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

[AriM]

I had always wondered if the TC Maxi-Ball indeed did bump up like they said. I started out on tests to find if they did. You now the majority of that bullet fits into the bore quite easily and only the front band on the nose engraves. So finally I was able to retrieve some and they did show rifling on all the bearing bands.

Shooting hollow base bullets too fast, or with too much pressure, blows the skirts off them....we know this.

One final thing we've all heard if you're gangster and you shoot someone just ruin the muzzle (or crown) of your barrel, or even saw off the end of the barrel, it you don't want to get rid of the firearm and forensics can't determine if the bullet was fired from such gun. Meaning the last marks on the bullet are from the muzzle, so even if the bore is larger there, there must be some obturation going on in the entire length of the barrel....in other words constant pressure keeping it obturated.

we are essentially on the same page. glad that my points made to Molly (in response to his points made to me) are cogent, and that you were able to follow them. I am no genius. So explaining what I believe to be true can be a little tough to get through (or maybe not).

I think your points made about why semi-auto cases are hotter than a bolt guns (when properly and initially extracted) are very valuable and further prove obturation exists. ESPECIALLY point number 2. You say that you think the cases are hot because of violent extraction and friction. This is proof of obturation. The case mouth expands to fill the chamber (we all know this to be true). The friction of a tight fit, between the chamber and expanded case mouth causes heat under the extraction process. What causes the case mouth to expand? Powder charge and pressure generated by powder charge. What stops it's expansion? The chamber. That is prime evidence of obturation. It is NOT disputable. If it is, it goes against everything believed to be true about case sizing, reloading and fire forming.

Kudos to you for making that remarkable and logical observation.

[303Guy]

... .and 2. heat from friction of being extracted violently from the chamber. It is No 2 that I say causes the most heat.

I would say the frictional heating of the case taking place during firing and not during extraction. The case grips the chamber quite firmly but internal pressure forces it to creap against the chamber walls. Those creap marks are very fomiliar to us. Examine them and on a longer case they can be seen to get shorter toward the neck, where they dissappear. Now thats a huge dose of friction! But the same case is holding the hot and high pressure flame for the entire duration of firing and a lot of heat is going to be transfered to the case. The reason why an auto case is hotter than others is because it is ejected while still hot, thus keeping the chamber cooler. A rapidly operated bolt gun produces way hotter cases than does a slowly operated gun.

But case obturation is due to internal pressure while boolit obturation would be caused by pressure acting on the base which 'attempts' to accellerate the base faster than the nose, causing the body to swell. Barrels also expand under the pressure of firing. This alone could cause the boolit to remain 'tight' in the bore up to the muzzle as the pressure falls and the bore expansion reduces.

But as Molly keeps on stating, it's the 'obturation' of hard alloys that is under question here. We know softer alloys undergo plastic deformation to a lesser or greater degree. Harder alloys cannot deform in the time the pressure is being applied, not plastically, anyway. So, a boolit might obturate elastically without the lube grooves collapsing. Now, all materials can undergo some degree of elastic strain, harder alloys more so than soft lead. Do those boolits 'obturate' elastically or not? Well, yes they do expand radially under the pressure of firing but do they expand enough to 'obturate' the bore? We can actually calculate it! (I use the term 'we' loosely! I've long forgotten the formulae and it's not a simple one. I'm way too lazy to start looking it all up now - it would take me all day).

[StarMetal]

303guy,

Have you ever got a case hot by resizing it fast??? I have.

[AriM]

I would say the frictional heating of the case taking place during firing and not during extraction. The case grips the chamber quite firmly but internal pressure forces it to creap against the chamber walls. Those creap marks are very fomiliar to us. Examine them and on a longer case they can be seen to get shorter toward the neck, where they dissappear. Now thats a huge dose of friction! But the same case is holding the hot and high pressure flame for the entire duration of firing and a lot of heat is going to be transfered to the case. The reason why an auto case is hotter than others is because it is ejected while still hot, thus keeping the chamber cooler. A rapidly operated bolt gun produces way hotter cases than does a slowly operated gun.

But case obturation is due to internal pressure while boolit obturation would be caused by pressure acting on the base which 'attempts' to accellerate the base faster than the nose, causing the body to swell. Barrels also expand under the pressure of firing. This alone could cause the boolit to remain 'tight' in the bore up to the muzzle as the pressure falls and the bore expansion reduces.

