Casting Session, NOE 310-165-FN (30 XCB)

Ian

Notorious member
I think the two most important grooves on a cast bullet are the front one (usually a crimp groove) and the space in front of the gas check.

All that metal in the "shoulder" area of the bullet that we use for alignment and guidance for the nose tends to need to be bigger than groove diameter because the throat is bigger than groove diameter, and as that part squeezes through the throat that metal needs to be directed somewhere on purpose or it will cause the whole cross-section of the bullet at that point to start to flow (usually in ways we don't want, like the nose extruding in a curl like sausage coming out of a grinder). The crimp groove is often generous and lets the shoulder flow back into it with relatively low resistance, thus keeping engraving resistance low (remember that is good for preserving the parts of the bullet that are pushing it) and keeping the metal displacement limited to the outer layer of the bullet rather than squeezing and choking the bullet all the way through.

Veral Smith and others state that the space above the gas check is a reservoir for the lube, powder residue, and metal that the gas check scrapes off the bore. There needs to be enough space there, but not too much. Yes, you fill that space with lube, that lube is generally blown out as soon as the primer is lit, along with a little from the next groove or two forward. 45 2.1 mentioned one time that he thought a little lube being blown off the top of the grooves and forward before the bullet got fully corked up in the bore was one of the mechanisms by which bullet lube works. I tend to agree.

If you look at some photos of the NOE XCB bullet recovered after being shot at very high velocity that Larry Gibson has posted, you will notice some bad flame cutting on the back two driving bands. He used a rifle with a matching taper and a very tough, hard alloy (heat treated #2). The pressure to move that bullet against full shoulder contact with the throat, and alloy being very tough, causes the gas pressure to build very fast and high before the bullet can move and that gas is trying every which way to get by the obstruction. The bullet made of such alloy does not exhibit nearly as much gas damage if it is fired from a .308 that has a stepped throat because the steps cut into the bullet's shoulder gradually as the bullet moves forward out of the case neck. The XCB bullet also lacks a particularly deep front groove that would also ease engraving pressure. This bullet seems to like being sized .310" most if the time, less metal to move.
 
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Ian

Notorious member
To my everlasting dismay, I remelted a big hand full of recovered bullets that would really help explain this stuff. I did find this one to compare to unfired.

Several things of note. You can't see it in this photo but the 2.5/2.5 air cooled alloy blows up the nose into the grooves nearly to the ogive when launched with 50K psi. One thing you can see is the lube groove is narrower and larger in diameter. Some of that happened when it was fired as the shoulder flowed back and the "stem" of the lube groove squished up, and some it happened in the trap as it stopped. Also note the tiny little bit of flame cutting on either side of the land engrave on the base band. This is an example of minor flame cutting. The alloy is about 13-14 bhn and was coming out the muzzle in the mid 24s.


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Bret4207

At the casting bench in the sky. RIP Bret.
Veral Smith and others state that the space above the gas check is a reservoir for the lube, powder residue, and metal that the gas check scrapes off the bore. There needs to be enough space there, but not too much. Yes, you fill that space with lube, that lube is generally blown out as soon as the primer is lit, along with a little from the next groove or two forward. 45 2.1 mentioned one time that he thought a little lube being blown off the top of the grooves and forward before the bullet got fully corked up in the bore was one of the mechanisms by which bullet lube works. I tend to agree.

Okay, let me direct this thought to that part of the sentence in italics. The primer lights, powder starts to burn, pressure rises more or less equally within the case to the point the bullet starts to move out of the neck, the pressure forces the neck open somewhat, the bullets into the leade and engraving and up the barrel it goes. What mechanism is "blowing" the lube out of any of the grooves? I've heard this theory before, likely reading Verals stuff, but I have a problem seeing how the lube is going to be "blown out" at all unless the groove is compressed, like squeezing an orange. I'm not saying it's wrong, I just don't get the force that would cause it to be blown around when I find lots of bullets with lube in the grooves after firing. I can see the bullet being compressed by the pressure and as it exited the case mouth and hits the leade and the lube being "squished" outward and then coating the following parts of the bullet. I can also see the rotational forces moving some of the lube outwards, especially at the muzzle. But I've heard others describe the lube being "forced", or "blown out" as you say, and I get stuck there. "Blown out" sounds like gas pressure pushing on the lube particularly and moving it. The pressure should be more or less equal surrounding the bullet even as the neck opens a bit. If anything, I would think the increasing pressure would tend to cause the lube to compress INTO the groove, not out of it. But I don't have a degree in anything, so I could be dead wrong.

Comments?
 

Ian

Notorious member
The gas pressure can and I think typically does work around the bullet base and up the sides of the case along the bullet in microscopic jets. It stands to reason that a little bit of lube gets washed out with it and spritzed into the throat. I've seen lots of pistol bullets in the berm with 99% of the lube remaining in the grooves, so I know what you mean, but I'm speaking mostly about rifle bullets here, and high pressure, which I think Bob was as well.
 

