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what makes a bullet tumble?

8K views 27 replies 9 participants last post by  Bindi2 
#1 ·
I had some bullets tumble at 100 m from my no 4 today - what would make this occur?

thanks
 
#3 ·
Not Quite Tumbling

BB-
I saw some ultrahighspeed film of an artillery shell leaving the muzzle of a howitzer a long time ago, maybe I can describe what happened----

As more and more of the shell's bearing surface left the barrel, the tip of the spinning shell started to rotate around the line of trajectory. When it finally popped out, there was quite a bit of rotating yaw at the tip of the shell and very little at the base. The shell at that point was describing a spiral course around the line of trajectory.

So a crown defect, of whatever kind, which allows the bearing surface to come free on one side before the other, which allows gas to escape past the bullet unevenly, is going to make this wobble worse. Maybe bad enough that the wobble never stops at all.

Then there's whatever a two-groove barrel does to boat tail bullets---wobbling bullets are a classic feature of this combination.
Personally, I think some of the two groove barrels give a little tic to the boat tail just as the bearing surface leaves the barrel---but I can't prove it.
-----krinko
 
#4 ·
In addition to what Bindi2 stated, worn barrels and worn crown/muzzle will cause bullet tumble, with boat tail bullets making it even worse. Flat base bullets when fired in a worn barrel tend to expand and fill the bore and a boat tail bullet does not expand as well to fill the bore. If the crown is worn and has gas leakage, the escaping gas can push on the boat tail and destabilize it making it yaw and tumble.
 
#5 ·
Military projectiles show lead at the base this allows the pressure to open the base of the projectile to seal in the barrel. Civve projectiles are flat based copper jackets. Highland 174gn FMJBT are a good copy with a boat tail. This also highlights the shortness of contact area to the barrel. As the barrel wears more expansion of the bullet is required hence the the design used very simple. Talk to your local bullet maker supplies available june july
 
#6 ·
long and the short of it is.....

If your barrel is past its prime...maybe corroded or badly worn....the flat base ones are the ones to go for.... In Oz its hard to beat 170 flat base TAipans.

If your barrel is in 'new' condition then go for the 174 Grain Sierra match kings as being about the best.

Alternatively if you can get 'em just use the 170 grain Taipans for everything and you wont go far wrong.
 
#7 ·
If your barrel is past its prime...maybe corroded or badly worn....the flat base ones are the ones to go for.... In Oz its hard to beat 170 flat base TAipans.

If your barrel is in 'new' condition then go for the 174 Grain Sierra match kings as being about the best.

Alternatively if you can get 'em just use the 170 grain Taipans for everything and you wont go far wrong.
For the Americans reading this and wondering what the hell Whiterider is talking about (Taipan bullets) just buy Hornady 174 grain round nose bullets for your Enfields, they shoot very well in worn barrels. ;)


 
#9 ·
Reddog

Read my lips, I’m American and Whiterider is Australian, Tipan bullets are sold in Australia and Hornady bullets are made and sold in the USA.

P.S. Drink more coffee.

P.P.S. Whiterider and I are retired and have nothing better to do than give each other a hard time.


 
#12 ·
I've had some really outstanding

results with the 174 Grain Sierra Matchkings in a No.1 Mk 111 target rifle with a brand new Lithgow Heavy barrel. Groups that you had to look at a few times to believe. The load was Canadian military cases ( 1942) with 41 grains of 2208 (Varget) and CCI primers. Loaded to 'magazine' length.

On one occasion I got 5 shots into slightly under 2 inches from the bench at 200 yards. That rifle is so good I put it away against the day when I can no longer see the 'military' sights and have to go the girly way and use Central sights.... :)

Hopefully that day is a long long long way off...... :) So yeah, the quality of the 174 Grain boat tail Sierra Matchking is right up there.

There is also a guy here in Victoria (Bruce Bertram) who makes custom bullets and cases for all sorts of weird calibers. He also makes a 168 grain open point 303 projectile. Havent done a lot of testing on it yet, seems ok so far at least up to 300 yards) but its freely available (from him) and he does a lot of exporting to the USA.

And no, I have no links to him or his company, didnt marry his daughter or look fondly at his wife...etc etc usual disclaimer.
 