But as Molly keeps on stating, it's the 'obturation' of hard alloys that is under question here. We know softer alloys undergo plastic deformation to a lesser or greater degree. Harder alloys cannot deform in the time the pressure is being applied, not plastically, anyway. So, a boolit might obturate elastically without the lube grooves collapsing. Now, all materials can undergo some degree of elastic strain, harder alloys more so than soft lead. Do those boolits 'obturate' elastically or not? Well, yes they do expand radially under the pressure of firing but do they expand enough to 'obturate' the bore? We can actually calculate it! (I use the term 'we' loosely! I've long forgotten the formulae and it's not a simple one. I'm way too lazy to start looking it all up now - it would take me all day).

the formula is BHN x 1422 = appropriate pressure in chamber

or to find the correct BHN for a specific load.....PSI / 1422 = correct BHN

ALL of this info. is available on LASC website and in the Lee Modern Reloading Book (vol. 2).....I don't understand how it can still be an issue?

has everyone read, and understood both those sources??

[303Guy]

Have you ever got a case hot by resizing it fast??? I have.

No, I haven't. Interesting! But thinking about it, it's quite logical. Work is being done on the case and work is heat. It's more than just friction though - there is the work of plastic resizing as well. I suppose firing an 'undersized' case such as would be needed in a self-loader, plastic deformation of the case as it expands would be another source of heating of the case.

I wasn't disputing the frictional heating of cases, just saying the friction takes place mostly during firing. There would surely be more friction during extraction, especially if the case is still expanded against the chamber wall.

[felix]

AirM, the 303Guy is entirely correct. The formula you are referring attempts to calculate where the expansion is destructive, meaning outside of the plastic phase. Most lino type boolits are shot within the plastic phase and they will distort for a short time allowing obturation, but return to normal after all is said and done. ... felix

We have coined the term "tough lead" to indicate a good returning boolit. Decrease the amount of tin in lino (adding significant lead), the toughness of the boolit can go away allowing permanent destruction. Therefore, lesser pressure, or pressure timing, is mandatory to keep the projectile in the plastic stage. ... felix

Increasing the tin content will also make the boolit loose toughness because of the surface tension parameter as discussed earlier. ... felix

[AriM]

AirM, the 303Guy is entirely correct. The formula you are referring attempts to calculate where the expansion is destructive, meaning outside of the plastic phase. Most lino type boolits are shot within the plastic phase and they will distort for a short time allowing obturation, but return to normal after all is said and done. ... felix

We have coined the term "tough lead" to indicate a good returning boolit. Decrease the amount of tin in lino (adding significant lead), the toughness of the boolit can go away allowing permanent destruction. Therefore, lesser pressure, or pressure timing, is mandatory to keep the projectile in the plastic stage. ... felix

Increasing the tin content will also make the boolit loose toughness because of the surface tension parameter as discussed earlier. ... felix

oh of course. I am not disputing that he is correct. I am disputing, how the question of obturation, can even be an on going question at all. i can't see any evidence or conclusive proof that boolits do or do not obturate. I am under the understanding, that the general accepted conclusion (by industry giants) is that boolits do obturate. not just soft ones, but any boolit that is subjected to pressure (of course to a greater or lesser degree, than the CORRECT combination). the issue of rotational obturation is also completely logical and widely accepted. is it not?

I am just curious how a thread on this subject can reach 11 pages. it would seem that this subject has been moot and generally accepted for many decades.

am I missing some massive bit of information, that shows otherwise?

obturation happens from the beginning of the process to the end, correct?

when the boolit leaves the muzzle, it continues to obturate, due to the gasses propelling it. those gasses don't have anywhere to go, other than out the muzzle with the boolit. the boolit does not have enough velocity from the initial blast to continue out of the bore correct? if it did squib loads would be non existent.

again, I am asking questions....not drawing lines in the sand. I want to know how this can be an ongoing issue. the science is complex, and seems to be incomplete. however, the logic and observations and countless stages of trial and error (over many decades) would all point to the conclusion, that obturation is in fact an effect and it happens. even the hardest boolit, will obturate to some degree, with a grossly inadequate load. Mr. Lee dedicates many pages to this very subject in his book. it is the most tested and cohesive explanation I have seen. I just don't see how anyone here can claim that they know something that is so overwhelming, that it invalidates Mr. Lee's perfect explanations of the subject.




I think the question that should be asked, is more along the lines of : "what constitutes obturation, and is it a proper definition (by today's standards)"

if obturation is the bumping of a boolit because of the effects of powder expansion, gas expansion and detonation. then obturation is an effect that continues through most of the boolits travel, to the destination?

it just seems to me that this is a debate about semantics and an incomplete understanding or incomplete definition of the term. we are all spinning it one way or another (pun?), but all understand the same concepts and accept them.

