Bullet diameter vs lube amount?

[Intheshop]

This is tough because velocity and lube chemistry enter the mix(ha).

So keep the velocity sort of the same...say 1600-maybe 2000.And keeping the lube the same.

Does a .224 take less lube than a .30 or .35?

On my 22-250 @2500 fps,I'm only applying lube to the very bttm,right at the top of the GC....On the 6mm's,only that space and the bttm groove get lubed,@2000fps.

The .30's get either one or two grooves lubed depending on seating depth(OAL).Zero problems or leading with any of the above.These all have VG fits,throat,bore,yadayada.

Is there a rule of thumb or criteria on lube "quantities" and diameters?

Been working 7 days a week,gotta get back now...doh.

 

[Ian]

The only rule is use the least amount you can get by with. The timing of the throat obturation (factors of seating depth, bullet shape, etc) and lube groove design play heavily into how much lube is needed. If not much lube is blown out ahead of the bullet at "lift off", then very little is needed for the remainder of the trip. If a lot gets blown out, a good reserve may be necessary.

I subscribe to Glen Fryxell's definition of "floating fluid gasket" for lube. It seals more than it lubricates, but it has to be very versatile. First, lube acts as a deep drawing wax to help the bullet squeeze into the bore, then it has to maintain bore obturation as the bullet gains speed, and finally it has to basically thin out and be a dynamic film lubricant that can keep up with the bullet all the way to the muzzle even as pressure drops off and bullet alloy relaxes. If obturation is compromised and the bullet leaks, it gas cuts and leads. Lube is a critical part of that obturation.

 

[Chris]

Can we compare the mechanism of liquid lube (surface coat) to lubes occupying bullet grooves?

Clearly we have a lubricating effect, but is the thin coat enough to provide a liquid gasket effect? Does a liquid lube require a more certain obduration effect than traditional lubes?

 

[Ian]

I'll venture that liquid lubes do the same thing. Waxy film at first, quickly turning to a fluid film liquid under friction, heat, and pressure. BLL liquifies even in a short revolver and blows out of the cylinder gap as a fine mist.

 

[Chris]

Perhaps lube under pressure also works like stop leak in a radiator? The tiny gas molecules burrow their way opportunistically into any possible escape route, the liquified wax molecules which are much larger seek the same escape and plug the gaps?

 

[Ian]

I'll go with that. Also, metal salt ("soap") molecules do a fantastic job of holding the mess together.

You'll know when the stop leak fails because you get lead streaks near the muzzle. Ever hear the term "running out of lube"? Well, it isn't exactly that. It's more like running out of obturation because of an alloy/pressure mis-match and the bullet relaxes in the bore, allowing lube blowout along with washing out of some bullet metal. Reverse-tapered bores and lubes which do not go liquid quickly enough will also cause this, as will a rough bore with a lube that has too low of a viscosity for the system.

 

[Chris]

Yeah, I see it that way too. "running out of lube" is related to both the pressure/time curve and maintaining obduration. Got to keep the pressure all the way to the end. Just there's so much less lube involved using liquid and yet it is said to work (I have yet to shoot any but am working toward it).

 

[Ian]

In truth, about the same amount of grease-type is "used" in a well-functioning system. The excess is flung off at the muzzle, or in chunks along the way to the target, causing balance issues. This is why I'm not a fan of gigantic lube grooves, though in some instances they have their place to make a lube bridge going into the throat.

 

[Intheshop]

First off,"stop leak" is bad juju...meaning,I'm riding around,much to my boys constant berating....'95 Buick Park Av,with a 2" crack in the radiator head pce.Stop leak ain't gonna fix it so,I dump fluid in it regularly.

But,if you change the wording just a bit to,"stop gap"....then in my CB pea brain,we're cookin with gas.

Ian's.."if obtruation is compromised",yes on gas cutting and possibly leading but,IME...the boolit "skids".Which is very slightly different from the former.Yeah,there's some leading but it ain't down in the grooves.It's a loose bit of lead up on the lands.Which gets pushed along with subsequent firings.But that's the "minor".The major is we spinning wheels.In sport bike world,spinnin ain't winning.Meaning skidding the bullet an inch or so up the bore,in this case there wasn't any "stop gap"....is a measurable problem.

So,get enough lube at launch,get engraved as quickly as possible....then what?

Do we have to have a lube star?And here is another issue with this sort of question...brrl length.

I like rules....having probably read 90% of Fryxells ,easy to access articles...that was the direction of the OP.Are there rules that state,bore diam,requires X amt of lube?Or is it such a,complicated equation and solution that there aren't any hard N fast answers?

And to reiterate,I'm not having any accuracy /leading issues.Curious.Thanks BW

 

[Ian]

And all I can do is reiterate "the only rule is use the least you can get by with".

 

[Intheshop]

Cool

 

[Kevin Stenberg]

Ian concerning post 6
Are you saying when you shoot a bullet that has just enough push behind it to make it obturate at firing. When it gets to some point still in the barrel the bullet has less power behind it than what is needed to make it (the bullet) obturate. The bullet shrinks back below the die to seal the bore. Thus causing gas cutting and leading.

