"Extreme" boolit lube, The Quest...

[runfiverun]

got the box today..thanks again bruce.
i was casting some 22 cores when the box come this afternoon,it was near dinner time anyways, so i shut down and opened the box.

inside was some neatsfoot oil,sulpher ester,and lard oil.
i was gonna make another batch of e-yellow lube, but decided to just work with what i had to see how they would affect the lube.
so i melted down 2 oz's of lube and added 1 tsp of each to three batches to see how they reacted.
the lard oil seemed to add some tackyness to the lube.
the sulpher and neats foot added some slip to the lube.
the neats foot oil seemed to add a bit of softness and mixed in nicely.
and the sulpher acted like it dried the lube just a little [this one might work well with a little less b-wax]
i lubed up 5 of each by hand so i can poke at them a little over the next few day's.
i'll let the lube rest for a couple of days and see how they look, i might add a bit more of each to the lube.

[C.F.Plinker]

Gear. My thinking was that in 10 inches of travel down the bore the boolit would make one complete turn. The circumference of a circle of .308 inch diameter is 3.14159 times the diameter or .97 inches. (It looks like I was typing numbers in the calculator too fast and entered .380 instead of .308. Thanks for catching that.) The arctangent of .097 is 5.5 degrees. 2625 times the sine of 5.5 degrees is 252 pounds.

[popper]

Gear, I looked at Larry's pressure curves, the peak is (I assume) when the Cb is getting 'sized' and accelerated, then drops off rapidly. You and I differ on which end of the bbl 'uses' the most energy, I think it is the chamber end. My reasoning is: 1) assume the CB has constant acceleration (linear increase in V). 2) the CB has momentum. 3) F=M*A. M doesn't change, F decreases so A must also. I think the result is a logarithmic velocity curve and the same for the land force. I did a simple calc for the actual land thrust force, given the .004 land height and ~1" bearing surface and came up with ~200k #. That can't happen, Pb can't take that force. I'm trying to re-write the external ballistics program to try to figure out the bbl dynamics - I'll see how far I get.

[felix]

The lands must create a path alongside a projectile. Destruction is intended, and obturation is required to control the resulting material excretion to be uniformly distributed. The best lube for the application will force ALL of the excretion into the sides of the boolit rather than creating fins at the tail of the boolit. No such lube exists, and a compromise must be made between boolit hardness, toughness and lube slickies, toughness to assure commensurate rotation with velocity at the barrel's end. ... felix

[runfiverun]

felix.
that just gave me a little more insight as to what needs to happen.
by leaving the g/c area open it will accept that extra lead and the lube will flow into the cut corners to seal the imperfections.

this is why it's important for the lube to be able to flow [wet] right at the start when the cuts are being made.
the second stage of lube flow [wet] is to cover the pressure dropping off behind the boolit.
and the third part is where the carrier is wet enough to be flung from the boolit at the muzzle.

[popper]

Felix - that is what we desire, but typically doesn't happen. Looking at many of the retrieved CBs (thanks 303guy) we see 'fins' in lube grooves and bases. There are many extruding and metal forming lubes that work quite well. R5R is right, we need a good 'forming' lube, low 'friction' lube for velocity and be able to get rid of it when it's job is done. Gear desires to get this over a large temperature range, BruceB has provided some test materials (thanks) but is requesting some factual requirements for the lube. I've done some simple calcs to try to get realistic numbers, as well as some ideas to get good numbers, but don't have the equipment for the tests. I haven't used felix lube, but I have looked at the formula and believe I understand what each component is doing. I thik gear will agree with me, any thickeners or hardeners will hurt low temp performance.

[Montana Ron]

Bentonite is a abrasive, I owned 45 acre claim of Bentonite, it polishes hardened steel and hardface to a chrome finish..............sure as hell wouldn't be firelapping a barrel just for the fun of it............you'll ruin a barrel and I hope you arn't selling this stuff to un knowing people.........

[geargnasher]

Bentonite is a abrasive, I owned 45 acre claim of Bentonite, it polishes hardened steel and hardface to a chrome finish..............sure as hell wouldn't be firelapping a barrel just for the fun of it............you'll ruin a barrel and I hope you arn't selling this stuff to un knowing people.........

Have you actually read any of this thread, or are were you too busy jumping to conclusions?

Gear

[DrB]

Gear, I looked at Larry's pressure curves, the peak is (I assume) when the Cb is getting 'sized' and accelerated, then drops off rapidly. You and I differ on which end of the bbl 'uses' the most energy, I think it is the chamber end. My reasoning is: 1) assume the CB has constant acceleration (linear increase in V). 2) the CB has momentum. 3) F=M*A. M doesn't change, F decreases so A must also. I think the result is a logarithmic velocity curve and the same for the land force. I did a simple calc for the actual land thrust force, given the .004 land height and ~1" bearing surface and came up with ~200k #. That can't happen, Pb can't take that force. I'm trying to re-write the external ballistics program to try to figure out the bbl dynamics - I'll see how far I get.

