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9mm Bullet Tumble.


Macinaw

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I am using Summers Enterprises 124gn poly coated lead bullets wit 4 grns of Red Dot.  The bullets sometimes tumble (hit the paper sideways).  I was told that Red Dot is a "fast" powder that is not allowing the bullet to engage the rifling of the barrel causing the bullet to tumble.  I was told to switch powder to Tight Group.  Will TG be a slower burning powder that will solve the tumbling issue?  Thanks for any help!

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99% of the time bullet tumbling is caused by undersized bullets rattling down the barrel and exiting unstabilized. This could be caused by a number of things. I would check the diameter of the bullets you are using against slugging the bore to find its diameter. Over crimping is also one of the main causes of unstabilized bullets. If your bullet checks out, if your bore is not over sized I would look at the amount of crimp being applied. Red Dot has nothing to do with this. Changing powder types is most likely not the answer.

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Was the load developed in/for the revolver?

 

I have/had a favorite 140 grain lead bullet load for my M&P 9MM.  Shot pretty good.  Moved from the M&P to the CZ pistols and those loads tumbled like crazy in the CZ's.  Every one of them (P09, CZ 85, two or three CZ 75's).  I just kept shooting them till all of them were used up (I think).  I never did slug a barrel on the CZ's.

 

I loaded up some of the same bullets (have a few boxes of them) with a different powder at a charge weight that increased the velocity and saw no tumbling.  Groups are nothing to brag about, but the bullets didn't tumble at the higher velocity.  Have you tried (if you can for that powder) increasing the velocity?

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Bullet hardness will also have some bearing on the issue.  A harder bullet is less likely to obturate, especially with low pressure loads.

 

Main thing is to have the bullet .002 larger than the bore diameter.  Also no crimp, just straighten the case walls to remove the belling.

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Overall length of the loaded cartridge can also be a big factor.  If the bullet has too long of a jump before it engages the rifling, it can cause problems.   I've solved tumbling problems just by increasing cartridge length to near the maximum that the chamber will accommodate.

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2 hours ago, Macinaw said:

I am over crimping.  

 

You actually "crimp" bullets only for revolvers ...

 

For semi-autos, you simply remove the bell that enabled you to seat the bullet.

 

Your case should be straight up and down when you finish "crimping" ...  :) 

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In my .40 limited guns I had to run a .400 bullet in a barrel I had that was TIN coated.  These same bullets will tumble in a new gun with a schuman hybrid, I have to run .401 bullets or they will tumble.  Some bullet companies will send you some raw lead bullets, that are softer, that you can use to swage your barrel with to determine the size you need.  The crimp can also be an issue, but so is bullet to barrel fit. 

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I was fascinated with the accuracy issues that plague the 9mm and played around with this a few years ago by slugging  barrels, chasing powder, different weight bullets and COAL. I finally looked at what the AMU uses. When I started using 115g bullets at 1150 fps, all my accuracy issues went away .

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8 minutes ago, 72stick said:

I was fascinated with the accuracy issues that plague the 9mm and played around with this a few years ago by slugging  barrels, chasing powder, different weight bullets and COAL. I finally looked at what the AMU uses. When I started using 115g bullets at 1150 fps, all my accuracy issues went away .

Interesting response.  

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On 3/22/2018 at 8:41 PM, Macinaw said:

I was told that Red Dot is a "fast" powder that is not allowing the bullet to engage the rifling of the barrel causing the bullet to tumble. 

 

As others have said, this is nonsense.  Tumbling is typically poor bullet to barrel fit or damage to the bullet, OR the bullet simply not moving fast enough to remain gyrostabilized all the way to the target, with this last option almost certainly not the case (just possible).  

What is your crimp measurement?  Take one of your loaded cartridges and measure right at the case mouth, and measure with the thin, bladed tips of the calipers, not the wider part further into the jaws.  The 9mm case is tapered, so if you center the thick part of the jaws over the case mouth, you're actually taking a measurement behind the casemouth.  Use the thin bladed tips right at the case mouth.   There are a number of different ways to determine the "proper" case mouth diameter for a particular bullet, but you can use .379 for every bullet you load for 9mm and be fine.

Also, what is the measured diameter of the bullet?

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I disagree with the no crimp for semi autos idea.  With no crimp I  get bullet setback.  If I lightly crimp so there is an indentation in poly and plated bullets, I get no setback and have no problems.

 

My bullseye buddies who shoot 9mm for the Center Fire leg tell me they have to drive the bullets fast to get acceptable accuracy.

 

Dardas Bullets sells soft lead balls for slugging your bore.  They will even measure them for you if you send them back.

Edited by zzt
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Nothing wrong with a small amount of taper crimp or circumferential crimp like from a Lee FCD.  My experience is that coated and plated, and lead bullets for that matter, are more sensitive to "issues" related to crimp.  It may be possible that simply changing to a jacketed bullet you may be fine.  I usually pull a couple of bullets looking for excess crimp and make a couple of dummy rounds that I chamber repeatedly to see if they lengthen.

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5 hours ago, zzt said:

 With no crimp I  get bullet setback.  

 

If it feeds, and is accurate, there is now problem.

 

Lots of times, a little crimp in a semi-auto will cause

either malfunctions or inaccuracy, or both   :) 

 

You shouldn't need "crimp" to solve bullet setback - that's

a matter of neck tension, which can be addressed with

an undersized sizing die - then you don't need a "crimp".

Edited by Hi-Power Jack
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Crimping past flush with a straight-wall or tapered case like 9mm designed for a taper crimp can actually reduce neck tension and make the matter worse.  As you bend the metal at the case mouth inward, the case walls below it want to bow out in response.  They don't visibly bow out, but tension is reduced as they  try to.  Just flush is what you want.

I would recommend never using a Lee FCD on lead bullets.  It will swage the bullet shank and can lead to tumbling.  I should have asked that already.  If you are perchance using a Lee FCD with these bullets, that's likely part of your problem.  Use a regular taper crimp die and crimp to flush, not past.

 

Edited by IDescribe
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Crimp is a misnomer. It should properly be called de-bell. Only only bell from the powder thru die to seat the bullet, and only enough de-bell to case gage. Crimp does not hold bullets in place, that is neck tension (interference fit between the bullet OD and the case ID). Notice there is almost no perceptible crimp on my 357SIG Major loads, which has the shortest neck tension of all semi autos.

 

image37742.jpg

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