 

[9.3X62AL]

Enjoying this exchange a great deal, gents. My way of viewing the question relates it to a gas or diesel engine, piston inside a cylinder--the oil/lube functions both as liquid ablative scuff shield and as a component in the compression seal, with the bullet drive bands as an analog to piston rings. Simplistic, I know--but that's how I grasp the concept so far. If I'm missing something, by all means fill in the blanks. TIA.

 

[9.3X62AL]

Since obturation has come up as an element in the lube equation.......would I be out of line to ask for viewpoints concerning an obturation question of my own in this context? If this follow-up is better addressed in its own thread, let me know.

I would like to get an informal survey of the folks here concerning the obturation scale I have seen used in other venues--BHn x 1,422 PSI or LUP = pressure gradient at which a bullet alloy obturates reliably and may produce leading--in essence, a yield-strength predictor for plain-based bullets. The contexts I have often seen this formula discussed in have biases skewed toward "Do not exceed"--and I am not sure I agree with that position. Too many examples IME cause me to disagree with this bias--9mm, 10mm, and 40 S&W in particular. What say y'all? My feeling is that the formula has a whole lot of "cheat" to it--at minimum--but I'm no scientist.

 

[Ian]

Ian concerning post 6
Are you saying when you shoot a bullet that has just enough push behind it to make it obturate at firing. When it gets to some point still in the barrel the bullet has less power behind it than what is needed to make it (the bullet) obturate. The bullet shrinks back below the die to seal the bore. Thus causing gas cutting and leading.

That's it. Lube viscosity and sealing ability at the "relax point" of the bullet can make all the difference between a leaded muzzle-end and a fine-shooting load.

 

[Eutectic]

I think if we 'backed up' to the consideration of how much lube we had in play for a particular caliber in a particular situation, then one may take an internal surface area of the bore of the one that works and then relate the surface area of another bore size taking a percentage change of either more or less lube to theoretically expose the same amount of contact area that amount of lube sees..... Actually this is almost done for you as a similar configuration of lube groove will hold more lube in a bigger caliber and less lube in a smaller caliber.

Ian has it right though! Use as little as you can get away with... (except black powder loads) A GOOD lube will surprise you just how little is needed as long as all dynamics such as bullet fit are all correct.

Pete

 

[Ian]

Since obturation has come up as an element in the lube equation.......would I be out of line to ask for viewpoints concerning an obturation question of my own in this context? If this follow-up is better addressed in its own thread, let me know.

I would like to get an informal survey of the folks here concerning the obturation scale I have seen used in other venues--BHn x 1,422 PSI or LUP = pressure gradient at which a bullet alloy obturates reliably and may produce leading--in essence, a yield-strength predictor for plain-based bullets. The contexts I have often seen this formula discussed in have biases skewed toward "Do not exceed"--and I am not sure I agree with that position. Too many examples IME cause me to disagree with this bias--9mm, 10mm, and 40 S&W in particular. What say y'all? My feeling is that the formula has a whole lot of "cheat" to it--at minimum--but I'm no scientist.

I'm sure I don't agree with Richard Lee. Well, I do and don't. The system he and son developed does work as advertised if you wish to adhere to it, but if that were all there were to the situation we'd never get above 1800 fps with a cast bullet.

This "relax point" thing that Fiver coined may be slightly out of context here. The context specifically involves very high-pressure, high-velocity loads which when speaking of bore obturation require a prefix such as "super-duper" to contain the washout. When pressure falls BELOW the yield strength of the metal (not the putty point, just the point where it can flex and still return to normal shape), that's when lube blowout can occur. This can actually be predicted with QuickLoad and proven in testing. Previously in the barrel the bullet base may have endured 50K psi which will squish Linotype, so you have to realize that this discussion is "relative". If the bullet is launched with a force which never exceeds its ultimate strength in psi applied to the base, and the bullet is tight in the bore, then obturation will be virtually assured all the way to the muzzle.

For the high-pressure handguns, I have never been able to strip a bullet or push one past the obturation failure point. Accuracy failure? Sure. Too hard and too small? Sure, leads to buggary. I'm sure someone has managed to "strip" a too-soft bullet somehow, but I have to wonder if such would be caused by initial engraving washout or from excessive widening of the engraves caused by too much bullet rotational moment for the strength of the alloy, not just overpowering the plug once it's already safely in the barrel.

 

[9.3X62AL]

I'm not a Lee enthusiast, either. I alluded to my empirical impressions when I said there was some "cheat" going on with the high-pressure pistol calibers. I darn sure DON'T want to use gas checks for my 9mm practice ammo--using them for my 357 Magnum/#358156s is expensive and troublesome enough.

 

[Ian]

I believe the "cheat" involves decreasing the slope of pressure build with relatively slow-burning powder...sometimes. Just about every time I try to bundle a statement or comment neatly into a box, a number of exceptions spring to mind.

 

[RicinYakima]

I'll throw the other factor in; obduration is not directly related to BHn. The formula works pretty well for alloys of lead, tin and antimony with the tin being about 1/3 of the antimony percentage and Lyman #2. Anytime you change the structure of the crystals in the bullet, it skews the results, I. e. heat-treating.

I agree with Ian, that looking at the math shown in Lyman CBH #3, that it is not physically possible to make a bullet smaller than bore size by shooting it down the pistol barrel. However, it is easy to get gas cutting to blow pass the bullet.