How much obturation?

[Protrucker]

obturation

I love that word. I think I'll try and use it in a sentance today. :hmm: :winking:

:nono: There's nothing in the defination about changing shape. I think people should look up the meaning of a word before they try to use it:

Main Entry: ob·tu·ra·tion
Pronunciation: "äb-ty&-'rA-sh&n, -t&-
Function: noun
Etymology: Latin obturation-, obturatio, from obturare to obstruct
Date: 1610
: OBSTRUCTION, CLOSURE
- ob·tu·rate /'äb-ty&-"rAt, -t&-/ transitive verb

Pronunciation Key

© 2001 by Merriam-Webster, Incorporated

 

[jtmattison]

obturation

I love that word. I think I'll try and use it in a sentance today. :hmm: :winking:

:nono: There's nothing in the defination about changing shape. I think people should look up the meaning of a word before they try to use it:

Main Entry: ob·tu·ra·tion
Pronunciation: "äb-ty&-'rA-sh&n, -t&-
Function: noun
Etymology: Latin obturation-, obturatio, from obturare to obstruct
Date: 1610
: OBSTRUCTION, CLOSURE
- ob·tu·rate /'äb-ty&-"rAt, -t&-/ transitive verb

Pronunciation Key

© 2001 by Merriam-Webster, Incorporated

Technically speaking, the ball is an obstruction in the bore. That's the whole concept of a firearm. The gasses from the burning powder charge are just propelling it out of the bore. Without the tight fitting "obstruction" you wouldn't get the bang and the fast flying ball. All you would get is a poof!

HD

 

[robinghewitt]

I never fired a Whitworth but I'll bet if you shoot a hexagon out of it you'll still get a round hole. :hmm: :grin:

Well, if you load a round suppository in a Whitworth you get a hexagonal hole in the target.

I don't want to get in to the science of this because I've been there before and it's a complete waste of typing, but here's a clue...

To deform a ball/bullet you have to squeeze it.

The powder pushes on one side, if you can figure out what pushes on the other side you'll understand why suppositories obturate and balls don't.

I'll give you a clue, it ain't the air :thumbsup:

 

[rabbit03]

Again I think your premise is wrong in that round balls and bullets have totally different physics working when on top of an explosion in a barrel.
One obvious difference is that a roundball has a slight bearing surface in which to engage the rifling. Conversely a bullet has much more bearing surface, and is usually alot heavier in the given caliber. A heavier projectile with a cylindrical shape is more apt to not want to move when acted upon by the explosion under it. Therefore it is more likely that it will expand into the rifling whereas a round ball which is much lighter and with much less bearing surface will not.

rabbit03

 

[rabbit03]

Hey Robin your right of course. I had a Whitworth and used the lyman rounded sides bullet in it (didnt want to pay for the hex mold) and guess what vuala! A hex bullet was recovered from the berm. Amen.

rabbit03

 

If you're referring to my post methinks you better go back and re-read what I wrote. The physics aren't different, nor did I imply that they were. One is merely a heavier projectile than the other thus the upsetting will be greater.

On a bullet, the nose of the bullet is providing the resistance for increased expansion over a round ball,(there ya go squire). roundballs example from the Lyman book, (I've read that thing lots also), of their double balled load is a differnt example of nearly the same thing. The rear starts moving before the[url] front....sumpin[/url]'s gotta give. Same thing with a single round ball only on a lesser scale.

Given the squire's post saying a cylindrical bullet comes out of the hex bore of the Whitworth hexagonal in shape oughta say something about the upsetting of a projectile. Roundballs upset to some degree whether anyone wants to believe it or not. Rifling won't show on them, (I agreed with that in my first post), as the patch is there and the ball never comes into contact with the rifling., it can't show. As squire said....too much wasted typing. Deal me out.

Vic

 

[rabbit03]

OK

rabbit03

 

[robinghewitt]

If you load a suppository shaped bullet in a barrel that is so short that the bullet actually projects half way out of it, the bullet goes mushroom shaped. It's been done, can't remember where I saw the photo :hmm:

Obturation happens at the bottom end of the ML barrel where the pressure and acceleration is greatest.

I think round balls will deform but they will go slightly egg shaped with litle increase in diameter :thumbsup:

 

[robinghewitt]

Correct :thumbsup:

It pushes against the inertia of the bullet. The hard idea to grasp is that if you apply thousands of pounds of accelerating force to a bullet, the bullet must push back with thousands of pounds of inertia.

It doesn't seem reasonable, but everything has to be equal and opposite :grin:

A ball has most of its mass on the centre line of the bore and very little where it touches the bore.

 

[Mike Brooks]

Yea, OK,....I'm following......but, does it make a difference if the moon is full or not? :blah:

 

[Walker357]

Only to her, not to me! :grin:

 

[marwat06]

Correct :thumbsup:

It pushes against the inertia of the bullet. The hard idea to grasp is that if you apply thousands of pounds of accelerating force to a bullet, the bullet must push back with thousands of pounds of inertia.

It doesn't seem reasonable, but everything has to be equal and opposite :grin:

A ball has most of its mass on the centre line of the bore and very little where it touches the bore.

:cursing: I knew I should have paid attention in my Freshman Physics Class

 

[RedFeather]

I had an 1879 rolling block and sold it to a fellow who complained that the leade was too big in the chamber. Had to explain to him that this was intentional, especially in a military balck powder cartridge gun, due to heavy fouling. Had to have a generous chamber in order to physically stick in more than one or two rounds during combat. Can't shoot - stop - wipe. The "oversize" chamber works perfectly fine with soft lead bullets as they obturate (obdurate?) sufficiently to form a good seal. Not like modern guns. I would guess a RB obdurates some, but doesn't have the same intertia, as mentioned above, to create much upset.

 

[robinghewitt]

Yea, OK,....I'm following......but, does it make a difference if the moon is full or not? :blah:

I did say it was a complete waste of typing :shake: