a LOT of folks at our range (club) that have had chambering issues and now use the Lyman die as a crimper ONLY and not a seater. They then use a case gage or do the plunk test and that has supposedly fixed the issue....but they spend a lot more time than most folks do reloading.

My take.....I had battery issues with my CZ. YES, it was a bit tighter, but it did NOT have anything to do with the leade....as RMR stated. It was a matter of OVER CRIMPING. My Glock 17 (less than 1000 rounds) worked flawlessly and ate everything (Remember Mikey from the cereal commercial)....occasionally an issue with my Smith PC 5L....but never my Rugers (LC9S, SR9C and P95). I was crimping way too much. I corrected that (see below) and now have no issues.

Since I wrote the post below, I DID use the method again....but this time I did the precise measurement. Sure enough....using the 3/8 turn or maybe a smidge more, I was spot on. I was exactly 0.004 LESS than the sum of the Bullet ID plus 2X the case wall thickness. SO, it works.

I can also state that I have spent a LOT of time recently talking to a Master Class BE Shooter (one of the top at Camp Perry this summer). He uses a Dillon and runs a tapered crimp. He now has a CZ and is going to help me set up my new XL750. He ONLY uses a case gage (Wilson is where he got it....I think) on his MATCH rounds (9mm and 45). The rest he just bulk bags and takes them to the range and shoots and says that OCCASIONALLY, he will have an issue. He reracks the slide or gives the slide a "forward bump" with the heel of his hand and usually it goes BANG....

This may NOT address the issue....but after blindly crimping based on "Gee I think that is OK" and 2500 rounds later....I now know that I overcrimped...... Have a shot of caffeine and read the post below....IF INTERESTED....

Don’t pretend to be an expert reloader, but I had problems with 9mm and I have seen folks with $3500 Wilson’s complain at the range about feeding and bulging.

Also heard a lot of comments about only using the Lyman factory crimping dies... Going to upgrade to a Dillon XL750 and keep my RCBS dies for short runs or experiments. The Dillon dies are also "straight wall or RING resizing dies" and the crimp is tapered, not rolled or factory.

Also talked to the RMR owner about the 147 FMJ and his “advice” on how NOT to have problems on a CZ chamber which supposedly has a shorter leade. This is what I learned, from several sources and my own experience...or possibly inexperience.

I used once fired shells and barely belled then with a pair of needle nose pliers so I could slip in a bullet. I then removed the barrels from a CZ Shadow 2 and a Springfield Armory Range Officer. I had observed that bulging was not an issue in the Glock 17 & 34. It would take anything. Smith Performance Center 9L was a little more finicky. Take a Failure To Fire (which is actually a chambering problem) and put it in the Glocks...BANG. Same For Ruger’s....which I have five 9mm.

Bottom line pushed the shell with the sliding bullet into the SA RO and the RMR 147’s are barely in the shell. Then move the same round to the CZ and it pushes in a little further. BUT that was in the 1.230 COAL range. 1.170 is the max if memory serves me. So the FTF issue is not the short Leade. It is the crimping.

A friend that was a bench rest shooter walked me through the proper crimping setup. I compared that method with how Dillon’s video says to set up a crimped. SAME Process.

I found that I had the crimping die set at least 0.100 to far down. So, the bulge was the issue. This is how I set it up and have not had any issues since then. It also helps to read a little. The heavier or over crimping you do, the greater risk of bulging. RMR says to just seat lower. Yes, that is one fix, but not the correct one. All you are doing is spreading the overcrimping bulge out. Need to adjust the crimp properly. Measuring to me is tricky. You need a high resolution profile comparator to properly do that. Many can accurately measure....but after you read the article, try my method.

https://www.taurusarmed.net/forums/...anation-how-set-right-amount-taper-crimp.html

Ideally, if you extend the ram to the top of the stroke with a belled shell and then screw down the die with your fingers until very snug, then you back off on the shell and screw the die down 1/3 turn, that will work. You are shooting for lowering the die around 0.025....one full turn is 0..070.

But the above also depends on how much you Bell. I think this will also work....maybe even better.

Measure the bullet OD.. Subtract 0.004. That is the ID that you want the shell to be at the lip or leading edge of shell AFTER CRIMPING. Here is what I might suggest as a practical way to get there...

Follow the SAME setup. Use a BELLED shell (sized with no primer). Do the 1/3 turn DOWN. NOW.... Measure the inside diameter of the lip. It should be the same as the Bullet Diameter MINUS 0.004.

Keep adjusting until you the ID of the crimped shell is in that range. NOW you CAN test that. Full length resize say 25 rounds. Bell, but don’t put in a primer. Drop in your bullet (keep the COAL in the recommended range for that bullet). Run the belled shells through the crimping dies with a properly seated bullet. NOW....will these shells fall into the barrel and either fall right out when you invert the barrel? Can you pull out the shell with a Fingernail or is easily removable with your finger tips? If so, then use your fingers and try to TWIST the Bullet. Is it TIGHT? OR put pliers on the case rim and another pair on the bullet. Can you move it or twist it. If the answer is NO and it PASSES the PLUNK TEST in your barrels....then you are probably good to go.

You should notice, if you were overcrimping, a reduction in the press handle force for seat and crimp. If it sticks, then go down about 1/8 turn on the crimping die....remember to adjust the seating plug UP an equal amount to maintain COAL. Repeat using small increments such as 1/8th turn.

If it did NOT stick....then drive on....but if you are worried about TOO much Crimp, STILL, then back out 1/8 of a turn and run some more....then the Plunk Test. Eventually, you will (should) get chambering problems on the PLUNK test....then go down another 1/8 turn.....just to be sure. Do the Pliers or Finger pull/twist test.

You can pull the test bullets resize the shells and use them now. Nothing wasted.

My experience is that once you have the crimp set to a good, practical MINIMUM, then the tapered crimping die will not be bulging the side walls, regardless of bullet length. One man's experience and understanding....others may have issues....but it works for me....
 
ate everything (Remember Mikey from the cereal commercial)...

Mikey hated everything. His friends were amaze when he ate the cereal. I am not sure how Mikey's dietary preferences were turned 180 degrees from what was in the commercial.
 
Mikey hated everything. His friends were amaze when he ate the cereal. I am not sure how Mikey's dietary preferences were turned 180 degrees from what was in the commercial.
Good Point. The Glock DID eat everything. The CZ Shadow 2, which was the most finicky and hated some of my reloads and PURPORTEDLY also hated 147 RMR's unless you seated them very deep.....NOW likes everything I fix....since I quit overcrimping... Thanks for the correction....
 
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