The current definition seems to have a duality to it. it says that obturation is the bumping of the boolit to seal the bore, before the rifling is engaged. it then goes on to say that this is due to the gasses created and pressure created by the charge. it then seems to end there. that is incomplete (IMO), since the gasses deform the boolit through it's entire travel (since no barrel is perfect). it's really a poorly defined word. maybe that is what the debate is about, and not the effect. I notice that Mr. Lee does try to stay away from the word in his text. yet describes the same thing (essentially).

am i totally misunderstanding the term? or is what I am try to articulate not being put forth in a cohesive/cogent manner?

I am curious how the OP (who I know from other forums and off this site) can ask this question. he is a smart guy and I want to know what lead him to create this poll. instead it seems that it's just an ongoing debate, about semantics.

I am really trying to gain some understanding, beyond what I think I already know. I am open to any and all thorough explanations. I have far less experience than most of the people posting here, but trust what I have read from Mr. Lee and a few other "qualified" professionals. Not just because I read it, but because I have followed their advice, and seen the results myself.

[303Guy]

I am just curious how a thread on this subject can reach 11 pages.

That is easy to explain - it's because there are bunch of experienced, intelligent and curious folks who enjoy a good debate, especially when there are new angles and ideas added along the way. It's no so much learning about 'obturation' but rather discovering how much other folks really do know. I like to think I have learned a lot from it all. It's cirtainly taken me along a new path of patched load development by increasing my understanding of what's going on in a bore when a gun is fired.

I have just tested two loads for my Pig Gun; one produces higher chamber pressure but does not disintegrate the patch, so there is insufficient 'obturation' (shotgun powder). The other, with a slower powder (H4227), produces a higher velocity with lower chamber pressure and disintegrates the patch. Is this not along the lines of what you are saying, AriM?

As to why Russel started this thread - he's already told us. He had nothing else to do that evening!

[AriM]

That is easy to explain - it's because there are bunch of experienced, intelligent and curious folks who enjoy a good debate, especially when there are new angles and ideas added along the way. It's no so much learning about 'obturation' but rather discovering how much other folks really do know. I like to think I have learned a lot from it all. It's cirtainly taken me along a new path of patched load development by increasing my understanding of what's going on in a bore when a gun is fired.

I have just tested two loads for my Pig Gun; one produces higher chamber pressure but does not disintegrate the patch, so there is insufficient 'obturation' (shotgun powder). The other, with a slower powder (H4227), produces a higher velocity with lower chamber pressure and disintegrates the patch. Is this not along the lines of what you are saying, AriM?

As to why Russel started this thread - he's already told us. He had nothing else to do that evening!

yes we are for sure on the same page about the issues. I still think that the term "obturation" is incompletely defined. It makes the assumption that obturation "ends" after the boolit engages the rifling. this would be plausible if you had an absolutely consistent, perfect barrel. you and I know that this is impossible. not just because of manufacturing limitations, but (as you stated very well) the expansion of the barrel. which is totally inconsistent, and dependent on so many conditions (external and internal) and also let's not forget harmonic resonances. which will be different from shot to shot (humans aren't a vice).

so it seems to me that "obturation" (being the bumping of the boolit by pressure/gas to fill the bore) does not in fact end once the rifling is engaged.

I think more and more, this thread is re-enforcing what Mr. Lee has to say, but I also see two camps here.

As far as "Russel" is concerned. I know for a fact that he didn't do this on a whim. I know him on other forums, and via email....and this thing about obturation being a myth, is something he is big on. Not just a whim because he was bored. I am calling you out Brad (lol). I wanna know what you really think about it and why. You are a smart dude, and I wanna know what is going on in your head, that makes you think obturation is a myth.

I have to say, that Star Metals theory about friction generating excessive heat in auto loaders is a fantastic learning point. I would have never thought of it. Maybe it's not such a bad thread. However, may god have mercy on the word "obturation"

I see some serious gaps in it's definition....

I was actually thinking today (after this thread) of building a clear acrylic tube. then chambering it to fire projectiles softer than acrylic (think nerf ball). The charge could be compressed air. That way it could be scaled up and the math could be done to scale up the load (to match pressure and hardness ratios). This would be an easy device to read pressure on (simply use a regulator gauge). They a camera could be set-up to record the travel of the projectile, through the clear barrel. If the camera was at a high frame rate, the footage could be slowed down and the obturation of the projectile could be witnessed. I think this would be a great thing to do. I think it could help a lot of neophyte casters/reloaders really understand the dynamics, and critical ratios that go into a correct load. Who knows in the process I might totally blow my own theories out of the water (or should I say tube)

[felix]