Will

Well-Known Member
I always though of lube acting like a hydraulic seal. I used to think that lube helped the groove to deform uniformly. That was until I started seeing recovered powder coat bullets.

I was always amazed by how much a lube groove shrunk when fired.
 

fiver

Well-Known Member
lube will flow under pressure just as much as it will under just heat.

I don't know if we really want to delve into lube makeup and the attributes of each component at this point, but you are gonna be modifying what your using or changing the volume you use at some point.

I done an article over at boolits titled something like 'does your lube have enough friction'.
probably doesn't exist anymore though.
But.
let's think about why a lube would have a friction value, or why you'd add in a modifier to change when/ where that lube is actually starting to 'flow', how long it continues to flow, and what you'd do to it to keep it flowing all the way to/past the muzzle.

Felix liked to talk about a lube's viscosity.
I try to carry that through from point A. [just sitting there]
to change number-1, through change number-2, into it's third point of change or exchange, and the final phase.
change 1. heat and compression.
change-2 pressure and friction
change-3 is when the pressure on the bullet is released.
this can be in the barrel or at the muzzle.
and the final phase is when the bullet leaves the muzzle.

if a lube is going through all of those changes and exchanges it starts to make sense how it can be influential or influenced, and how it can be helpful from point A through change number-1 in holding it's place on the bullet [providing support to the lube groove] or having the outer skin or more removed allowing that point in the groove to become a weak point.
weak points are exploited under stressors.
 

Bret4207

At the casting bench in the sky. RIP Bret.
The gas pressure can and I think typically does work around the bullet base and up the sides of the case along the bullet in microscopic jets. It stands to reason that a little bit of lube gets washed out with it and spritzed into the throat. I've seen lots of pistol bullets in the berm with 99% of the lube remaining in the grooves, so I know what you mean, but I'm speaking mostly about rifle bullets here, and high pressure, which I think Bob was as well.


So the lube gets gas cut and that pushes the lube around?
 

fiver

Well-Known Member
maybe gas cut maybe just sucked off the top and blown forward.
have you ever used a real slippery thin lube in a revolver or semi-auto and found it like all over everything including your hands and shirt and hair and inside the magazine?
or could taste or smell it.
it's like one of those spray bottle where you turn the nozzle down and it just barely sprays a mist when you pump the handle and pressurize the liquid inside but then restrict where the pressure can go.


anyway.
here is something to think about when your thinking about the bullet taking up the hit into the barrel.
think about it like pushing a bullet into a size die [LEE type or a star] but instead of using a press handle and moving it in there at like 1 or 2 feet per second your doing it at 200 FPS.
you can feel the bullet hit that slight amount of resistance just before you push it into the sizing portion of the die.
now that's a solid polished open ended smooth surface and if it's clean and dry and your bullet is clean and dry you can 100% feel the difference between that scenario and one where your following a lubed bullet or a series of lubed bullets.
hit it dry 4-5 times in a row and you really feel the resistance change.
[with a star sizer your probably gonna stick the bullet in the die after a couple of dry ones]
your not even doing anything stressful to the bullet really, your just slight changing it's diameter.
but you definitely feel that slight pause when it gets there.
 
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Mitty38

Well-Known Member
Check me if I am off here.
I was under the impression that a very small amount of lube wicked off past the groves in the micro seconds before the bullet got a seal in the bore. Like almost a mist, spraying the throat and lands.
After reading here a bit I have ben thinking that also...

The lube would be traveling the same feet per second after the initial blast, and the denser lead bullet gets up some speed.
So after initial blast, and gaining a velocity, it would stay put like a ball will, if you sit it down in the bed of a truck traveling 55 mph. Because it is moving the same speed.

Afterward the initial acceleration it would wick and flow just like it would if you applied heat and friction to it while it was standing still. But not from force of the blast. Lubricating the bullet front and back coating it and thus the bore through capillary action.
That the use of softer lube in low speed loads was to get more of this initial effect in low velocity pistol loads.

I kinda think it is why Alox tumble lube does so well compared to the harder wax type groove lubes, with low velocity pistol loads. (At least in my experience) It is already coating the driving bands contact surface and it is greasy enough to blow around then wick and flow a bit.

I think that is on line with what you are getting at.
 
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Bret4207

At the casting bench in the sky. RIP Bret.
I don't think anyone KNOWS for sure. What we have is a lot of guys that are way smarter than the average bear offering up what seems to be reasonable theories. I have an issue with the pressure pushing lube anywhere idea. I won't write out the whole thought process I get into, but there is time under pressure to be considered along with variables in the lube filling the grooves and their depth. What does make some sense to me is the idea of the bullet accelerating out of the case and hitting the leade and then slowing some as the pressure rebuilds. I can see some lube getting tossed around then. But that doesn't answer the paradigm where the bullet is hard into the lands. What it comes down to is I dunno. Why do softer lubes fail at higher speeds as a very general rule? I don't think anyone is shooting Lee's Mule Snot at 2800fps. Why do some bullets shoot better with less lube? Why doesn't all the lube fly off every bullet? Where is the tipping point between lube viscosity and pressure and the "spritz"? Where is my Phd in Hydraulics or whatever this is? I dunno. I'll stand by and let greater minds than mine offer up their thoughts.
 

