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

Ian

Notorious member
Bret, if that happens, it happens before the bullet has moved far enough to fully obturate the bore.

ITS said something about in some situations lube would precede the bullet (I think so too in many if not most situations) but I have no idea how he came to that conclusion since there is no way I know of to actually test if lube precedes the bullet down the bore or not wothout a high-speed camera or wire gap technology.
 

Rick

Moderator
Staff member
I think much of that has to do with pressure and lube hardness. The harder the lube the more it has to melt before much of any movement will take place. The softer the lube easier quicker it will flow. Commercial cast almost always use commercial lube which is normally quite hard. I would think the bullets mentioned earlier in this thread found in the berm with the blue lube still in the grooves were commercial handgun and likely Magma hard lube.
 

uncle jimbo

Well-Known Member
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.

I am going to inject something on this subject. As was stated by Ian, I watch all the Gun stories on tv and they show a lot of front of the muzzle shots. On a lot of the shots one can see the "dirty mist" exit the muzzle before the bullet leaves. I have not idea what it is, but there are lots of shots that this can be seen in the slow motion shots. So something comes out in head of the bullets.
 

Bret4207

At the casting bench in the sky. RIP Bret.
Maybe someone can explain it so it makes sense to me, but unless the neck is fully opened before the bullet starts moving, and unless the lube is eroded by the passing gas column to carry some minuscule amount out ahead of the bullet before it is in the leade I have a hard time seeing any significant amount going ahead of the bullet from which it came. Why don't we see lube onthe nose of the bullets we recover? Where I get tied up is the idea that all this happens in a series of repeatable events. It's the same issue I have with the idea of lube "melting" from heat from the gasses. It takes time, even under 40KPSI, for heat to transfer, start the melt and then start to spray anywhere. Meanwhile the neck is opening and the bullet starting to move. We're talking micro-seconds. That's the time/pressure/distance thing I alluded to. Isn't that pressure pushing the lube into the lube groove or any other space too? Shouldn't we be finding bullets with a gap between the GC and bottom part of the bullet full of lube then? The pressure rising in the cartridge isn't pushing forward, it's pushing everywhere until the bullet starts moving and then the pressure moves to fill the space. And if the bullet is one of those Loverins with, say, 8 lube grooves but only the bottom 2 filled, why don't we see evidence of lube in the upper grooves after firing? I'm back to, "I dunno." I don't have the education to put in terms that might sound more scientific.

Unc Jimbo- Yeah, the air in the barrel along with anything ahead of the bullet, assuming a well sealed bore, is going to shoot out ahead of the bullet under compression. Any residual oil, lube, powder ash, dust, etc is going to be pushed out.
 
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Mitty38

Well-Known Member
So Lubing is kinda like treating an unknown illness. First make sure we have other known factors under control.
Start with a basic known treatment that has worked before under similar situations. Modify the treatment( lube) till the undesired symptoms go away.

Lamar-
think I will save that experiment for when I am a little bit further down the Rabbit hole.
 
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uncle jimbo

Well-Known Member
Gas and unburned powder. Are any of those shows using cast bullets?
Some of the guns do shoot lead bullets or in the case of muzzle loader round ball. Lots of older gun are showcased. Like I said, I don't know what the "dirty mist" is, but you can see it. Sometimes it is hard to see the bullet coming out of the what ever it is.
 

Bret4207

At the casting bench in the sky. RIP Bret.
Mitty, that's the "art" part of "The Art and Science...". There are people that can give you their theory and make it sound like it's just gotta be the truth no matter what else anyone says. Then someone else will come along and offer up a completely different theory and sound just as reasonable and dead sure as the other guy. For mental midgets like me, it's all Greek, but if you don't try to understand, where does that leave you? I didn't understand the book keeping our towns accountant was using. I dared ask questions the other wouldn't. Turns out a couple of the questions I asked resulted in him catching mistakes in the way he was doing things and he corrected it. No such thing as a stupid question and all that...
 

