Interesting bullet cross section

[RJW NZ]

Just found one of my old photos of a bullet I cut in half; its interesting to see just how much aluminum is at the front of the bullet and holding the lead very much to the rear and making that rearward center of gravity the ol 303 is known for.

The other standout feature is the varying wall thickness on each side of the lead, no wonder there's all sorts of discussion about varying quality of war time ammo, and the corkscrew flight this feature will cause when the rifling gets it going at 174,000 rpm.

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[paulseamus]

RJW

Very interesting. Perhaps during a war quantity is sometimes more important that quality.

What is the age of the cut projectile? Is it WW1 or WW2?

Have you compared with a modern projectile such as a Sierra Match 174g?

If not let me know and i will get the hacksaw out.

Paul

[RJW NZ]

What is the age of the cut projectile? Is it WW1 or WW2?

Have you compared with a modern projectile such as a Sierra Match 174g?

Hi Paul, the ammo was ww2 brit, and no I haven't compared many at all. I did have one which had something like compressed cotton in the tip where the aluminum is on this one. The other ww2 bullet I wanted to open but don't currently have are the ones that appear to have a 1/16th or less hole in the tip. It might be formed if the copper jacket is rolled somehow or it may be something which has a function, as creepy as those implications might be, such as increased wounding capacity.
That varying jacket thickness is kind of stunning. I have a whole dissertion here by someone discussing that exact thing and the repercussions on accuracy, but with the caveat that 'this kind of thing is rarely seen', lol, except in the very first one I open.

If you're going to go along I'll find a couple more to pen up as well. I got about a dozen different profiles, wartime and civilian use, we could look at.

[hopmanhenk]

this is a picture I made of some sixties surplus bullets (AI marked, dutch)


left is copper clad steel
center is copper
right is whitish clad copper

[TonyE]

I think you will find that the side of the envelope that appears thickest is the side that you started cutting and the hacksaw blade has dragged some of the softer copper envelope into the lead. If you polished the cut I think you would find the variance in envelope thickness would disappear. I have sectioned many .303 bullets of all types and even wartime production is not that bad.

The Mark VII bulets with the "cotton" material in the tip is a wartime economy that used compressed wood fibre to save aluminium. Other materials that have been used as a tip filler over the years are ceramic, compressed paper and plastic. U.S. contract production of .303 ball ammunition for Britain did not have the lighter tip filler and so the bullets are slightly shorter than the regular Mark VII.

Your other point is about WW2 hollow point bullets. There were none in WW2. Are you thinking of the Mark IV and V round nosed hollow point bullets which date from the late 1890s? These were banned by the St.Peterberg Convention and were relegated to training after 1899, although some were issued in 1905 for an expedition to Somaliland. There is no aluminium tip in those and the hole is punched into the bullet about .3 inches deep, the piece of envelope cut out being carried to the base of the hole.

The WW2 early production .303 Incendiary B Mark VIz bullet had a very small hole (less than 1mm) in the nose that was filled with solder, but it is virtually invisible unless one is looking for it, so I doubt if you mean that.

Regards
TonyE

[RobD]

Hi Tony
hollow point .303 were used in a limited way in the early engagements of the Boer War (British troops), and extensively in the Bambata Rebellion of 1906 (South African troops).
Rob

[villiers]

Could the "corkscrew effect" (mentioned above) be the reason why my No 5 shoots better at 300 metres than at 100?

[RJW NZ]

Could the "corkscrew effect" (mentioned above) be the reason why my No 5 shoots better at 300 metres than at 100?

thank you, lol, I once got in trouble for suggesting such a thing. I have some text on this, I'll see what I can locate.

[Bruce_in_Oz]

The "corkscrew" effect is called "precession"

It affects all bullets to some degree. A perfectly made bullet, perfectly centred in perfectly concentric rifling, in a perfectly crowned barrel that exhibits no twisting or vibration during firing, will give the least precession.

If you spin a bullet on its axis, in a vacuum, at 200,000 rpm, it will rotate around an axis aligned with the centre of mass.

Try the same thing in air and any external inconsistencies will come into play.

Then project this spinning bullet forward at, say, 2,500 feet per second. This will add air pressure and turbulence drag to the picture.

Add a gravitationally appropriate downwards acceleration of 32 fps sqd.

Quietly ignore the fact that the earth is rotating.

We are not operating in a perfect world. Bullets are not perfectly concentric. Barrels are not perfectly concentric. Barrels whip and vibrate under the stresses of guiding and containing a bullet going from a standing start to 2500 fps in two feet of travel.

Then when this less than perfect object starts traveling through the air and falling under gravity at the same time, it gets really interesting.

Gravity, forward inertia, rotational inertia and air resistance are in play from instant the bullet leaves the muzzle. And then there is great potential for the bullet to be disturbed to some degree by uneven gas flow around its base as it exits the muzzle.


The "corkscrew" effect (precession) is a result of all these little imperfections at launch. A "good" bullet launched less than perfectly will settle down under the influence of gyroscopic force. However, if the spin rate is too low, it will not be able to compensate for air resistance and it will "tumble"

On the other hand, if the bullet is spun too fast, either it may break up early in flight, or the gyroscopic effect will cause problems down range. A correctly spun bullet is, in fact constantly "wobbling" slightly because the trajectory is NOT a straight line. The faster the spin of a "good" bullet, the closer to the original line of departure it will try to go. In the absence of gravity, this is not a problem. However, because the bullet is actually falling from the moment of departure, the trajectory is a curve, a parabola, more or less. If a bullet were fired in a gravity field but with no atmosphere, it would stay on the line of departure all the way to the target. and it would strike the target at that angle; not exactly point-first.

However, here on Earth, we got the whole set, so, the bullet must be spun fast enough to overcome lateral deflection by the air, but not so stable that it does not allow the air resistance to act to keep the nose-tail axis closely (but never perfectly) aligned with the parabolic trajectory. A well stabilized bullet will make a tiny adjustment of its alignment at each revolution. Spin it too fast and it will still make the adjustments but further apart and in potentially much larger steps. Another important factor is the location of the centre of mass, fore and aft. Move it too the rear significantly and the bullet MUST be spun faster to reduce any tendency for lateral rotation around the absolute centre of mass. (See Mk7 .303 and 5.56 NATO SS109 for starters.)

The trick is that at short ranges, many bullets may be still trying to achieve a balance of forces, but will settle down ("go to sleep" as some older range shooters described it) Another interesting problem is that the rotational velocity is almost unaffected by air resistance. However, forward sped drops continuously after launch. The "steps" between corrections get closer together as the rate of change of direction on the parabola increases: very convenient.

[RJW NZ]

Thanks BruceinOz, really interesting and a good explanation I could follow too, cheers