Popper, I've been meaning to get around to this calc to get psi loading on the lands for a while. The outline I worked out goes:

Get max linear acceleration of bullet (should be maximum just forward of the chamber). This can be approximated using a pressure time curve or an internal ballistics code that allows for variations in muzzle velocity with barrel length.

Convert to angular acceleration using a no skid assumption and the barrel twist rate.

Calculate the angular inertia of the bullet... Assume it is a homogeneous cylinder as this will get you in the close ballpark (this simplification will tend to slightly overestimate torque/pressure required).

Using angular acceleration and angular inertia, you can now calculate the maximum torque applied by the rifling.

You can approximate the torque rifling pressure by taking the rifling height, multiplying by the number of lands, and multiplying this by the engraved total bullet length. This is the drive area. Next take half the bore diameter plus half the rifling height. This is the action arm of the torque. The pressure will be the torque divided by the action arm divided by the drive area. (Pressure times drive area equals rifling drive force, times action arm gives the torque).

Pressure will be slightly higher than this as pressure acts on the normal to the surface and there is a component which retards bullet acceleration. You should divide by the cosine of theta, where theta is the angle the rifling makes with the bore line. Theta is given by invsin(pi*bore diameter/twist length), right?

If you have any trouble completing the above, or think I've made an error, please let me know and I will finish it, if it would be helpful.

I also think you should calculate the pressurization of the lube due to linear and angular acceleration... I have always been interested in that since reading lascs article on lube pumping.

Best regards,
DrB

[DrB]

Gear, its the linear acceleration together with twist rate that results in torque/rifling pressure, not velocity. You could have huge torques at 50fps, and no torque at 3000fps.

Rifling pressure will tend to be greatest towards the chamber, not the crown.

Otherwise, +1 on your post #277.

I am pretty sure a major role of paper patching is distributing shear loads to the bullet surface.

[geargnasher]

I'm glad you dropped by, DrB, at this point we really need to settle the rifling pressure thing once and for all. The pressure capability and film strength/thickness of lubricants is easily calculated once we have an idea of the actual pressure requirements.

I know this pressure is due to the continuing increase in linear velocity (acceleration), because if the velocity is constant, the rotational momentum of the boolit will equalize and the torque pressure abates. The work is done creating the delta or change in rotational speed of the boolit from rest to 150K rpm in two feet or less, and in a few milliseconds.

Regarding Theta, or the angle of the rifling tangent to the bore, where Theta is also the hypotenuse of a right triangle with an adjacent leg of (say) ten inches and the opposite leg of (Pi X groove diameter), isn't Theta the inverse tangent rather than sine?

I'm also not sure that even considering chamber pressure in this equation is even a valid point. All I'm concerned with is determining the RATE of acceleration from case neck to muzzle (not a constant due to pressure fluctuation, but perhaps close enough), the inertia of the lead boolit, and the resistance (net) of the boolit to radial acceleration. I can't get my mind wrapped around the net resistance because it requires calculations I can no longer remember how to do, i.e. figuring the net inertia of a cylinder where the outside edge has the most mass and the point in the center has none.

So please help me with the math here, it should be simple enough for an undergrad mechanical engineer with some information on mass, length, and diameter of the boolit to figure the resistance to spin, then we can take that and plug the values for acceleration (figure a constant) and the angle Theta into a simple vector force equation and get our force. That force can then be figured in light of engraving surface area to get us a useful PSI number for our lube film calculations.

It isn't necessary to worry too much about the details of air in front of the boolit, bore friction, chamber pressure, details of rotational mass involving the missing metal from the engraves or the lube groove, or even the boolit nose, just figure it for a cylinder with no engrave marks and we'll be close enough. I also know the force on the sides of the engraves differs from the outer edge to the root of the groove on the boolit, but that is fairly insignificant. We want a ballpark number here, say to the nearest 10K psi would be plenty.

If we could determine this "land pressure" with a useful formula it would help Bruce too, and might solve some of the mystery behind alloy requirements (think of Edd/R5R/Felix's copper content discussions). One of the great things about this forum is all the brainpower here, we have a genuine Tribologist helping out already, a Ph.D mathemetician would be a great help too. I think you understand what I'm trying to calculate, I just can't do it anymore.

PLEASE HELP!

Gear

[DrB]

Love to gear. Give me a day or two and i'll pull it together and paste it in.

Best regards,
DrB

[runfiverun]

probably a cylinder of 1/2" in length would be a good number to plug in.
that would cover most of the bearing surfaces of a lot of boolits available in the 30 cal molds.
and over cover a few. [the long bore ride type]
but thier lube requirements would be basically the same, the friction difference would be made up with a harder alloy anyway's.