Rally

NC Minnesota
The variables are mind boggling to me. Change any component, alloy or lube and a whole set of variables again, not to mention what the bullet encounters after it leaves the muzzle!
 

Ian

Notorious member
Hard lube can stay on a bullet all the way into the dirt even while the hard, undersized bullet gets gas cut from gas blowing all around it. Almost always a softer, larger bullet with soft lube will jettison clean lube specks and dirty lube spray within inches of the muzzle (I've tested this). The dirty mist either preceeded the bullet or came out with it, I'm inclined to believe the former but without a video camera capable of at least 100,000 frames per second there is no way to tell.

So the real answers are "we don't know" and "it depends", depending on the question (specifics of the components and dimensions of the system in question).
 
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Rally

NC Minnesota
I've always wondered what percentage of the lube we apply is actually burnt, coats the barrel, and how much actually leaves the muzzle. I've cleaned out enough indoor ranges to know a lot of hard lubes stay on the bullets. I've yet to find any lube on a rifle bullet, even in snow.
 

Mitty38

Well-Known Member
Seems like I pick up a lot of 45 acp lead with blue lube, on Saturday mornings. (Get every other one off.) Some one uses it religiously almost every Friday at our range. The bullets look like the ACME 45 ACP 185 Grain SWC .
The blue seems to empty the grooves out about one quarter way when it is warmer out.
When it is below 40 degrees or so, they look like they have not lost a bit of lube on their journey. When they hit the sand bank, if it weren't for the refiling marks, they would actually look like you could just load them up and shoot them again.
I would love to catch him shooting some Friday( if I ever get one off work). Then ask him-or her if they notices a difference in accuracy with that lube- those bullets, when it gets colder.
I am almost betting his accuracy drops when it gets cold, and it is because of the lube he uses.
 
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fiver

Well-Known Member
I can send you some of that lube [same formulation only red] if you really wanna find out.
you just gotta heat it up to about 120-F to get it to flow in a lube sizer.

I know super soft lube gets sucked or blown off a bullet even at low pressure and velocities.
I have a lube tuned for my 9mm to shoot in below 32-F temps, once it gets up over 40-50 I get a gun full of bullet lube.
heck I get a hand/mouth full of it too.
no leading or anything and the accuracy isn't all that bad, even when it's hot out, but man what a mess.
 

Mitty38

Well-Known Member
I can send you some of that lube [same formulation only red] if you really wanna find out.
you just gotta heat it up to about 120-F to get it to flow in a lube sizer.

I know super soft lube gets sucked or blown off a bullet even at low pressure and velocities.
I have a lube tuned for my 9mm to shoot in below 32-F temps, once it gets up over 40-50 I get a gun full of bullet lube.
heck I get a hand/mouth full of it too.
no leading or anything and the accuracy isn't all that bad, even when it's hot out, but man what a mess.
CAN IT BE PAN LUBED???
 

Bret4207

At the casting bench in the sky. RIP Bret.
Isn't there also a theory that at least some lubes under pressure turn liquid on the surface and it flows that way? That one gets me back to the heat/time/pressure issue and why aren't my necks interior awash in lube, or burnt lube to follow some other theory? I dunno. Maybe it's just one of those "We don't know what we don't know" things. Scientists and those with much higher education seem to have a hard time with the idea we don't know what we don't know, but for a guy like me it's practically a rule up there with Murphys Law.
 

fiver

Well-Known Member
but then your also dealing with the thixotropic nature of a lube.
I chased down a lube that I was hoping was going to become a fully thixotropic lube as pressure and heat was applied to it, had it down pretty good too.
perfecto... right? solid in the case and throat and liquid at the muzzle.
good luck timing that one out.
then when you do some goof ball comes along and changes the ambient temperature 40-F upward and your pushing something resembling toothpaste gel out your muzzle in short order.

Emmett.
can it be pan lubed?
umm no,,, it'd be similar to pan lubing paraffin blocks only not quite as brittle and with a higher melt point.
 

Bret4207

At the casting bench in the sky. RIP Bret.
See. this is where we get into one persons observations leading them ot one conclusion and anothers leading them to a different conclusion. For instance, outside of a case of extreme gas cutting, I can't see how lube can be blown out the muzzle ahead of the bullet the lube came from. Lube from a previous bullet, yes, but not from the one in the bore at that time. Maybe it can, but if it is you've got to have some serious fit issues in play in my mind.