What If Powder Didn't Push The Boolit? Leading?

[emrah]

So I'm throwing out another question into the "What do gas checks REALLY do?" controversy.

I've read all six pages of the "The Real Story Behind Gas Checks" sticky/thread and there are certainly many more theories and explanations/beliefs than I'd thought possible!

Now, I was more on board with the theory that a gas check protects the edges of the boolit where hot gases can blast away (melt) and re-deposit (solder) the lead in the bore. But I never understood WHY a boolit traveling (for example) at 1400 fps will not lead, but all of a sudden, when you up the charge and push it to 1500 or 1600 fps it will magically start to lead. I don't get it.

Even at the lower velocity, there is STILL a lot of hot gas and pressure. Not as much as a higher powder charge (and resultant higher velocity), but there STILL is a lot of pressure and heat. Certainly (in my mind) enough to melt the edges of an unprotected boolit.

So here's my question: What if there were NO hot gases? What if we were to somehow accelerate the boolit to and past the typical "leading threshold"? I know it's theoretical, but let's say you COULD push the boolit with air, a ram, magic, whatever. Just no hot gases so they are completely out of the equation.

What do you think will happen? Would we still get leading due to pushing a boolit too hard due to boolit "skidding"? Would we get leading at the "normal" threshold for a typical powder/boolit/velocity combination?

I don't know how anyone could test this, but it would certainly solve at least ONE of the questions regarding barrel leading: whether or not the hot gas affects it. Any thoughts?

Emrah

[Sonnypie]

Well, you may as well accept the fact that an explosion of hot gases does currently push the bullet out.
So have a beer and cool your imagination down.

One day we will have finger mounted rail guns, point and bink! :groner:

But we aren't there yet, Buck Rogers.

[emrah]

Yeah, wouldn't it be nice if someone developed a clear plastic tube as a barrel? You could fire the gun and slow-mo the boolit as it heads down the bore. Understanding of ballistics would take a quantum leap. Until then, my biggest project is making my own gas check maker.

Emrah

[btroj]

I have gotten lead buildup in my Lee push thru sizer. Sizing a .436 bullet to .432 without any lube can do that. No hot gasses involved.

Even with a see thru barrel and hi speed camers it would be hard to know what is happening. So much of what we need to,know happens at an almost microscopic level. We need to know what happens at the interface between barrel, bullet, line, and pressure. How do they interact? Does the lube get pressurized?

In time we may be able to develop computer models that help pur understanding but that takes time, money, and knowledge. Not sure who is going to undertake that when there is no viable financial reason to do so.

[tjones]

Computer models have given us weather predictions that are worthless, and ice caps disappearing on Mars, Earth too. How bout good ole experimenting for answers.
tj

[Sonnypie]

Computer models have given us weather predictions that are worthless, and ice caps disappearing on Mars, Earth too. How bout good ole experimenting for answers.
tj

Oh no!
Now you threw truth, logic, and common sense in there!
Emrah is doomed!
Ahh, to be a kid again.

(Is Emrah some cartoon caricature?) :popcorn:

[Dthunter]

I hate to inform you, but it "IS" compressed air that creates the mechanical means to facilitate a bullets movement down the bore.

Leading can be caused by factors we know of and dont. I know that lead(reguardless of alloy) has a yield point. This requires a physical force applied by gas pressure, friction,or heat. Leading can be caused by all, or a combination of these.

A metals ability to resist these forces can also be affected by the speed(velocity) at which the force is applied.
As far as heat from the combusting powder charge, I think is very "minimal". Not enough time to really heat things up. Remember, a person can pass there hand through a flame quickly and barely feel the warmth of the flame.

The laws of Thermodynamics state: Energy can niether be created, nor destroyed.
But, energy can be converted from one form to another. Such as the forces of the expanding gasses being converted into the motion of the boolet, or the detruction of the boolet material/alloy.

I believe that the velocity/speed of the combustion causes the "majority" of the issues.
A faster load (with a given powder/boolet combo) means a higher pressure load. If that pressure is applied too fast for the boolet alloy to be able to adequately respond by its movement. If the boolet doesnt move sufficiently before the alloy exceeds it elastic limit, something else has
to "yield". This can cause a leading issue through boolet deformation. The boolet would go well past the desireable "obturation" point.

Slower powders apply thier peak pressures later in the firing sequence. The boolet gets a slower/gentler start, allowing the forces of enertia to be less extream (during initial accelleration) on the boolet alloy. The boolet can therefore be pushed to a higher velocity before another load factor starts to fail. Of course you need adequate barrel length, and case capacity to take advantage of this.

Friction due to a lack/inadequate lubrication can cause leading.

Bore condition can cause it.

Many, many things can cause leading.


Cast boolet shooting is all about experimenting with various components to arrive at a desired performance level.