Idle thought, overloaded pressure velocities?

[44 AMP]

Some comments in other threads got me thinking, so, I'm asking...

For those of you who use the computer load calculation programs (I don't)...

If you screwed up royally, and used a fast pistol powder in a rifle load, creating dangerous pressure (up to a blow up)...

What velocity would the bullet get?

(looking for a calculated answer, I have no intention of doing a field test)

 

[Will-j]

Not as high as one would hope for/expect, if any as any pressure high enough to blow up the rifle/pistol would probably be expended on the destruction of the action/chamber and not to pushing the bullet down the barrel.

Just an unprofessional guess.

WILL

 

[44 AMP]

as any pressure high enough to blow up the rifle/pistol would probably be expended on the destruction of the action/chamber and not to pushing the bullet down the barrel.

The bullet is the most easily moved part of the system. Unless something is physically stopping it (like another bullet in the bore), a high presser load will push the bullet out. Logic says that if the action (actually the case, first) ruptures, while the bullet is in the bore, the pressure will vent and the pressure driving the bullet will go away.

BUT, there is the matter of the exact moment when this happens (in a blow up), and depending on how much velocity the bullet has BEFORE the action lets go, might still be enough to clear the barrel.

Lets look at another situation, that of drastic overpressure, SHORT of an action failure.

Let's say the handloader screws up, and in a .308 loads with 2400 instead of rifle powder. I know of a case where this happened. The action did not let go, but the case did. The bullet absolutely cleared the bore, at some speed.

Based on the pressure signs on the case, the load generated 90-110,000psi. The rifle was damaged, minor parts broken by venting gas, but was repaired and returned to service.

What I'm wondering is, what estimated velocity would the bullet have in a case like this? Essentially double normal pressure. I would expect a higher (but not double) velocity. Can the computer loading programs calculate this?

 

[jason75979]

The bullet is the most easily moved part of the system. Unless something is physically stopping it (like another bullet in the bore), a high presser load will push the bullet out. Logic says that if the action (actually the case, first) ruptures, while the bullet is in the bore, the pressure will vent and the pressure driving the bullet will go away.

BUT, there is the matter of the exact moment when this happens (in a blow up), and depending on how much velocity the bullet has BEFORE the action lets go, might still be enough to clear the barrel.

Lets look at another situation, that of drastic overpressure, SHORT of an action failure.

Let's say the handloader screws up, and in a .308 loads with 2400 instead of rifle powder. I know of a case where this happened. The action did not let go, but the case did. The bullet absolutely cleared the bore, at some speed.

Based on the pressure signs on the case, the load generated 90-110,000psi. The rifle was damaged, minor parts broken by venting gas, but was repaired and returned to service.

What I'm wondering is, what estimated velocity would the bullet have in a case like this? Essentially double normal pressure. I would expect a higher (but not double) velocity. Can the computer loading programs calculate this?

Stand by, I'll see.

 

[jason75979]

Here is a .308win using Quickloads.
Bullet Hornady sst interlock.
The first pic would be a "normal" load with IMR 4064.
The second is using the same amount of 2400. Approximately 122,000psi! And, 3120fps at the muzzle.

 

[F. Guffey]

A north Texas smith was asked to open a bolt on a rifle that shot a 308 W round. The rifle was a 25/06. First reaction, I'll bet that bullet was 3" long when it left the barrel. Problem: There is absolutely nothing that can be said that would change the mind of a shooter/reloader with that kind of reaction.

I know of three barrels that are scattered from Alaska to Houston with FT. Worth in-between, all with muzzles that look like smoke stacks from an old river boat. The one in Houston was created when the shooter failed to remove a bore sight.

F. Guffey

 

[44 AMP]

Thank you Jason!

This is what I was wondering about. We have long known that there is a point of diminishing returns with gunpowder. Big magnums burning 10-15% more powder yet yielding only 5% more velocity, etc.

Rounding off, I see the program says a 100% increase in pressure gives roughly a 25% increase in velocity.

Thank you for running that, it gives me enough food for thought for a while.

 

[FlyFish]

These discussions of pressure vs. velocity often fail to recognize that "pressure" in terms of a kaboom refers to peak pressure, i.e., the highest point on the pressure curve, but "pressure" as it relates to MV is not simply the peak pressure. What accelerates the bullet is not (entirely) the peak pressure, but the integrated area under the pressure curve. The issue is not so much one of reaching a point of diminishing returns but rather the shape of the pressure curve and how it relates to the peak of that curve. A faster-burning powder can generate a higher peak pressure than a slower powder in a particular cartridge yet not result in higher velocities. A casual examination of a reloading manual that shows both pressure and velocity for various loads will show this to be the case. This relationship between peak pressure and area under the pressure curve is also the reason why certain powders are/are not appropriate for certain cartridges.

 

[F. Guffey]

These discussions of pressure vs. velocity often fail to recognize

Then there is the bullet, it must get out of the way, if it does not?

kaboom

I am the fan of the running start, I want my bullets to have that 'jump start'.

F, Guffey

 

[Overkill777]

These discussions of pressure vs. velocity often fail to recognize that "pressure" in terms of a kaboom refers to peak pressure, i.e., the highest point on the pressure curve, but "pressure" as it relates to MV is not simply the peak pressure. What accelerates the bullet is not (entirely) the peak pressure, but the integrated area under the pressure curve. The issue is not so much one of reaching a point of diminishing returns but rather the shape of the pressure curve and how it relates to the peak of that curve. A faster-burning powder can generate a higher peak pressure than a slower powder in a particular cartridge yet not result in higher velocities. A casual examination of a reloading manual that shows both pressure and velocity for various loads will show this to be the case. This relationship between peak pressure and area under the pressure curve is also the reason why certain powders are/are not appropriate for certain cartridges.

I found this post to be extremely enlightening. Thanks flyfish.

 

[F. Guffey]

These discussions of pressure vs. velocity often fail to recognize that "pressure" in terms of a kaboom refers to peak pressure, i.e.,

I am always looking for 'kabooms' that happen at off peak pressure. And am always wondering why there is never an effort to correlate the pressure on a gage with the pressure effect on a case. I have cases that would suggest I have been involved in some risky stuff. Flash holes too large to measure with my flash hole gage. Primer pockets that only allow the primer to touch on one side of the pocket. Then there are the case heads, I have case heads that are so upset the case will not fit a shell holder, I have case heads that will fit a shell holder if I use a small hammer. Then there is the thickness of the case head from the bottom of the cup to the case head, crushed.

F. Guffey