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Old August 30, 2010, 12:07 PM   #1
Field
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Bullets tumbling in flight: Causes

I had this load cooked up that i used:

Rainier 124g Plated RN
4.4g Titegroup
1.135 col

Apart from being pretty innaccurate i had a number of these bullets going sideways and tumbling out at 15 and 25 yards.

I was wondering what causes there would be for a bullet to tumble, i was thinking that with these plated bullets the velocity was too high and some of the bullet was coming apart while exiting the barrel? That is my best guess.

What other factors would cause a bullet to tumble?
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Old August 30, 2010, 12:12 PM   #2
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Rifle, pistol, revolver, caliber, barrel length, barrel twist rate, there are a few details missing here. Like for instance doe this mystery gun in the mystery caliber shoot other loads well?

Curious minds want to know.
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Old August 30, 2010, 01:02 PM   #3
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Wrong diameter bullet! Wrong bullet for your barrel's twist rate! Too low of a velocity!

Need to have more info as per above!
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Old August 30, 2010, 01:33 PM   #4
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Yes, we do need more detail.

Another suspect would be a copy-paper target without a proper backer. Sometimes low velocity bullets will tear the paper leaving holes that appear to be from bullets hitting sideways even though they didn't. Try shooting at a piece of cardboard to verify the bullets are indeed tumbling.
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Old August 30, 2010, 01:57 PM   #5
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And also too much pressure. Plated bullets are supposed to use soft lead bullet loads. You're 10% over Hodgdon's Tightgroup maximum (4.0 grains) for that bullet weight with lead. Most soft bullets have a nominal pressure you don't want to exceed, and it often is below maximum. I would back off to 3.6 grains and work up, looking for best accuracy.

If the bullet is long enough, try seating it out to headspace on the bullet (back end of case head flush with back end of barrel when you drop a round into the barrel to use it as a gauge). Provided that doesn't make the finished cartridge too long to fit in the magazine and to feed properly, that usually improves accuracy and reduces fouling with soft bullets because it stops them from entering the throat at an angle. Pressure is not increased significantly by firing soft pistol bullets this way.

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Old August 30, 2010, 02:11 PM   #6
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Sounds like the load is actually too hot for the bullet, rather than too mild.

Ah, I see Unclenick beat me to it.


More information is definitely needed. We are all even making an assumption about the cartridge in question. Need info!

Pistol?
Cartridge?
Barrel length?
Velocity?
....
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Old August 30, 2010, 02:15 PM   #7
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Too hot a load & excessive crimp. Plated bullets will flake the plating off if the crimp is too tight
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Old August 30, 2010, 09:15 PM   #8
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Quote:
Pistol?
Cartridge?
Barrel length?
Velocity?
Pistol: Springfield XDm
Cartridge: 9mm
Barrel Length: 4.5 inches with 1:10 twist

Velocity:

((approximately)) 1100fps probably a bit more than 1100fps. I havent chrono'd this particular load with this bullet but other bullets with the same powder charge were in this area.

also look at this thread i made for more info if you want:

http://thefiringline.com/forums/show...00#post4214400
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Old August 30, 2010, 09:24 PM   #9
chris in va
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Ah yes, tumbling. I just spent a year trying to get my lead bullets to fly straight.

First it was my 9mm going in sideways with my CZ and HiPoint carbine. Tried various weights and designs, only to have the same problem, especially with hotter loads. All were .356".

Then I ran across a few knowledgeable guys that told me FIT IS KING with the 9mm, and I switched to a 38 Special mold sized to .358. Buckshot patterns suddenly went to measurable groups.

Ditto for the 45acp, except in that case my gun didn't like the tumble lube design and I switched to a 'normal' lube groove type measuring .002 over bore diameter.

I generally have better success with milder charges, so in your case I'd probably knock things down toward the lighter end of things. According to my Lyman manual, a 125gr JHP has 3.8-4.2gr of Titegroup. The 120gr LRN is 3.2-3.8. I'd definitely say you're playing with +P pressures there.
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Old August 30, 2010, 09:26 PM   #10
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Quote:
Pistol: Springfield XDm
Cartridge: 9mm
Barrel Length: 4.5 inches with 1:10 twist

Velocity:

((approximately)) 1100fps probably a bit more than 1100fps. I havent chrono'd this particular load with this bullet but other bullets with the same powder charge were in this area.


I would definitely place a wager on bullet-to-bore fit, and being pushed too fast.

Back it off to 900 to 950 fps, and let us know what happens.
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Old August 30, 2010, 11:16 PM   #11
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Quote:
Back it off to 900 to 950 fps, and let us know what happens
in IPSC and IDPA shooting the minimum power factor for 9mm is 125k.

Power factor is calculated by bullet weight x bullet velocity

950x124=117.8k

this doesnt even meet minimum PF. I am wanting a PF in the 136k range for good margin of error. I prefer 124g bullets to be going AT LEAST 1075fps.


I think i should probably just switch to Montana Gold bullets.
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Old August 31, 2010, 07:58 AM   #12
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My first guess was he was shooting a Marlin. :barf:
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Old August 31, 2010, 09:30 AM   #13
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Given your parameters, that was definitely the wrong bullet for the job.
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Old August 31, 2010, 04:52 PM   #14
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Given your parameters, that was definitely the wrong bullet for the job.
Yep.

Never ask a standard lead bullet to do a jacketed bullet's job. (I don't care if they're plated. They're still lead, and can't be pushed as hard as jacketed stuff.)
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Old August 31, 2010, 05:41 PM   #15
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"Then I ran across a few knowledgeable guys that told me FIT IS KING with the 9mm, "

Fit is king in every cartridge/firearm combo. Firesufficently undersized bullets and they tumble. Fire soft bullets too fast and they will strip undersize and then tumble.

Chris, I suspect if you increased the diameter of your tumble lubed bullets by 2 thou they will also shoot fine.
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Old September 1, 2010, 02:08 AM   #16
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Quote:
I'd definitely say you're playing with +P pressures there.
well i used another load with Remmington 124g round nose bullets for a number of matches with 4.5g of TG that were pushing those rounds about 1150fps or 142PF this being one example:

http://www.youtube.com/watch?v=Ow_QcjnA8WY
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