What is slump ?

[Harter66]

I recently learned that I have no clue what "slump" is.

I had this stupid idea that it had something to do with the nose section of the bullet changing shape under acceleration with incorrect alloys or too long a nose . Also that if it should happen in a not symmetrical fashion your bullet is ruined for consistently striking the same point each shot.

So is slump not the bullet sagging into a different shape than what was chambered?

[tazman]

I recently learned that I have no clue what "slump" is.

I had this stupid idea that it had something to do with the nose section of the bullet changing shape under acceleration with incorrect alloys or too long a nose . Also that if it should happen in a not symmetrical fashion your bullet is ruined for consistently striking the same point each shot.

So is slump not the bullet sagging into a different shape than what was chambered?

There are 2 versions of slump that I am familiar with(there may be others). One of them is exactly what you described. The other is when you are heat treating cast boolits in an oven in order to harden them and you get them too hot and they begin to melt/soften.

[Le Loup Solitaire]

One of the definitions of "slump" was/is when the bullets tilts off its axis while still in the bore (of a rifle) when the force applied is too much. The example given by Col. Harrison in his discussion on the performance of cast bullets in 30 cal was the Lyman #311413 in 30/06 when driven too fast. His idea was that the relatively short ogive did not provide adequate support. Another factor that would definitely contribute to the slumping would be the nose of a bullet being too undersize and this too would also reflect lack of proper support. A bullet that slumped or was tilted off axis would shoot wild when it exited the bore, sometimes seen as "keyholing". LLS

[vzerone]

Harter, I apologize for being abrupt with you on the bullet slump. I'm going to explain and although I couldn't find a fired bullet I drew up what the bullet would look like under various stages of slump. First I will explain it. Let's imagine a flatbase spitzer point cast bullet. It would have full bearing bands, but the spitzer nose is by no means a bore rider as it kind of just sets in the center of the bore not touching the land tops. Now when the alloy is too hard for the pressure you hit it with, or put another way, if you don't hit it with enough pressure its exits the barrel looking pretty much like you loaded except for the rifling engraving and being swaged down in the bore/groove some. That is the first picture at the top that I drew. Next when you hit with more pressure that is able to try to compress the alloy, we know that you really can't compress metal so the pressure pushing very hard on that base causes the metal to move forward in the bullet because the bore/groove walls prevent it from expanding more then their diameter. The moved metal then starts to move into the ogive portion of the bullet that doesn't have contact with the bore/groove and in turn making more bearing surface because it pushes the metal outward too. In turn the sharp spitzer nose becomes less pointed. That's the second picture down. If you hit it with even more pressure all the same above happens except the pushed forward metal pushes out even more of the spitzer nose and it becomes even less pointed. That's the last bottom picture. The bullet through all the phases still retains it's point at the tip, it's just that the ogive changes much. Now the picture to the right of those other three is what many describe incorrectly as nose slump. That never ever occurs in real life. Also what doesn't occur is your description of a pointed nose becoming a roundnose. It would take an acceleration that is beyond small arms capabilities. You're talking about an exceptionally high velocity. You know as objects approach the speed of light they also become shorter according to Einstein and other scientist. I would like to see that high speed photo of the bullet you said that happen too.

This is also posted in the HV thread.

What Le Loup Solitaire posted the word slump would not be a good description. Tilted as he mentioned is much better. Slump would be more when bullet drooped or bend.

http://i1318.photobucket.com/albums/t643/vincentz1/img076_zpshjvrqmz2.jpg

[country gent]

Slump is basically thee deformation of the bullet other than impacts. A bullet can slump when a mould is opened to soon and it too hot to maintain its integrety, these some times look bent or oval. WHen heat treating to high a temp may cause alloy to soften and fall. A loose fitting nose of to soft an alloy may deform under pressure not filling the bore evenly. This is ussually caused by heat or pressure. Lead can flow and do funny things under pressure or with heat close to melting temps at the point it softens and starts to lose integrety.

[vzerone]

Slump is basically thee deformation of the bullet other than impacts. A bullet can slump when a mould is opened to soon and it too hot to maintain its integrety, these some times look bent or oval. WHen heat treating to high a temp may cause alloy to soften and fall. A loose fitting nose of to soft an alloy may deform under pressure not filling the bore evenly. This is ussually caused by heat or pressure. Lead can flow and do funny things under pressure or with heat close to melting temps at the point it softens and starts to lose integrety.

It's obturation I like to say.