How fast is too fast?

[puffnstuff]

G'day,

Just one for fun. A few gag cartridges were posted on the forum a while ago like 50BMG's necked down to .17 and that sort of thing.

Some of the serious comments were around it being useless because the bullet would be going too fast.

What actually is "too fast" though? Is there a particular velocity?

What actually goes wrong?

[Chronos]

One thing that can happen is as muzzle velocity increases so does the revolutions per minute inserted on the billet by the rifling in the barrel, suddenly a bullet designed for 40,000rpm is spinning at 60,000rpm and it throws its jacket off and flies apart.

Sometimes happens in a fast twist .223 barrel, say 1:8" twist when someone shoots thin jacketed target 50gr bullets designed for a 1:12" twist barrel.

Really the main reason something like that 17-50 cal won't work is that there's no way of burning all that powder before the bullets left the barrel and you just end up with a blowtorch that destroys the bore of the rifle in a couple of shots.

Chronos

Edit: Just out of interest a look at actual numbers provided by another member here show actual rpm of bullets would be closer to the 200,000-300,000rpm mark. Pretty hard to imagine the forces at work here.

[bunnybuster]

Too fast is when you load a 40gr hornet projectile in a 22-250 at about 4100 fps and it flies apart about 10mtrs downrange,

bloody hard to shoot a group,

Be Safe,BB.

[Westy]

Too fast is when you load a 40gr hornet projectile in a 22-250 at about 4100 fps and it flies apart about 10mtrs downrange,

bloody hard to shoot a group,

Be Safe,BB.

But it makes shooting Clays with a hornet easier!!!!!!

[handofcod]

I've heard of some rapid expansion projectiles hitting bone at too high velocity and disintergrating on impact rather than penetrating. Not sure what velocity is required for it to do that. Over 3000fps?

[1290]

There have been countless experiments at attaining the greatest velocity, I believe it was POA who was trying for 5000fps but couldnt quite get there, it seems the velocity is limited by the deflagration of smokeless powder... I normally use a velocity of 1585metres per second (=5200 feet per second) which may appear to be a limiting factor on bullet velocity...

As far as rotation; that is the issue with superfast bullet disintegrating (as opposed to the linear velocity -
a 7" Twist 22cal at 3000fps is spinning at 308,500 rpm
a 10" twist 30cal at 3300fps at just under 240,000 rpm...

the math for bullet rpm at muzzle:
(feet per second and twist in inch per rotation)
( Vel x 720 ) / Twist
eg ( 3000 x 720 ) / 10 = 216,000 revolutions per minute

[headspace]

Too fast is when you load a 40gr hornet projectile in a 22-250 at about 4100 fps and it flies apart about 10mtrs downrange,

bloody hard to shoot a group,

Be Safe,BB.

Move the target closer, call it a pattern instead of a group.

[nords]

Just out of interest a look at actual numbers provided by another member here show actual rpm of bullets would be closer to the 200,000-300,000rpm mark. Pretty hard to imagine the forces at work here.

Sooooo more than the gravitron ride at Wonderland?

[fordj]

I've heard of some rapid expansion projectiles hitting bone at too high velocity and disintergrating on impact rather than penetrating. Not sure what velocity is required for it to do that. Over 3000fps?

I dunno exact numbers for velocities, I've read the same except in these cases it was people using hollow points and match bullets instead of projectiles designed for hunting.

Shooters fault for using the wrong thing more than the bullet not performing.

[puffnstuff]

Really the main reason something like that 17-50 cal won't work is that there's no way of burning all that powder before the bullets left the barrel and you just end up with a blowtorch that destroys the bore of the rifle in a couple of shots.

Must be like a hurricane behind the bullet too and probably would blow it all over the place?

[SendIt]

Pasted from another thread here...

As you know, a bullet typically move in an arc.

To shoot at distance your rifle barrel is actually pointed up fractionally and the bullet goes out and upwards tip first, then levels out, then descends tip down - Like the arc of throwing a javelin.

