Why does an improperly seated ball cause blown barrels?

[scythefwd]

I got to thinking, I know very dangerous, and it doesn't make sense. BP is shooting a "compressed" load, but barely. The ball/ projectile is to be seated on the powder. But why does one that isn't blow up the barrel? With more room to expand, and the same force required to overcome inerta and move the ball down the barrel, what causes the damage to the barrel? Is it that the ball is biting into the lands where it normally wouldn't be (which would create more inerta to overcome and therefore higher pressures)? I would expect this to be the case with heavier loads (more powder, the futher down the barrel the ball is stared, possibly in full contact with the lands) as well and they don't seem to have the same disasterous effects that an improperly seated ball does. I keep seeing testamonies stating that it took 4-5 "magnum" loads with bore sized projectiles to blow the barrel. This would indicate that the rifle took several overrated loads to work that far up to the blown barrel.

Anyone want to school a beginner on the anatomy of a muzzle loader shot? I would love the details like

(center fire rifle)
1. Hammer strikes primer
2. Primmer bends over anvil
3. Priming compound detonates
4. Detonation goes through the priming hole in the head.
5. Primer is blown back against the bolt face and out of the pocket.
6. Powder ignition.
7. Case expands outwards and backwards to the face of the bolt (reseating primer) / projectile starts moving down the barrel.
8. Pressure peaks
9. Projectile leaves barrel, initating recoil (debated as to recoil starting here or at step 7)
10. Pressure reaches equlibrium with atmosphere.


Who's got some knowledge for me??
Thanks in advance

 

[Oyeboten]

As far as I understand it, if I do, a Metallic Cartridge Case expands and lengthens slightly while not neessarily able to move back, owing to how it's sides are pressing against the Chamber very tightly...or, a Case might or might not move back untill after the Bullet has left the Barrel.


I think the issue with BP Loadings, is that imprudent Air Space, allows the combusting Powder to reach a peak pressure prior to the projectile being in motion, or prior to it being in an appropriate stage of acceleration...where, the duration of the peak is then longer, and undulating or elastic...where, a well seated projectile, the pressure rises in a fair steady way, as the projectile is accelerating.


Smokeless Cartridge Arms anticipate this unhappy Air Space and less than ideal pressure schedule/duration, and undulation, as a normal compromise their Metalurgy is calculated to tolerate, or, depending on the charateristics of the Powder in a given loading, anyway.


Possibly, a naive analogue would be...if one is giving another Car a push with one's own Car...it's nicest if one stars out Bumper-to-Bumper, and one can floor it even, with a smooth progress...

Where starting out several feet behind them, and flooring it, makes for a sharper and rebounding mete...

 

[messerist]

Ditto. I think you hit the nail on the head Oy! God I love this site!

 

[scythefwd]

Oy, you are correct, it stretches backwards. Sorry if my post lead anyone to think the casing moves back, it just lengthens. Thanks for the info.

BTW.. Smokeless guns pretty much rely on this space. There aren't many compressed loads in smokeless because the can do the whole explode your barrel thing. A compressed smokeless powder will burn more slowly until it gets enough air to really burn. At that time, you can have too much powder burning, spiking your pressure way beyond the safe limits. The air gap is contained by the bullet and the chamber, which can be much thicker steel than the rest of the barrel though in the case of smokeless.

messerist,
This is exactly why I keep coming back to this site.

 

[alsaqr]

Blown barrels were a big problem way back when they were thin and/or made of iron. With the Civil War era rifled muskets, failure to seat the heavy Minie' bullet over the powder would most likely cause a burst barrel. Sometimes those barrels burst with properly seated bullets. No doubt modern steel barrels muzzleloder barrels burst when the bullet is not seated on the powder although I can find scant evidence of this on the internet.

Over the years I have recovered hundreds of conical Minie' type bullets from Civil War battlefields and old firing ranges. Quite a few of these bullets have deep marks that were made by the ramrod. Some of those very deep marks could have only have gotten there when the soldier pounded on the end of the ramrod with something heavy.

Every year I remove saboted bullets from the barrels of several inline muzzleloaders. I remove the breech plug, remove all the powder, dump in 10 grains of Pyrodex and fire the gun.

This study was undertaken in about 1890.

http://www.theopenrange.net/forum/index.php?topic=2098.0

 

[RyanM]

BTW.. Smokeless guns pretty much rely on this space. There aren't many compressed loads in smokeless because the can do the whole explode your barrel thing.

Incorrect. What smokeless (or more accurately, cartridge) guns rely on is the distance from the bullet to the rifling. A maximum power rifle load with fast-burning powder, and the bullet jammed right into the rifling, is a recipe for disaster no matter how much air space you have inside the case.

It's that gap between the bullet and the rifling, not the bullet and the powder, which allows a cartridge-fired bullet to get a "running start" before the powder reaches full pressure.

You have no choice about whether the bullet is rammed into the rifling with a non-revolver muzzleloader, so the air space (or lack thereof) becomes crucial.

 

[Oyeboten]

http://www.theopenrange.net/forum/in...p?topic=2098.0


Interesting..!


Hmmmmm....

 

[rcmodel]

A compressed smokeless powder will burn more slowly until it gets enough air to really burn.

Where exactly is it getting this air from?
The bore & chamber are plugged and no air can possibly get in.

What actually happens is all powder contains it's own oxidizer. It makes it's own oxygen as it burns.

Smokeless powder compressed loads are no more dangerous, and pressure is no higher then uncompressed loads, if you are using the correct powder & charge weight.

The answer to the OP question is bullet friction.
If it is setting on top of the black powder charge, it has time to overcome bore friction and accelerate before peak pressure is reached.

If the ball is 6" up the barrel, the powder burn is nearly complete before the ball has time to overcome friction and get out of the way.

rc