Obturation is actually a medically used term for stopping up wild blood vessels during operations. It actually means to "plug up the pipe so it won't bleed". If we had no expansion going on, and the boolit is a tough one indeed, then leading is almost sure to follow when the elastic limit has not been reached and HELD to the end of the barrel. Thankfully, boolits are not that tough. But, not thankfully, hardness and toughness do not necessarily go together, so its hard to measure if a boolit will lead the barrel or not at a certain velocity. We then are talking shear strength of the lead (alloy). That is somewhat related to the thread herein, but it is hard to pin it down in relation to toughness and hardness. Boolits have to be shot to see what application they are best suited. Suited to BR, tin cans, hunting, etc. ... felix

[Molly]

Hi StarMetal

>Afraid I can't be aboard on the semi auto cases are hotter because they are ejected from the chamber so fast they are still hot. One can shuck a case from the chamber with a bolt gun pretty fast and the case is no ways near as hot at the semi auto.

Yes, but I don't think a bolt action will eject anyhere near fast enough. Try this: Take a semi and a bolt to the range, and just see if you can clear the bolt before the semi can put off 4 or 5 rounds. If you can, my hat is off to you as one of the fastest bolt manipulators I know of.

>You mean to tell me that the time it takes to bolt a rifle that the heat from the case has dissipated to the rifle? I doubt that much.

Well, I really don't have any definitive information here, but you might reflect on the speed at which events occur in the bore of a rifle. A thick steel barrel can be heated in a single shot lasting only perhaps a couple thousandts of a second. I suspect that the same shot will have little difficulty heating a much thinner and less massive brass case to an even higher temperature. Now take that blistering hot case and eject it rapidly. I can tell you from personal experience that the freshly ejected case from even a low pressure round like the 45 ACP is able to peel the skin off of your chest, should you be unfortunate enough to catch it. But if it misses your neck, it will be cooled enough to be handled by the time it has bounced a time or two.

>If you doubt friction can cause that much heat are you aware of welding metal by friction?

Oh, I am aware of frictional welding, though I have zero experience with it. I just doubt that it plays a significant role in this situation. I've been wrong before, and it wouldn't surprise me greatly to be wrong again. But like the fellow from the deep south, I'd like to see some evidence - and not just theories or speculations - before I accept the notion.

>By the way I'd love to see you shoot a Swede at high velocity with some degree of accuracy with a normal alloy without lube or gas checks. That's not crowing on my part, I just find it hard to believe. I know there are some that can shoot bare alloy bullets with success.

Well, it really isn't so hard to do. Start well below maximum loads, and add a volume of Cream of Wheat that is roughly equal to the volume of the neck and shoulder. Take up the extra space in the chamber / case with a pinch of cotton.
Start with midrange loads to get the feel of it, and to develop confidence. Now simply increase your load as prudence would suggest, never going beyond reloading manual maximums for a similar jacketed bullet.

Give the rifle a few shots to condition the bore before each session. I find notably reduced accuracy if the bore is wet or greased. How much accuracy? Well, you aren't likely to win any matches with them, but the accuracy is more than adequate for routine applications like deer hunting. All my records are packed away, but I seem to recall typical accuracy in the range of 2 to 3 MOA groups from my Sweds.

You may encounter problems closing the bolt with your first loads. This happened to me until I traced it to an oversized neck due to the unsized bullet. Depending on your mold, you may see it too. If so, just size the bullet, and otherwise use it without lube or gas check. You will be gratified by the bright clean bore these loads produce. They will also function with squib loads, but too light a load can result in a CoW plugged bore that will try the patience of a saint to remove. I speak from experience.

[AriM]

Obturation is actually a medically used term for stopping up wild blood vessels during operations. It actually means to "plug up the pipe so it won't bleed". If we had no expansion going on, and the boolit is a tough one indeed, then leading is almost sure to follow when the elastic limit has not been reached and HELD to the end of the barrel. Thankfully, boolits are not that tough. But, not thankfully, hardness and toughness do not necessarily go together, so its hard to measure if a boolit will lead the barrel or not at a certain velocity. We then are talking shear strength of the lead (alloy). That is somewhat related to the thread herein, but it is hard to pin it down in relation to toughness and hardness. Boolits have to be shot to see what application they are best suited. Suited to BR, tin cans, hunting, etc. ... felix

yes, I have actually found more than a few definitions for the term. however, the definition in most online dictionaries (when relating to firearms) does say

"obturation refers to the process of a bullet or pellet, made of soft material, flaring under the pressure of firing to seal the bore and engage the barrel's rifling." they all seem to follow that description. the key element being that the boolit bumps until it engages the rifling. that seems very incomplete to me, and leaves a lot of thing unaccounted for. I am not sure that it is just simple semantics here. It is a suggestion, that obturation stops, once the rifling is engaged. I can't get on board with that. Seems that most of us feel that way. Even if we say it a different way.

