Do you believe that lead boolits actually obturate (swell up) when fired? Yes or No

[Russel Nash]

Bullshop also wrote:

Your obviously a smart fellow so why don't you get this?

Do I detect a little bit of snarkiness there too?

[high standard 40]

Sounds like a troll to me. Classic. I've seen them on other boards. It's how they get their kicks. The smart thing to do is not argue with him.

[Heavy lead]

This is somewhat of a confusing thread, but obturation does happen IF it needs to IF the projectile is soft enough to respond to the pressure it is being pushed by whether it be in an air rifle or a 65,000 psi Weatherby magnum with a Barnes Triple Shock, simple as that.
Maybe I'm splitting hair's here with the definition, but would not obturation be the action of a bullet being pinched down by a tight spot in the barrel and then opening back up to fill the lands and grooves as it traveled throught the bigger part of the barrel as well?
Also wouldn't the definition of obturation also include a bullet or boolit taking on different land and groove pitches as it traveled through a gain twist rifled barrel as well?

[357maximum]

Do you believe that lead boolits actually obturate (swell up) when fired? Yes or No


I do not believe it....I know it.

Why ask a question ...PM me and invite to join the discussion and then argue anything that is posted that goes against the grain of the state your brain? now that there is a real question. A discussion is pointless when one side fails to discuss things....at that point it is an argument....and is what I think you truly wanted.

You seem to have YOUR closed mind made up otherwise, and I do not feel like argueing common sense observations with you......so I will leave it at YES.

[missionary5155]

Good evening
If solids are not compressable.. How is it that atomic matter compressed to reach crtical state ? I realise an EXPLOSION is used but compression is compression.
Pure lead (1-40) must do something when Smacked in the rear by Blackpowder otherwise my borewidth nose riding boolits would not have rifling engraved on those noses.
Happy New Year everyone.

[Marlin Hunter]

How can a boolit not obturate with 50,000 pounds pressure applied to the base?

The same thing happens when a bug hits your windshield at 65mph. It obturates all over the windshield.

[Old Caster]

I recently saw an article in a magazine where large lead bullets were fired out of different length rifle barrels (down to two inches) and it had pictures of what the bullets looked like when they were leaving the barrel and it was stunning how much fatter the bullets looked in the back than in the front. It was maybe double size. I don't remember for sure what magazine it was but I think I gave it to one of the guys in my pellet league and will ask next Thursday about it and will post if I find it. I picked it up at the range in the free magazine section so it is likely that it was at least a few years old. I believe it was a BPCR magazine.

[softpoint]

Somewhere I have a chart that I got off of a cast bullet site that has the pressure required to "upset" bullets of different alloys. I believe the article states that the optimum load for a cast bullet is one that meets the pressure required to "upset" the bullet out of a particular alloy, but not so much in excess of that that the lube fails, and leading starts, or the bullet is accelerated so fast it "skips" over the rifling. Now, I can't see what goes on inside my barrel, but some things would indicate this is true. One is that you can minimize or eliminate leading by using a slower burning powder to achieve a given velocity. Light loads with fast burning powder, on the other hand, lead for the opposite reason, I have seen a hard cast .44 caliber bullet lead badly in a .44 magnum with only 6 grains of Unique. Leading might stop at 10 grains, or be less. But as you try to get higher velocity ,leading will come back again, unless you go to a slower burning powder, such as 2400. Now, individual guns can vary widely how they respond, but most shooters here at this site have observed this. Isn't this due to obturation, or lack of it? My guess is that it is.

[montana_charlie]

for the sake and sanity of scientific discussion let's NOT use the word compress when it comes to talking about a solid like a lead boolit.

Would you accept a term like 'swage"?

Swaging happens rather slowly compared to the firing of a cartridge.
But, the pressure exerted by a powder charge is easily equal to the pressure developed by a swaging press.

The swaging die has an internal 'shape' as does a barrel have one.
Under pressure the lead exactly fills the swaging die, as a bullet fills a barrel.
Because the swaging die is closed on the end opposite from the ram, the action can occur slowly.
Because the action happens so fast, the same reforming of the lead takes place in a barrel that has an open end.
With swaging, the lead is 'held back' against the pressure of the ram by the closed end of the die.
In a barrel the lead is 'held back' against the pressure wave by enertia.

Obturation happens, Russel. You may as well accept it.
You won't accept the action of a minnie ball, and I understand why you don't think that is adequate proof.

But, if obturation did not occur, the Maxi-Ball couldn't work...and it doesn't depend on a hollow base.
It is a bullet that starts out at slightly less than bore diameter, and is bumped up to groove diameter when fired.

If something is making you doubt that obturation is possible, that may be from using hard alloys with smokeless powder.
Hard alloys don't bump as easily, and smokeless doesn't bump very much, sometimes.

CM

[Bullshop]

Please define snarkiness. I am not sure what it means. If it means a person loosing patience with someone that refuses to accept the truth after the truth has been repeatedly offered by multiple persons then yes I have become snarky.
If it means a person loosing patience with someone after that someone has been repeatedly proven wrong and the person in the wrong trying to hide the fact by accusing those offering the truth of wrong doing then yes again I am a snarker, possibly a mega magnum master of snarkology.
Maybe before I go any farther with all that it could mean you should give me the real meaning. I may be totally off base and it could mean something like a person so knowledgeable about that of which they speak that they virtually know everything there is to know about it. If so thank you very much !!! Very observant and nice of you to say so.
God Bless
BIC/BS

[lwknight]

Russel, The body of the group has a well founded opinion from experience,trial and error and logic , and you are not going to change it. You are outnumbered 10 to 1 at least (discounting those on the fence)
If you want to be a sucessful heretic you will have to do your experiments in silence and publish the r sults with sufficiently recorded details to sell the unpopular idea to anyone.