Ian

Notorious member
Some of the guns do shoot lead bullets or in the case of muzzle loader round ball. Lots of older gun are showcased. Like I said, I don't know what the "dirty mist" is, but you can see it. Sometimes it is hard to see the bullet coming out of the what ever it is.

I haven't seen a slow-motion video of a cast bullet yet but have seen quite a few with jacketed and there is always a whoosh of hot gas and particles coming out ahead of the bullet. Just ONE video showing a cast bullet coming out of a pistol muzzle would pretty much prove the lube blow-off theory, especially if the bullet were seen clearly enough to examine what was left in the grooves.

Copper jax always leak (which is one reason for copper fouling, same mechanisms of abrasion and gas-cut powdered metal deposition as from undersized or too-hard cast bullets) but usually cast bullets obturate the bore better so we should only see blowby from cast during the initial part of the launch, while the bullet is making the case to bire transition. Breech-seated cast bullets shouldn't leak at all.
 

Rick

Moderator
Staff member
On ignition as pressure begins to build and before the bullet starts to move the case will start to expand outward releasing the bullet, in that small bit of time before the bullet gets to the rifling and starts to seal the bore some gas and unburned powder will be ahead of the bullet. How much should depend on many things such as how close a fit the brass is to the chamber, how pliable or brittle the brass, how much pressure, distance for the bullet to move before sealing.
 

Ian

Notorious member
On ignition as pressure begins to build and before the bullet starts to move the case will start to expand outward releasing the bullet, in that small bit of time before the bullet gets to the rifling and starts to seal the bore some gas and unburned powder will be ahead of the bullet. How much should depend on many things such as how close a fit the brass is to the chamber, how pliable or brittle the brass, how much pressure, distance for the bullet to move before sealing.

Yes, exactly!
 

Brad

Benevolent Overlord and site owner
Staff member
It isn’t just heat that causes lubes to go liquid, pressure plays a role as well.
Add a shear force to some substances and they go more liquid. This is a good thing for our lubes as that means they can be thicker at rest, like in storage, but go more liquid under pressure for lubing and on firing. That is what a thixotropic Means.

I have recovered rifle bullets with lube on them. I have also had targets at 100 yards with lube boogers on them. This means the lube is still flinging off 100 yards downrange. I don’t like lubes that do that.
 

Bret4207

At the casting bench in the sky. RIP Bret.
On ignition as pressure begins to build and before the bullet starts to move the case will start to expand outward releasing the bullet, in that small bit of time before the bullet gets to the rifling and starts to seal the bore some gas and unburned powder will be ahead of the bullet. How much should depend on many things such as how close a fit the brass is to the chamber, how pliable or brittle the brass, how much pressure, distance for the bullet to move before sealing.

So the guys with tight necks with almost zero clearance should have way less leakage and see more lack of lube issues? Has anyone seen evidence of that?
 

Bret4207

At the casting bench in the sky. RIP Bret.
It isn’t just heat that causes lubes to go liquid, pressure plays a role as well.
Add a shear force to some substances and they go more liquid. This is a good thing for our lubes as that means they can be thicker at rest, like in storage, but go more liquid under pressure for lubing and on firing. That is what a thixotropic Means.

I have recovered rifle bullets with lube on them. I have also had targets at 100 yards with lube boogers on them. This means the lube is still flinging off 100 yards downrange. I don’t like lubes that do that.


Time/pressure/distance, I get that. I even get the pressure causing easier liquefying of a lube, even if I didn't know the word to describe it. With the vast variety of loads used out there and vast variety of fit variables of the cartridge in the chamber, it seems unlikely that any hard and fast rule can apply to the theory that lube is blown out ahead of the bullet it came from in an amount that would would be visible even at 10K frames a second from a clean bore. I think this one is going to remain unproven theory for a long, long time.
 