I think that shear strength is a very valid discussion, and I really do like your point about toughness vs. hardness. They should not be confused. Linotype is certainly hard, but certainly not tough. It would be a horrible projectile for steel targets. Even if it was loaded to the correct pressure. Equally bad for game. So again your points are great and inline with the accepted standards (and I would expect no less from someone of your experience).

I think that there are many unknowns to be discovered, but "obturation" (in it's clinical understanding) seems to be a freeway system, that leads to the same end. It happens. Physics does allow for compression of solids. I made this point many months ago (maybe on page 6 or so of this thread). The only reason we have to say certain states of matter are or are not compressible is to fit standards based table and calculations.

In fluid dynamics, we have to assume that fluid is not subject to compression, or we would never have a standard to base our variables around. This works for mechanical sciences and for statistics, but it violates basic Newtonian physics. It also assumes that there is no unifying theory to be had. I digress.


I think the real topic to debate/discuss/ponder collaborate on here, is more related to the extent that obturation (in it's clinical definition) extends. In my opinion and based on my own tests and research and readings. Obturation can also be married to external ballistics. Or in lay terms. I don't end when the little lead thingy hits the rifling

[StarMetal]

Molly,

22 rimfire cartridges don't have enough powder in them to make them skin burning hot, but yet casing shucked out of an auto loader with burn you.

Listen to this true story. One of my really good friends had a Rem 742 in 30-06 many years ago, which by the way shot groups that most bolt actions would have a hard time beating. He loaded it using the Lee hand loader. Yes you read right, a Lee hand loader and using the rounds in a semi auto. So here we have a tighter fitting cartridge then a fully resized one or factory round. He shot three shot groups with it. Starting with a cold rifle he fired three shot and remember he had the magazine full. Left the rifle in the sand bags and we walked up to the target to look it over. When we got back we noticed one the ejected cartridge had melted all the way through the styro foam cartridge containers that Remingtom loved to use. We noticed the other empty casings were a deep blue from heat, I'm talking about like gun bluing and this was from the case mouth to about halfway down the case. The rifle didn't do this with factory ammo or fully resized ammo. Now you tell me that's not friction heat. That cold rifle also wasn't going to get the barrel hot enough either to warm your fingers on, which it didn't.

[felix]

Everything compresses somehow, sometime if the following holds water: A "black hole" location is a FINAL resting place for all matter in its magnetic neighborhood. ... felix

[AriM]

Everything compresses somehow, sometime if the following holds water: A "black hole" location is a FINAL resting place for all matter in its magnetic neighborhood. ... felix

actually the newest school of science/physics, is saying that no true singularity exists. Rather the event horizon is comprised of many smaller/less dense singularities orbiting a larger central mass. The proof of this is fluctuations in gravity pulse measurements. Gravity waves if you will. The theory states that gravity propagates faster than light. In wavelengths so long, that we can't measure them, yet. Very soon the gravity wave observatory will go into service. It is comprised of 3 probes, spread across immense distance. They are used to triangulate point of origins of gravity pulses (that is the theory anyhow).

Wow talk about off topic. You are a smart guy Felix. I like reading your posts and replies. They make me think.

So I pose this question. Since all matter compresses, obturation does occur to some degree, ANYTIME mass meets pressure meets density. It might be minimal, but it is a constant state of flux. This is where Mr. Lee's writings end, and my own opinions begin. It is also quite possible, that I am just an idiot. Who knows? It's all relative.

what's yer point of reference?

[Multigunner]

Well in the words of Al Bundy "in Wanker County everything is relative", that goes for fluid compressibility as well. Fluids aren't truly incompressible, they are relatively incompressible compared to other substances.
First real world example I remember studying was the use of gasoline in the bouyancy tanks of deep diving bathyscapes. Gasoline is lighter than water but relatively incompressible, so water pressures of a great many atmospheres had little effect on the structure of the tank. If air had been used the tank would have to be built like a bank vault to withstand the pressures.

The only real question about obturation is not if it happens but how. Theres no all encompassing answer to that, due to the very wide range of bullet types and power levels involved.

Now as to gas pressure itself, without resistence there'd be nothing to work against. In part resistence can be friction or mechanical force required for engraving of the bullet. This holds with most breechloaders, but would not explain the Pope style false muzzle loading rifles with seperate propellant cartridge. With those rifles the bullet is pre engraved before any gas pressure is applied and not forced into a tighter throat. So obturation in this instance requires a different source of resistence, purely a matter of inertia of the heavy bullet resisting the application of a motive force.
Hold a water balloon in your hand, raise your hand quickly, and the balloon wil fore shorten and expand evenly in circumference at its equator. The molecules are forced against each other.
Under great pressures metal can flow like a fluid, just as it would if heated to the melting point. Ice at the bottom of a glacier can remain a crystaline solid yet still the glacier flows like a very slow river.

