Cases and Enfields and lube - Oh my!

[Parashooter]

Well, I finally got a chance to put another 20 shots through the .303 case that refused to fail if I kept it lightly lubed. With 35 lubed firings now, it still insists on keeping its head.

Initially, this was a test to compare dry and lubed Winchester .303 cases fired in a good Lithgow SMLE to see if there would be any difference in case longevity - or any damage to the rifle. Having an excess of cheap Remington .311" 180-RN bullets and a near-full jug of RL-15, I picked two old W-W cases that showed no signs of wear or stretch - probably because I usually shoot fairly gentle cast-bullet loads in my Lee-Enfields. I trimmed the two cases to 2.210", annealed the necks, then loaded and fired them with the Remington 180's, 41 grains of RL-15, and Remington 9½ primers. I used a Lee collet die for neck-sizing so there'd be no chance of disturbing the shoulders.

After 5 shots dry, case #1 had grown to 2.222" and I trimmed it back to 2.210". By the 7th shot, the first indication of incipient separation appeared in the usual location about 1/8" ahead of the solid web - after the 9th shot it was really obvious. On the 10th shot the case separated and was stuck so tight I couldn't budge it with a standard "broken shell extractor". I finally got it out by pouring a Cerrosafe chamber cast and driving both cast and case with a flat-ended steel rod from the muzzle.

I then fired case #2 with the same load but put a light coat of castor oil on it before each firing. After 15 shots it still measured 2.210" and showed no signs of stretch or thinning. I checked the rifle for any change in headspace, damage, or wear and found nothing I could feel, see, or measure.

Today I set up the chronograph and kept loading and firing the same case, again putting a thin coat of castor oil on it before each firing. Since there had been no adverse results at 41 grains, 1 grain below maximum per Alliant, I went to 42 grains, which Alliant calls maximum (and lists at 2479 fps with the Speer 180 RN bullet in a 24" barrel). To my surprise, five of these averaged just 2261 fps. The next five, at 43 grains, went 2328. 44 grains averaged 2383 fps. Finally, at 45 grains, the final five shots averaged 2450 fps, what I'd call "service velocity" for a .303. (All I can figure is that this lot of RL-15 is a bit on the slow side. Even at 3 grains over "max" there were no signs of abnormal pressure.)

Please note that this was a torture test, not load development and definitely no kind of recommendation!

That was enough for me. I'd fired a total of 35 shots with this one case. It is still the same length as when I started, 2.210" and shows no signs of stretching or thinning. Except for more scratching and scuffing on the body, it seems not to have been changed at all. Frankly, I was surprised by this. Previous experience leaving sizing lube on cases had given me the impression that lube wasn't effective at preventing case stretch with full-power loads. Maybe putting a fresh coat on just before firing each shot made it work better.

My good old SMLE seems unaffected by this test as well. Headspace is unchanged and there's no added wear I can see or measure. I'm pleased by that since I've had this rifle since 1963 and it's definitely an old friend.



I'll be the first to agree that firing just 45 shots with two cases from one rifle doesn't prove a damn thing. Plenty of genuine authorities who know a lot more than me have said in no uncertain terms that any lubricant should be removed from cases and chambers before firing - because failure to do this might damage rifle or shooter.

I'm certainly not saying I know something all those guys don't. Rather, I'm just the kind of nut who has to try stuff anyhow and thought some of you might like to know how it turned out - this time. Maybe someone seeing this has or will run more/better tests and let us know the results. What I'd really like to see is somebody with one of those Oehler Model 43 outfits slap a strain-gauge on a Lee-Enfield side rail and try to quantify the lube effect on action flex. Now that would be interesting!

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Edward Horton]

Parashooter

With all the discussion of late about oil and grease in chambers and warnings in books and manuals, and after reading about your experiment here I have a few questions.

Benchrest shooters and anyone neck sizing only, have a case resting firmly against the bolt face when it is fired and you do not hear about neck sizing only causing excessive bolt thrust.

