9mm HP OAL issue

[BBQJOE]

74413

This is from a 356-125 Lee mold that Erik did. Sized to .357
It weighs in at 115.
Lyman's suggestion for a similar bullet in JHP is 1.09 for OAL.
Firearm is newer M&P 9.
1.09 doesn't want to plunk at all. I went down incrementally until I got a perfect plunk at 1.01
I decided to give a few a go. The first couple shot fine, then one round jammed outside of the chamber pointing upwards.
I'm not real comfortable with this round being so short.
On some of the longer ones I tried to plunk, I could get them to go with thumb pressure but there was definite click or pop as it went in, and wasn't coming back out without a little pry of a screw driver.
Is it possible this gun just doesn't approve of this round, or am I missing something?
I have no problems with my 356-124 Lee TL.

[Ben]

What exactly is " Plunk " ?

[Case Stuffer]

Dropping a finished round into the barrel to see if it chambers without extending past the headspacing point or in other words chambers freely.

Some boolits when loaded to recomended OAL fail to chamber freely due to boolit touching the barrel lands. AS OP posted sometimes a round seated short enough to chamber is to short to feed reliably. Years ago I had a Browning HiPower that I had to free bore 0.060 so that I could seat 135 gr. SWC out far enough to be 100% reliable.

[Ben]

Looks like I'm learning,.............. I'd never heard of " plunk " used to describe a round chambering properly.

[luky-dude]

8 years and 5800 post--and havent heard that one--------you talk to much

[BBQJOE]

Looks like I'm learning,.............. I'd never heard of " plunk " used to describe a round chambering properly.
It's a test for semi-autos. With the barrel removed, a round dropped in the chamber that fits correctly, you will hear a nice clean plunk sound. The round should also fall right back out without any help.

[williamwaco]

Ben,

Next time you "plunk test", drop the cartridge into the chamber and listen to the sound it makes.

Note, you must remove the barrel to perform this test.


.

[Ben]

Sorry, looks like I've been talking too much !

[KYShooter73]

I have the same mold, same problem. Mine are at around 1.08. That's on my M&P Pro..... I just use a case guage, no plunk test. As long as they cycle properly by hand, Im good to go. On my moms Springfield xd they lock up tight every time. I'm just going to seat them a bit shorter unless that in itself causes malfunctions.

[dondiego]

Ben - I just read about the "ker-plunk" test yesterday on another thread and I have been lurking here for years...............off and on.

[Ben]

dondiego

You better be careful with remarks like that, you'll get accused of talking too much also.

Ben

[Iron Mike Golf]

On some of the longer ones I tried to plunk, I could get them to go with thumb pressure but there was definite click or pop as it went in, and wasn't coming back out without a little pry of a screw driver.
Is it possible this gun just doesn't approve of this round, or am I missing something?

The "click or pop" going in sounds like the case has begun to collapse when being expanded. I get that with CBC and S&B headstamps. I get a slight ridge just below where the boolit base will end up. Here's what I'd do:

1. Check the COL of the test rounds that "click" in after you get them back out of the chamber. Have they been set back? Any signs that the boolits are hitting the lands?

2. Track headstamps on the clickers. Is it just a particular set of headstamps or does it affect all of them you have?

3. Inspect the clicker rounds. Is there a shiny or burnished ring on the cartridge case? If so, where on the case is it?

I sort out the CBC and S&B brass and set them aside for jacketed rounds.

[KYShooter73]

Good post Jeff. With mine, at the 1.08 depth all of them are touching the lands on the Springfield XD, but not on my M&P Pro. Im able to sort out any case deformation issues with my case guage.

[BBQJOE]

I gotter figured. I needed to think about this some, and go backwards. This is a new bullet for me, using different lube method.
I tried all kinds of things this morning. I found one round that I set at 1.07, and it plunked just fine. Loaded another, and it didn't.
My 9 brass is a major assortment. Turns out the one that plunked was a CBC case, and it's wall measured considerably less than the ones that didn't pass.
But that led me to find the real culprit, which turns out to be a complete oversight on my part.
In wanting to keep the round clean, I sized them, but did a double dip in recluse instead of tumbling. The extra lube on the driving band was adding almost 2 thousands in diameter to the case. I then resized a few bullets, sat them at 1.065 and tada! No more problems. So in summation, it was more of a case diameter problem than a OAL issue.

La la la! Idiot.

So I believe the new program will be cast, double dip, then size. At least until I get all the things together to try pan lubing with Ben's red or something else.
Another day, another lesson. I kinda hope it never ends, else I get bored.

[rsrocket1]

The M&P chamber is very tight and does not like any residual flare on the case mouth. I have to seat my 0.356" sized 356-120-TC's to 1.05" and had to put put a light taper crimp on it to "plunk" 100% of the time in my M&P 9 barrel. The problem with 9mm is that there is so much length variation in range pickups that seating and crimping in one stage is a pain. I've discovered that using my 38/357 FCD to just kiss the top of the case closes the bell and brings the case mouth to 0.379" and does not swage the bullet down any more because I'm not full length resizing with the FCD.

I shoot with a lightly compressed 4.2g Unique and get a very consistent 1080 fps with this load and 100% reliable feed and ejection. I hate to admit it, but I am much more consistently accurate with the 9mm than I am with the 40 S&W. I get dead-on bullseyes with the first few rounds of 40, but then the flinching starts and I start shooting low. With the light 9mm, it's like shooting an airsoft gun. Dead center all day long.

[BBQJOE]

Thanks Mr rocket!!!

[MtGun44]

Two items to set. LOA to keep from engraving the boolit on the rifling is first, but degree of
TC is also critical. TOO MUCH TC is better for reliability compared to too little,
in my experience, and does not cause problems.

I just call it a drop test. Ben does not talk too much, but some newbies have have smart
mouths. When Ben posts, I pay attention.

Bill