Most confined propellants deliver a greater thrust on initial ignition than later in the burning cycle, mainly due to overcoming initial resistence. But the application of force seldom stops there. The propellant charge will continue to apply force to accelerate the projectile, and the G force of acceleration so long as it lasts will continue to result in the fore shortening and expanding action, forcing the bullet body into the grooves.
When a bullet is driven down a badly eroded bore it can reach portions where the inside diameter is greater than it was at the throat. If the bullet can still expand to fill the grooves all well and good, but if the force of acceleration has dropped off then blowby results heating the surface of the bullet , which can result in jacket separation or in the case of cast a melting and softening with loss of surface integrity, leading to leading and skidding in the grooves and further blowby.

If the bore is rough due to corrosion or built up fouling a bullet that has lost impetus through blowby can seize in the bore at the next constriction and blow through. I've seen a blown through lead bullet before, stuck midway in a discarded rifle barrel.
In the old days stuck bullets were disolved in place using mercury as a solvent, the main mass of the bullet drilled out using a drill softer than the bore steel and the barrel plugged with some mercury inside to soften or disolve whatever was left in the grooves.
A bore that bad would generally require lapping to put it back in usable shape, or more often be discarded.

Blown through jacketed bullets were usually forced out by various means. The 1903 220 gr .30 bullets shed jackets so often a jacket removal tool was issued at one point, intended for every cleaning kit. It was in the form of a mild steel cylinder that fit on the end of a rod, with negative image of the bore and beveled leading edges to pry the stuck jacket out of the grooves.
Once milder propellants were adopted for the .30-06 the tool became a very limited issue item, seldom needed.

Very light loads of fast powders may only apply significant acceleration forces for the first few inches of the bore, past that point the bullet is left to more or less rattle its way to daylight, with increasingly looser fit to the rifling as it goes. The small charge having burned out early on won't cause much noticable blowby, the volume of gas being small.

Experiments with extremely long .32 S&W barrels formed by welding lengths of barrel liners together into barrels about ten feet long or longer, I forget the exact length. Allowed the experimentor to find out exactly when the small charge exhausted its ability to accelerate the bullet, and measure effects of friction on the bullet once the propellant had been exhausted. At maximum length the bullets either stopped or just fell out the muzzle. The barrel was cut back in increments and velocity measured at each stage.
Similarly tests on early production CCI Stinger and Viper cartridges, when they first began showing up on the US market at least, indicated these were optimised for the very short barreled trappers guns popular in Canada , and this made them a good choice for handguns.
Testing showed the cartridges gave maximum velocities from a 16 inch barrel with velocity dropping at barrel lengths over 16 inches. Short barreled .22 rifles were very popular items at the time, and still are to some extent.
The fast acceleration and quick burn out of those cartridges meant they were less efficient in traditional longer barreled .22 rifles, velocity wise at least, but there was next to no influence on the bullet exiting the muzzle, since there was little to no muzzle blast as such.

Well thats a wordy and to some extent repititious post, repeating much of what I said earlier.

It occurs to me that a few drawings would explain the mechanism of obturation far better than all the posts on this thread.

[Molly]

Hi Starmetal

>22 rimfire cartridges don't have enough powder in them to make them skin burning hot, but yet casing shucked out of an auto loader with burn you.

Interesting. Did you just say that a 22 doesn't have enough powder to make the cases hot unless they are fired from an autoloader? No, I know you didn't, but that's what I got on the first reading. (VBG) What you say is still not inconsistent with my proposal that the auto-ejected case simply doesn't have time to cool before it hits your skin.

Enough about my mental excentricities. You have claimed that the real cause of hot cases is friction from the chanber walls if I understand you correctly. Why not actually test the notion? Fire something (22 or 30-06, I don't care) and find some way to test case temperature. Maybe it'll melt into a block of parriffin. Or styrofoam. Whatever. I don't care how you test the temperature, just test it. Then wax a few rounds and see if the reduced friction is detectable in whatever temperature test you come up with.

You can even fire two nearly simultaneous shots from your autoloader, pick up the cases and judge temperature with your hands. (Fire the unwaxed case first, so there won't be any residue to confound your results.) I'm betting there won't be any detectable temperature difference between the two cases, despite what should be a substantial reduction of friction.