When a case is firmly against the bolt face and the cartridge is fired would it be safe to assume you would just have pressure exerted on the bolt without any additional thrust?

A new cartridge is normally shorter than your actual headspace or on average your headspace plus .002 would be the head gap clearance. A commercial case fired in a military chamber would even have more of an “air gap” or head gap clearance.

Would you say from your own experiences and book learnin’ that the greatest danger of damage or wear from bolt thrust is from loose fitting cases slamming into the bolt face?

In this I mean even with oil in the chamber and a tight fitting case pressing on the bolt face it would seem that very little to no additional thrust would be applied to the bolt?

I’m going through a mid-life crises and restudying slippery slopes and my thought processes.

[Parashooter]

I don't have good answers, just some random thoughts about what happens to the case between ignition and when the bullet leaves the barrel.

• If everything is dry and there's moderate end-play (gap), we know that the forward body adheres to the chamber and the rear body stretches ahead of the web. How much pressure this takes varies with the cartridge size, shape, hardness, and thickness.
• Stretching the case uses up some of the energy produced by the burning powder.
• Whatever energy goes into stretching the case doesn't get applied to the bolt face.
• If there is zero end-play, stretch is limited to the amount of "flex" inherent in the action design at whatever pressure is produced on firing.
• Again, any energy used in stretching the case doesn't get to the bolt.

So how much energy goes to stretching the case? I don't know, but I think the calculation goes something like this -

• The cross-section area of the body just ahead of the web is roughly equal to the case circumference times the wall thickness there. In a .303 with fairly heavy-walled cases, that's about 1.4" x .030" = .042 sq.in.
• The area of the solid web face (pi R squared) is about 3.1415 x .2" x .2" = .125 sq. in.
• The "yield stress" of full-hard 70-30 cartridge brass is about 60,000 psi.
• 60,000 p.s.i. times the cross section of the body, .042 sq.in., means about 2520 pounds of pressure goes to stretch the case.
• If maximum chamber pressure is 49,000 p.s.i., total thrust applied to the web face is .125 x 49,000 = 6125 pounds.
• The force on the web face, minus the force used to stretch the body, is what reaches the bolt face. 2520 is about 40% of 6125, so stretching the case as much as possible without breaking it reduces bolt thrust by roughly 40% (worst case, with heavy walls .030" thick where stretched - less with thinner cases).
• If the case isn't stretched that far, or the case is effectively lubed, less energy is used for stretch and more reaches the bolt face. (The NRA Handloading book says British-style axial pressure readings with dry cases are normally about 10% to 20% less than with lubed cases - possibly indicating that neither stretch, adhesion nor lubrication approach 100%, or that my 40% calculation is way off.)
• When stretch isn't enough to deform the case permanently, we're into an elastic situation and I have no idea how to figure that. Hell, I don't even know what "modulus of elasticity" actually means.
• Math makes my head hurt.

I believe our Lee-Enfields were designed and (usually?) made with enough strength and elasticity to handle the full thrust of firing at normal service pressure without depending on dry cases to absorb part of it. Given enough use, any practical shoulder rifle will eventually wear or show some sign of stress. Lubed cases, allowing more thrust to reach the action, undoubtedly accelerate that process - but most of us may never fire enough rounds through our Lee-Enfields to notice it.

I also believe excess lube on the neck can cause a hydraulic-lock condition, especially with tightly-crimped jacketed bullets, that could spike pressure significantly. I suspect this situation is the ultimate source of many of the dire warnings we've seen about lube on ammunition or in chambers.

In the end, it seems to me we have a choice of giving up some case longevity to minimize stress on the rifle or accepting some added thrust to gain extended case life. Of course we "have cake and eat also" when we can use lower-pressure loads that are easy on both case and rifle.

[Peter Laidler]

Wise words there Ed. I have copied them for my next spiel to a technical group next week if you don't mind................ Naturally I'll tell them that they're my thoughts!