#14 ·
Tight

results with the 174 Grain Sierra Matchkings in a No.1 Mk 111 target rifle with a brand new Lithgow Heavy barrel. Groups that you had to look at a few times to believe. The load was Canadian military cases ( 1942) with 41 grains of 2208 (Varget) and CCI primers. Loaded to 'magazine' length.

On one occasion I got 5 shots into slightly under 2 inches from the bench at 200 yards. That rifle is so good I put it away against the day when I can no longer see the 'military' sights and have to go the girly way and use Central sights.... :)

Hopefully that day is a long long long way off...... :) So yeah, the quality of the 174 Grain boat tail Sierra Matchking is right up there.

There is also a guy here in Victoria (Bruce Bertram) who makes custom bullets and cases for all sorts of weird calibers. He also makes a 168 grain open point 303 projectile. Havent done a lot of testing on it yet, seems ok so far at least up to 300 yards) but its freely available (from him) and he does a lot of exporting to the USA.

And no, I have no links to him or his company, didnt marry his daughter or look fondly at his wife...etc etc usual disclaimer.
barrels;) and boat tails a very good combo other wise back to the military style when accuracy drops off and hey presto good as new. I also have a feeling that a smaller chamber in the mix has an effect as well. I have a #4T with a tighter chamber than any thing else :D
 
#13 ·
Mr Ed HORTON. You buy our lithgows we buy your Savages and LBs. I see by the last auction over here somebody scored a LB#4mk1*T with a Lyman Alaskan scope. But then i hear somebody has a Pratt and Whitney stamped Lithgow in the USA o well what goes around comes around i will keep looking.
 
#24 ·
yes Reddog....

Edward Horton;334577 Drink more coffee [QUOTE said:
You are right on. I blew through the words in the post after being mesmorized by that splendid 5 shot group which I assume was shot offhand.

Edward shot that group offhand at 200 yards, one handed, in a howling gale while holding Skennertons book in the other hand....and all the time making rude remarks about Australian coachwood forends exploding......
 
#18 ·
Yeah, we'll I have a nice 1917 Lithgow, and it's staying right here in the US!

Let me translate, "Well, mate, Ahv gut a 1917 Lithy 'n she's stain rot hare in th' Unotted Stets!"
 
#19 ·
Seriously,

For dynamic stabilization, here's a very good link;
http://anarchangel.blogspot.com/2007/01/stabilization-mythology.html

You can also refer the Kneubuehl's work on ballistics (gyroscopic stabilization of a bullet), but this is scientific stuff and might be hard to follow if you are not a fan of Isaaac Newton.

In short, he shows that too-long-for-twist-rate (whatever the weight of it) bullets will not going to be stabilized so it will thumble.
There is also the way the weight is distributed in the bullet (whatever it's rarely seen, especially with modern hot bonding core to the jacket of the bullet - but rarelly happen with "compound core bullets" i.e. steel-lead) but this can occur if you have an "overbore" barrel and a very long leade, because this can cause the engraving of the rifling to be uneven (To know if this is the cause, try to find a spent bullet, look at it carefully, you will find that the grooves on the bullet are longer on one side this it is on the other).
 
#20 ·
I ain’t shooting no stinking Commie Pinko Chinese bullets that got lost in Australia in MY Enfield, I don’t care what that old, old, old, old Australian pilot has to say.


A tai-pan was an influential foreign businessman doing business in China or Hong Kong in the 19th century. The Chinese term is now used in a more general sense for business executives of any origin. The Chinese term literally means big class which is equivalent to the English term big shot.

Go ahead Whiterider, “hit me” ! :rolleyes:

 
#22 ·
The point of the projectile rotating around the line of trajectory is called nutation.
Mr. Sukey

Your posting is one of the reasons why the Australians think we need to eat Vegemite, they think all Americans have poor eyesight.

Please look at the forth posting down in this thread and think about eating more carrots, you are suffering from poor eye nutrition
(not to be confused with nutation)



 
#26 ·
Don't worry, Bindi2

Our Gvt can be as stupid as yours... might be a Commonwealth brainworm (surely some kind of neurocysticercosis - first sign is a will for a complete ban of firearms)and just give away our jewels...
Take good care of them, these oldies need exercise and a good diet.
'Sure it likes Kangaroo and Dingo meat... maybe even rabbit... 'cos they're now said to be too old for two legged games....
 
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