>Listen to this true story. One of my really good friends had a Rem 742 in 30-06 many years ago, which by the way shot groups that most bolt actions would have a hard time beating. He loaded it using the Lee hand loader. ...When we got back we noticed one the ejected cartridge had melted all the way through the styro foam cartridge containers that Remingtom loved to use. We noticed the other empty casings were a deep blue from heat, I'm talking about like gun bluing and this was from the case mouth to about halfway down the case. The rifle didn't do this with factory ammo or fully resized ammo.

I'd sure like to know why not. Factory, unsized or fully resized makes no difference: When the round is fired, all of them will be clinging to the chamber walls with all the force that the propellent can exert. Sizing or lack thereof normally makes absolutely no difference except in ease of chambering. Under factory 30-06 pressures, that brass case had all the structural resistance of a bit of tissue blowing in the wind.

>Now you tell me that's not friction heat.

I just did, at least in my opinion. Your story - though interesting - seems to have some logical inconsistencies, and lacks some easily performed tests on its validity.

Now may I tell you what I suspect may have been happening? I wasn't there, and can't possibly know for sure, but I've seen some very strange things done by begining reloaders using beginner tools like the Lee Loader. One of these brethern poured his powder out on a sheet of paper and scrapped up a pile of gunpowder that "looked big enough". This was then decanted into a case and topped with a jacketed bullet. Enough said?

As an aside, this in no way refelcts poorly on the Lee Loader. They can produce excellent ammo, and I still have several in my own inventory. When I just want a couple of rounds to test some notion, they are better suited than my Dillon presses.

I've also seen brass cases discolor toward blue from serious overloads. The worse the overload, the deeper the blue. I think that's enough said too.

Now I REALLY don't mean to belittle either you or your friend. God knows, the idiocies that I performed as a beginner don't give me any leeway to make fun of anyone else. It takes a special kind of fool to see if he can fire a 35 caliber bullet through a 6.5mm bore. (Believe it or not, it CAN be done, but I sure don't recommend it!) And I suspect that I've made just about every mistake that it is possible to make with cast bullets. But I honestly think that you have simply misinterpreted what you have seen.

Firearms can do some very strange things. My father swore to me that he had once seen a 30-06 barrel which had the bullet depart the bore about halfway down the barrel. And he was an aircraft gunnery sargeant at the time, and would have had ample opportunity to see strange things.

An interesting test you might try just occurred to me. Find an automotive garage that has a hydraulic press, with an owner that will indulge you for a few minutes. Cut the base from a 30-06 case, and slit it down the side so you can unroll it into a sheet of brass. Drill an attachment hole in one end and place it in the press under some pressure. Lacking a press, put it under a three foot stack of bricks, and then under a six fooot stacn of bricks. Pull the brass sheet out and check the temperature. Then double the pressure and test it again. I'm willing to bet heavily that within the limits of your ability to pull the brass sheet out, you won't find any differences in temperature.

[AriM]

This holds with most breechloaders, but would not explain the Pope style false muzzle loading rifles with seperate propellant cartridge. With those rifles the bullet is pre engraved before any gas pressure is applied and not forced into a tighter throat.

Well thats a wordy and to some extent repititious post, repeating much of what I said earlier.

It occurs to me that a few drawings would explain the mechanism of obturation far better than all the posts on this thread.

Are Pope and Schutzen rifles the same thing?

All of our replies have been wordy repetitions of the same thing. That was my overlying point. We all get it, but explain it a different way. Which leads me to believe that the word "obturation" itself is not fully defined. We need a more thorough word.

On the issue of drawings, did you read my post (a few posts back) about the acrylic, simulated barrel. I think building that and making the information available, would really help a lot of folks. Please go back and read it, and tell me you opinions. I would need help doing the math, to recalculate correct pressure ratios. I do have a lot of the parts necessary to build it though. Including the acrylic tubing.

[StarMetal]

Hi Starmetal

>22 rimfire cartridges don't have enough powder in them to make them skin burning hot, but yet casing shucked out of an auto loader with burn you.

Interesting. Did you just say that a 22 doesn't have enough powder to make the cases hot unless they are fired from an autoloader? No, I know you didn't, but that's what I got on the first reading. (VBG) What you say is still not inconsistent with my proposal that the auto-ejected case simply doesn't have time to cool before it hits your skin.

Enough about my mental excentricities. You have claimed that the real cause of hot cases is friction from the chanber walls if I understand you correctly. Why not actually test the notion? Fire something (22 or 30-06, I don't care) and find some way to test case temperature. Maybe it'll melt into a block of parriffin. Or styrofoam. Whatever. I don't care how you test the temperature, just test it. Then wax a few rounds and see if the reduced friction is detectable in whatever temperature test you come up with.