If you're shooting at super velocities, the problem can occur that the tip of the bullet doesn't come down and the line of the bullet doesn't follow the arc. The bullet still moves in an arc, but it's at an angle so the tip is always higher than the bottom. It just sails forward at that upward angle.

One this wrecks your accuracy, and two when the bullet hits it doesn't penetrate cleanly as intended and tumbled into the target causing inconsistent results.

[bunnybuster]

Pasted from another thread here...

This is where you cough into your hand at the same time saying bulls**t,for a variety of reasons you lot can figure out yourselves,

Be Safe,BB.

[rainwalker]

I'm picturing a football moving through the air for that... Makes sense to me?

Spell out the reasons for a newbie BB?

[jackles]

Didn't the US army do that on purpose for a bit for tumbling damage on targets?

Shooting 5.56 nato a bit too fast?

[1290]

Pasted from another thread here...

This is where you cough into your hand at the same time saying bulls**t,for a variety of reasons you lot can figure out yourselves,

Be Safe,BB.

Not entirely bulldung, the description is though....
To put it in the simplest terms, A projectile doesnt always travel with its centreline parallel with the direction of travel. That is with the line of the trajectory (arc) coinciding with the centreline... There are many forces at work and concepts involved, stability, gyroscopic stability, drag, centre of mass, centre of pressure.....

[WesleySnipes]

Didn't the US army do that on purpose for a bit for tumbling damage on targets?

Shooting 5.56 nato a bit too fast?

I believe this was mostly unintentional. From memory the M16A1 made its debut on the battlefield during the Vietnam war, so it suffered from some teething problems.

The original rate of twist was 1:14 which was too slow to stabilise the bullet causing the rear end to tumble over the front when hitting flesh, effectively ripping some limbs off due to the erratic and somewhat unpredictable behaviour of the bullet.

They cured this in later versions by quickening the twist rate and upping the the bullet weight by 2 grains to 57g which is what stopped the tumbling problem.

They also raised the sight offset to around 3 inches because they noticed due to the heat and humidity paired with the materials the rifle was made of and it's semi automatic low recoil capabilities, under sustained fire you would get a lot of heat rising of the barrel and creating a mirage effect distorting the targets.

Again all this is from memory, so if the particulars are incorrect then feel free to correct me.

And because the Russians and the north Viets were observing this massive damage, the Russians developed the AK74 (5.45x39) which replaced the older 7.62x39 AK47. This is also influential on the move by all nations to start adopting smaller diameter and faster moving projectiles.

[jackles]

I believe this was mostly unintentional. From memory the M16A1 made its debut on the battlefield during the Vietnam war, so it suffered from some teething problems.

Yeah I've read a bit about the M16's and their early days.

Sounds like a bit of a disaster from many accounts.

[Old Fart]

Prone to jamming if I remember rightly.

Quite the problem during a war.

[1290]

I recall the issue was related to cleaning, advised to clean less frequently than necessary(if at all!), hence the jamming issue (and the forward assist)

Wrong powder or something with the first M16s....

[Yelp]

Did some googling on the jamming

The first issues of the rifle generated considerable controversy because the gun suffered from a jamming flaw known as “failure to extract,” which meant that a spent cartridge case remained lodged in the chamber after a bullet was fired.

According to a congressional report, the jamming was caused primarily by a change in gunpowder that was done without adequate testing and reflected a decision for which the safety of soldiers was a secondary consideration, away from what the designer specified, as well as telling troops the rifle was 'self cleaning' and at times failing to issue cleaning kits.

Due to the issue, reports of soldiers being wounded were directly linked to the M16, which many soldiers felt was unreliable compared to its precursor, the M14, which used stick powder, varying from the M16's utilization of ball powder.

[Norton]

as well as telling troops the rifle was 'self cleaning' and at times failing to issue cleaning kits.

lmao, yeah righto then.