[waksupi]

Gentlemen, keep the tone polite, please.

[jhrosier]

Wish I had the pics I saw years ago but I can't even remember where they were published. ....

F.W.Mann,The Bullet's Flight From Powder to Target, 1909

Jack

[Bullshop]

We just looked up snarky. Our dictionary said it means to be testy or irritable.
OK OK I am guilty.
But hay you come on up here and live with little daylight and temps in the -30's and see if you don't get snarky.
You think I am snarky this time of year man you best not get into it with BS Mom.
Please forgive my snarkiness. I will try to do better.
Blessings
BIC/BS

[405]

Marlin Hunter wrote:



And that my friends is what brought me to start a poll here.

From my high school and college physics/chemistry classes, there are only four states of matter:

1. gases
2. liquids
3. solids
4. plasma

Also, in those classes, I learned that of the first 3, only the gases are compressible. Liquids are not compressible, and that explains why hydraulic pistons work on something like a crane or a back-hoe. And why they don't use pneumatic rams or pistons for some stuff. Solids aren't compressible, like a block of steel. So my thoughts are that a cylindrical piece of lead is a solid, and therefore can't compress or be compressible. Unless of course it was surrounded all around by something strong like a steel swaging die and pressed into a particular shape.

What I am saying is that with the exception of very soft lead and/or Minie balls, I think lead boolit obturation might just be a myth.

Sounding more and more like a "bait and troll" excercise. Not all that long ago the greatest minds in the world had trouble coming to grips with the concept of kinetic energy. Much later (a couple or three hundred years later) and really fairly recently the same genre of scientific minds had trouble dealing with the relationship between kinetic energy and the impact physics of a high velocity, low mass object. An even simpler concept is obturation as it pertains to the discussion here. The lead bullet, a plastic body.

[454PB]

I had to vote no.

They can only obturate if one of the critical measurements isn't correct.

OK, this is about the line of discussion I expected. Boolits can't obturate if there is no room to "bump up".

Now, as a test let's use a section of rifled barrel as a sizing die. It's groove diameter is .451". I now drop a .452" boolit into it's "mouth" then place the die center punch on the boolit base, and proceed to pound on it with a 3 pound ballpeen hammer. When it exits the die, what will in measure?

What if you place the die on a steel plate and continue to pound on the center punch? Will it bump up?

Sure, if this same .452" boolit is fitted in a cartridge case and a chamber that is oversized, it will bump up some as it enters the cylinder throat, to be immediately sized back down as it enter the barrel. But if the chamber and throat is properly sized, it won't allow it to bump up, the same as the example above.

So.....can they obturate? Yes, if they are undersized to start with. Do they obturate? Not necessarily.

[Marlin Hunter]

But hay you come on up here and live with little daylight and temps in the -30's and see if you don't get snarky.

BIC/BS

I'll trade you 5 million liberal commies for your -30's and little daylight.

[geargnasher]

Russel, would you please give us your own exact definition of "Obturate"?

I just want to make sure that we don't have confusion about it here because many people use it to mean "bump-up" or "enlarge" when actually I understand it do refer ONLY to the state of SEAL achieved, by whatever means, at any point of boolit/barrel interface.

Boolits don't obturate to fit the bore. Obturation is what happens when a bullet seals the gases in the bore.

Thus, it should be said that "obturation of expanding gases from the powder combustion is achieved in the bore by the boolit's ability to conform/bump-up/enlarge/swage/flow/etc."

We had a pretty long and heated thread about this awhile back, I think it boiled down to a simple matter of rhetoric.

If I'm wrong in my definition, someone please correct me.

BTW, I voted affirmative because obturation occurs in all my guns that don't have gas-cutting and resulting leading. I thank JimInPHX for his extensive development of the mulch trap and examination of many of my own fired boolits to determine that not only do bullets tend to swell to fit a bore (if they are undersized and soft enough) but the noses can slump like crazy if launched too hard and the alloy too weak and nose unsupported.

.357 Maximum said it best: I dont' believe it, I know it. This ain't a religion, faith has nothing to do with it.
Gear

[Marlin Hunter]

OK, this is about the line of discussion I expected. Boolits can't obturate if there is no room to "bump up".



So.....can they obturate? Yes, if they are undersized to start with. Do they obturate? Not necessarily.

They will always obturate, although you might not be able to measure it. Take 0.001 inch and keep cutting it in half. When you get to 0 (zero) let me know. Even if the boolit only expands 0.00000000000000000000000001 inch, it still expands. The barrel is also trying to expand (get bigger), between the breech and the boolit, from the same expanding gases that are pushing the boolit forward. Then you also have the barrel trying to stretch because the gases are pushing the breech back, and the boolit is pushing the front of the barrel forward. And you also have the boolit trying to rotate the barrel at the same time the barrel is trying to rotate the boolit. 3 things happening at the same time with the barrel: it's moving all over the place. Thing of a drunk, retarded pimp trying to walk.

[Bullshop Junior]

The answer is yes, and that is all there is to it.