You can even fire two nearly simultaneous shots from your autoloader, pick up the cases and judge temperature with your hands. (Fire the unwaxed case first, so there won't be any residue to confound your results.) I'm betting there won't be any detectable temperature difference between the two cases, despite what should be a substantial reduction of friction.

>Listen to this true story. One of my really good friends had a Rem 742 in 30-06 many years ago, which by the way shot groups that most bolt actions would have a hard time beating. He loaded it using the Lee hand loader. ...When we got back we noticed one the ejected cartridge had melted all the way through the styro foam cartridge containers that Remingtom loved to use. We noticed the other empty casings were a deep blue from heat, I'm talking about like gun bluing and this was from the case mouth to about halfway down the case. The rifle didn't do this with factory ammo or fully resized ammo.

I'd sure like to know why not. Factory, unsized or fully resized makes no difference: When the round is fired, all of them will be clinging to the chamber walls with all the force that the propellent can exert. Sizing or lack thereof normally makes absolutely no difference except in ease of chambering. Under factory 30-06 pressures, that brass case had all the structural resistance of a bit of tissue blowing in the wind.

>Now you tell me that's not friction heat.

I just did, at least in my opinion. Your story - though interesting - seems to have some logical inconsistencies, and lacks some easily performed tests on its validity.

Now may I tell you what I suspect may have been happening? I wasn't there, and can't possibly know for sure, but I've seen some very strange things done by begining reloaders using beginner tools like the Lee Loader. One of these brethern poured his powder out on a sheet of paper and scrapped up a pile of gunpowder that "looked big enough". This was then decanted into a case and topped with a jacketed bullet. Enough said?

As an aside, this in no way refelcts poorly on the Lee Loader. They can produce excellent ammo, and I still have several in my own inventory. When I just want a couple of rounds to test some notion, they are better suited than my Dillon presses.

I've also seen brass cases discolor toward blue from serious overloads. The worse the overload, the deeper the blue. I think that's enough said too.

Now I REALLY don't mean to belittle either you or your friend. God knows, the idiocies that I performed as a beginner don't give me any leeway to make fun of anyone else. It takes a special kind of fool to see if he can fire a 35 caliber bullet through a 6.5mm bore. (Believe it or not, it CAN be done, but I sure don't recommend it!) And I suspect that I've made just about every mistake that it is possible to make with cast bullets. But I honestly think that you have simply misinterpreted what you have seen.

Firearms can do some very strange things. My father swore to me that he had once seen a 30-06 barrel which had the bullet depart the bore about halfway down the barrel. And he was an aircraft gunnery sargeant at the time, and would have had ample opportunity to see strange things.

An interesting test you might try just occurred to me. Find an automotive garage that has a hydraulic press, with an owner that will indulge you for a few minutes. Cut the base from a 30-06 case, and slit it down the side so you can unroll it into a sheet of brass. Drill an attachment hole in one end and place it in the press under some pressure. Lacking a press, put it under a three foot stack of bricks, and then under a six fooot stacn of bricks. Pull the brass sheet out and check the temperature. Then double the pressure and test it again. I'm willing to bet heavily that within the limits of your ability to pull the brass sheet out, you won't find any differences in temperature.

Molly,

I can assure you my friend is a very careful reloader and those loads weren't overloads. We had a chronograph with us too I'll have you know. How hypocritical of you to come back and say that because you really don't know a reason why it happen. It happen because the cases were only neck size and I believe perhaps the bolt opening sequence may have been out of timing a little and being the cases were about chamber size to begin with being neck sized only they were still obturated to chamber walls and extracted forceably adding to the heat of the case in addition to the powder combustion.

Let me clear some things up for you. I never meant that friction solely is responsible for all the heat in the case. Another hypocritical thought on your part to think that I am so foolish as to thing that. This also applies to the 22 case not burning enough powder to make the case searing hot.

Still waiting for your explanation and response on the tremendous heat generated on airline brakes which is beginning to become a problem for engineers to design a brake out of a material that will hold up.

Maybe your childhood experience in firearms and reloading (which I doubt that you were that young when you say you starte) have diluted your mind to delusion of grandeur.

Regards Pal

[303Guy]

actually the newest school of science/physics, is saying that no true singularity exists.

I have long thought this. Umm... this does relate to obturating lead alloy somehow, right?

So, should we not find a more suitable word for the expanding boolit. Do we all understand 'upset' to mean lateral plastic deformation of the boolit?

Just a thought on why a boolit should 'uset' laterally without crushing the lube grooves - compressing or stretching a body does not result in tensile or compressive deformation, rather it results in shear at an angle, something like 45° (in a ductile material, anyway). This is why the shear strangth and the compressive strengths are not the same. This means that an 'upsetting' boolit would deform laterally a lot more than axially. (I've only just realized this!)