[runfiverun]

Bentonite is a abrasive, I owned 45 acre claim of Bentonite, it polishes hardened steel and hardface to a chrome finish..............sure as hell wouldn't be firelapping a barrel just for the fun of it............you'll ruin a barrel and I hope you arn't selling this stuff to un knowing people.........

ron.
you do realize bentone is a grease thickener, and is used for ton's of different formulas.
lard oil is also used in cutting fluid,and in abrasives too.[to keep the cuttings in suspension and flow it away from the working area]
it is still a relevant part of a boolit lube.
many things that are abrasive are useful in a boolit lube if the proper sizes or amounts are used.

[geargnasher]

probably a cylinder of 1/2" in length would be a good number to plug in.
that would cover most of the bearing surfaces of a lot of boolits available in the 30 cal molds.
and over cover a few. [the long bore ride type]
but thier lube requirements would be basically the same, the friction difference would be made up with a harder alloy anyway's.

Part of the problem here is calculating the actual rotational intertia of the boolit. Anything involving a continuing variable, like the mass of a boolit from center to edge, involves calculus, in this case I belive it's a fairly simple definite integral equation where one limit is the center of the boolit and the other is the radius measurement, which I haven't solved or even thought about in over 15 years. I'll need a refresher for sure.

Gear

[runfiverun]

i ain't even attempting that math.
much past figuring center of gravity for an odd shape, volume of various containers,opening and closing pressures of a fracture 10,000 feet down,or btu's.
and i am out of math foo.
but i think friction is part of the equasion, i know it figures in the treating pressure of a well bore,
where a gelled guar is used to carry proppant down a hole [bbl] we calculate friction pressure.

[Marlin Junky]

Part of the problem here is calculating the actual rotational intertia of the boolit. Anything involving a continuing variable, like the mass of a boolit from center to edge, involves calculus, in this case I belive it's a fairly simple definite integral equation where one limit is the center of the boolit and the other is the radius measurement, which I haven't solved or even thought about in over 15 years. I'll need a refresher for sure.

Gear

You'll also need the boolit's profile as a function of x and y (to account for the lube grooves) so can we please get back to boolit lube?

I'm having difficulty reproducing my "on target results" with one of my loads and BAC so I'm really interested in the practicality of what's happening here. I found a load for my '06 using RCBS 30-165-SIL at a BCH under .310" that takes 10 rounds to warm things up before it shoots well. To date, I've only shot a 20 round string with this combo so I don't know how long it takes for the accuracy to fall apart (velocity is around 1800).

Thank you,
MJ

[popper]

I got some pressure data from L Gibson and am working out the forces. Probably be Tues. before I get done. So far my calcs look close. I have to make some assumptions and validate them. I'll attempt to put it in a single concise post.

[geargnasher]

You'll also need the boolit's profile as a function of x and y (to account for the lube grooves) so can we please get back to boolit lube?

I'm having difficulty reproducing my "on target results" with one of my loads and BAC so I'm really interested in the practicality of what's happening here. I found a load for my '06 using RCBS 30-165-SIL at a BCH under .310" that takes 10 rounds to warm things up before it shoots well. To date, I've only shot a 20 round string with this combo so I don't know how long it takes for the accuracy to fall apart (velocity is around 1800).

Thank you,
MJ

This IS about boolit lube, MJ, surface pressure is one of the critical pieces of information a tribologist or lube cook needs. Once we figure out how to determine the moment of inertia for a .308" diameter solid lead cylinder in the 170-ish grain weight, the bearing surface is a separate, and final calculation. First moment of inertia for a disc, then for a cylinder, then calculate the energy devoted to yanking the boolit into a spin using the rifling pitch, then figure the spline surface area of the boolit (rifling depth x driving band length x # of driving bands x number of lands in the barrel), then apply that force over the measured bearing surface to get the pressure the lube film experiences on the sides of the lands, which is very important to the selection of lubricating oil in our formulas, savvy?

I don't understand your question, either. You shot 20 rounds. It took ten to start shooting well? We've gone over and over why we think this happens, and lube is a large part of it. Do you start with a clean barrel? Forgive me if you covered this load in detail before, I don't remember.

Gear

[Marlin Junky]

...I don't understand your question, either. You shot 20 rounds. It took ten to start shooting well? We've gone over and over why we think this happens, and lube is a large part of it. Do you start with a clean barrel? Forgive me if you covered this load in detail before, I don't remember.

Gear

I apologize for my impatience; however, I don't usually get a chance to follow a thread for this length of time and would like to have a new lube concoction to try before much more time elapses. I'll get a chance to retry my 30-165-SIL this week with a seasoned bore.

Thanks,
MJ