[ireload2]

>>>When stretch isn't enough to deform the case permanently, we're into an elastic situation and I have no idea how to figure that. Hell, I don't even know what "modulus of elasticity" actually means.<<<

When dealing with the elastic situation the same calculation used for determining the stretch of the action can be applied to the just the cartridge case. The stress has to remain below the elastic limit of the material.

Here is some mechanical data from Olin

[limazulu]

"If the case isn't stretched that far, or the case is effectively lubed, less energy is used for stretch and more reaches the bolt face. (The NRA Handloading book says British-style axial pressure readings with dry cases are normally about 10% to 20% less than with lubed cases - possibly indicating that neither stretch, adhesion nor lubrication approach 100%, or that my 40% calculation is way off.) "

Yet Ed's post picturing the excerpt that 19 tons psi thrust with a lubed case vs 10 - 12 tons psi with a dry case is about a 40% difference.

[ireload2]

"If the case isn't stretched that far, or the case is effectively lubed, less energy is used for stretch and more reaches the bolt face. (The NRA Handloading book says British-style axial pressure readings with dry cases are normally about 10% to 20% less than with lubed cases - possibly indicating that neither stretch, adhesion nor lubrication approach 100%, or that my 40% calculation is way off.) "

Yet Ed's post picturing the excerpt that 19 tons psi thrust with a lubed case vs 10 - 12 tons psi with a dry case is about a 40% difference.

You might note that the British system was not deemed accurate without oiled cases.

[Edward Horton]

It is my understanding the lubed cases were only used during proof testing of the Enfield Rifles to seat the lugs and bolt head. The British-style axial pressure readings were lower due to the location of the copper crusher pellet. The pressure conversion chart for the crusher pellet would still give the correct pressures readings because they would have been compensated for the crusher pellet location. Oiled cartridges would have a pressure conversion chart just as you have conversions chart for dry torque and wet torque.

To me this translates to less thrust or pressure being delivered to crusher pellet because the cartridge case was absorbing a percentage of the actual force/pressure just like a shock absorber on a car. It also shows more force/pressure is delivered to the bolt with an oiled proof test cartridge i.e. MORE bolt thrust.

Nothing is said about the British base crusher system being less accurate, it simply states the readings were lower than the American axial system.

Proof Loads

(Under the British base crusher standards described below, proof loads ran 30 to 45% above normal. To maximize breech thrust, proof cartridges were oiled before firing.)

In Britain, a third set of crusher standards were developed, using a "base" crusher. The crusher was a short, thick tube placed behind a piston at the base of the cartridge, and the firing pin passed through the center. The cartridge case was well oiled before firing, to minimize cling to the chamber walls (if not oiled, the indicated pressures were about 25% lower). To prevent case rupture on set back of the base, the crusher was first deformed in a press to a pressure a bit lower than that expected in firing. The units were generally stated in British long tons per square inch, or tsi. Pressures indicated by this method run 10 to 20% below those indicated by radial crushers. Kynamco in England still rates their production cartridges with this method.

Please note no reference material is given for the British base crusher method and this website deals with the Powley Pocket Computer, a slide rule type device for rifle load development. (I have one pictured below)

Links below.

The Soapbox of Karl W. Kleimenhagen
Cartridge Pressure Standards
Karl's Soapbox

[Patrick Chadwick]

Well lads, this is a fascinating thread. Taking all points of view on board, and thinking how a responsible designer would have proceeded, I come to the following tentative conclusions:

1) Appropriate light lubrication of the case can reduce the strain on the case and thereby increase case life.
BUT
2) This gain is bought at the cost of considerably increased peak pressure on the bolt head, thereby possibly increasing the set-back of the bolt lugs over time.
HOWEVER
3) No responsible designer would have dimensioned the Enfield bolt so that it depended on dry cases sticking to the walls in order to achieve an minimum acceptable service life. The very fact that the proof load case was lubricated indicates that this "worst case" was anticipated.
BUT
4) What was an minimum acceptable service life? Many of our rifles are probably way beyond it already. Except in the case of NIW rifles, probably no-one knows how many rounds have been fired through his rifle.
SO
5) I do not want to risk shortening the service life of my rifles (Here in Germany it would not be feasible to acquire a sackful of bolts + boltheads to do a mix'n match as a Peter Laidler may be able to do - and fitting a new bolt is a change that requires reproofing of the rifle and registration of the new bolt number in the firearms licence. Even acquiring a replacement bolt head means an entry in the licence (try explaining to those who make the laws that a bolt head by itself cannot fire anything).
ANYWAY
6) In the end, I will always be able to obtain cartridge cases as long as target shooting is practised. But I shall probably never again be able to acquire a straight-out of the wrapper No 4 Mk 2, and certainly not a No. 1 MkV with a mint bore.
THEREFORE
7) I will be going with the O-ring for fire-forming, and still wiping my cases clean after sizing.

Agree? Disagree?

Patrick

[Edward Horton]

Patrick Chadwick

I damaged a .270 Remington 760 Gamemaster because I was using case lube to fire form my cases and the technician at the Remington repair center was the one who informed me to never use any lubrication to fire form any cases and to keep all oil or grease out of the chamber. My cases and chambers have been dry ever since and what caused the damage to my Remington 760 was excessive bolt thrust.

The problem is the oil or grease preventing the case from gripping the chamber walls and the case slamming into the bolt face with excessive force called bolt thrust. The bolt thrust on the Enfield is increased by the amount of head space or head gap clearance on each rifle. (The air gap between the case and the bolt face)

The mating surfaces of the bolt body and bolt head can become peeded and you can actually feel a sharp edge on the outside edge of the bolt body, think of driving a metal stake in the ground and how the top of the stake mushrooms outward. The same can happen to the bolt and lug recesses in the receiver with the corresponding increase in headspace.

Even fire forming cases at lower pressures still creates excessive bolt thrust and the case still slams into the bolt face and the resulting damage is accumulative over time. Decreasing headspace and keeping the chamber dry and oil free reduces bolt thrust, if you can not change your bolt head to decrease headspace then using a rubber o-ring reduces your headspace to zero when fire forming cases and eliminates excess bolt thrust.

Below is a section from Varmint Al’s with links to Lilja barrels and Varmint Al’s on chambers finish and bolt thrust.

POLISHING MY CHAMBERS.... When I got my 223 Ackley Improved Virgin Valley (no longer in business) barrel, it had a very rough chamber. The fired brass had marks I could see where it had been gripped by the chamber and then slid backwards a tiny bit until stopped by the bolt face. It looked almost sandblasted. There were protruding primers on some of the fired rounds. When the firing pin hits the primer, it pushes the primer and the new case forward in the chamber. When ignition occurs, the pressure expands the walls of the brass. The rough chamber, with its high friction, grabs the case at the forward position and the gas pressure first pushes the primer back against the bolt face. As the pressure builds, the brass case is stretched until the case head is pushed back against the bolt or the case supports the total load. If the case head is pushed against the bolt face, it would produce a flat primer, but flush. If the load is light, the case does not stretch so much and leaves a gap between the case head and the bolt face, but the primer is still against the bolt face. This produces the protruding primers.


Lilja Precision Rifle Barrels - Articles: A Look at Bolt Lug Strength

Stolle Panda Bolt Stress and Deflection Analysis

Stolle Panda Bolt Stress and Deflection Analysis

Friction Coefficient Tests of 416 Stainless Steel on Cartridge Brass

Varmint Al's Handloading/Reloading Page

For those of you who oil your cases and say it has no effect all I can say is my rifle was damaged and the warning in books in manuals were put there for a reason.

Don’t shoot the messenger, in order for the forces of nature to work they must remain in balance.



This Simbol(Yin-Yang) represents the ancient Chinese understanding of how things work. The outer circle represents "everything", while the black and white shapes within the circle represent the interaction of two energies, called "yin" (black) and "yang" (white), which cause everything to happen. They are not completely black or white, just as things in life are not completely black or white, and they cannot exist without each other.

Even German engineers understand the importance of Yin and Yang