Bret4207

At the casting bench in the sky. RIP Bret.
ITS, I wouldn't even know where to begin on the idea that stuff is "blowing back" onto the outside of your case necks other than to mention brass spring back. Many of us see soot on the upper portion of the case mouth, but rarely down the length of the neck. That is usually indicative of an underload. Again, we're in the pressure/time/distance dimension. The pimples you describe sound a lot like oil spotting. I'm assuming your chamber is oil free when this happens?

30 (or 45) vs 22 re-lube quantity should be a fairly simple progression, maybe even involving good old Pi, but I bet it's not. Quality is another thing entirely and I think Fiver has kind of delved into that can of worms.

Trying to get an understanding of why and how this stuff works is not only interesting to me, it was that curiosity that got me asking question of guys like Felix that resulted in the light going on one day regarding fit. I'm not foolish enough to think I can figure women out, but maybe I can figure some of this cast stuff out!
 
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Ian

Notorious member
So the guys with tight necks with almost zero clearance should have way less leakage and see more lack of lube issues? Has anyone seen evidence of that?

What you get then is a clean lube moustache on the case mouth from lube being displaced by engraving and filling the small space between the end of the case and the end of the chamber. Lube demands are otherwise very low due to conservation at launch.
 

popper

Well-Known Member
Lube leaves a thin layer on the barrel surface that is 'blown 'out next shot. Low pressure loads leave a space between neck and chamber wall for gas residue and lube, as do high pressure loads. Compression pressure on waxy lube liquifies it (pressure is work/heat on the wax). My fast 308 loads with veggie oil lube left necks damp on the outside and a nice runny lube star at the muzzle. Fast moving air in front of the bullet has little momentum but will strip lube off the barrel walls. I H.T. after PC and don't use ANY tin, just Sb,Cu and As in my rifle alloy. I did try some Zn & tin (1% each) for the 30/30 as an experiment - worked fine - only with GC, @ 1800 fps (185gr). Expands great - 30 in, 45 out of the gut of a hog. I eliminated the L.G. from the 31-165A, just a very small collector groove. Nose fits the bore (slight jump), body fits the throat. Same idea for 300BO mould and great performance. XCB may be better for target work, never tried it.
 

Rally

NC Minnesota
Well let me be the first to show my ignorance! In my mind the pressure has to have some hydraulic affect on the lube (hard or soft) during obturation (SP) which must force some lube into the gas column prior to a complete bore seal. It makes sense in my mind, there would have to be some lube, in whatever form, in that gas that escapes around the bullet, ahead of the bullet. Maybe it is deposited in the bore/ separates from the gas, and ironed out/ spread on the bore by the bullet as it passes. I believe it must be all to some degree, and the higher the pressure the farther it must travel.
Something else I've wondered about, while sizing/ lubing a big run of bullets, is it likely the gases first displace lube in the minor air pockets in the lube grooves, left from trapped air, as the lube fills from different ports in the sizing die? Always seemed like it would give pressure a "Toe Hold" in that process.

Bret,
I feel your pain, when these conversations on lube and displacement start! I just picture lube as grease in a bearing grease rig. New grease in (pressure) old grease out (bullet lube). It doesn't make sense to me that lube is all blown out each shot, or there wouldn't be any left to preserve/ lube the bore during subsequent shots, and viscosity and flashpoint of the ingredients in the lubes vary, so the amounts deposited in the bore would vary.

Brad,
A lube star makes sense to me, but lube boogers on the target at 100 yards doesn't. Seems like uneven distribution of lube on a bullet traveling that far would be detrimental to accuracy/ balance.
 

Bret4207

At the casting bench in the sky. RIP Bret.
What you get then is a clean lube moustache on the case mouth from lube being displaced by engraving and filling the small space between the end of the case and the end of the chamber. Lube demands are otherwise very low due to conservation at launch.

That assumes good fit and the guy loading the tight necked gun isn't pushing things, wouldn't it?
 

Bret4207

At the casting bench in the sky. RIP Bret.
Rally, I just have a hard time buying into the theory, and it is only a theory, that any significant amount of lube can somehow preceed the bullet into the bore. Some seem to make the assumption the pressure is only directed forward, or something along those lines.