Cases and Enfields and lube - Oh my!

[Parashooter]

Bolt thrust (no friction) is frequently calculated on the inside diameter of the case at the web (since this is the only portion of the base 'touched' by internal pressure). For the .223 Rem. with an OD of .378" and walls .020" thick, we have an ID about .338", radius .169", area .0897". At the proof pressure cited, this would give 6990 lbs. of thrust (remember, no friction). That's as close as I can get to Ed's numbers using the old πr² business. Much depends on what one considers to be the effective thrust area - and there appears to be considerable disagreement, with some using the OD and others the ID at different points.

Of course, using the calculated area x pressure as a bolt-thrust figure fails to take any case/chamber friction into account. If there were perfect adhesion and no case stretch, bolt thrust would be zero - except where the primer backed out. (That's what we look for in the .22 Jet revolver, by the way. Any lube present and the cylinder locks up.) In actual practice we don't see perfect adhesion and we normally see some case stretching in medium rifle cartridges at pressures above ~30,000 psi, which should give us "dry" thrust numbers somewhere between zero and the calculated no-friction result.

The introduction of the "Tin Can" business to a topic trying to deal with bolt thrust at normal pressure is a distraction. The problem in 1921 was excessive chamber pressure, not increased bolt thrust at normal pressure.

The FA tests reported in Culver's "Tin Can" article and also in Hatcher's Notebook, Ch.XIV, were conducted on the 1920 NM ammo with plain cupronickel jacket, not the tin-plated 1921 ammo. Commenting on the 1921 ammo, greased, Hatcher wrote, ". . . if the bullet had been dipped in grease, this generally meant that the neck of the cartridge was greasy too. The space between the neck of the case and the neck of the chamber was filled with an incompressible substance, and the the first moderate rise in pressure found it impossible to expand the neck and release the bullet. Thus the powder was strongly confined right at the beginning of its ignition, and accordingly the pressure rose disastrously." ("Hydraulic lock" is the term I use, perhaps incorrectly.)

Although "cold-soldering" and consequent high bullet-pull with the tin-plated 1921 ammo seem to have contributed to the problem, Hatcher states that without grease, the neck expanded at initial pressure to release the bullet. He seemed to think the thick grease had a crucial role in raising chamber pressure. It probably depends on the type and amount of grease, as well as the fit of the case and chamber. One example of a partially-lubricated cartridge for modern rifle use is the Swiss GP11, which for many years carried a thick ring of waxy sealer/lubricant at the junction of bullet and case, with no apparent problems. The Swiss chamber, however, is made about 1mm longer than the cartridge case, very possibly to provide a reservoir and/or escape route for the lube/sealer.

[Patrick Chadwick]

Yes, it certainly does depend on the type and amount of grease, because of the viscosity-dependent hydrodynamics (the "squirting" aspect).
I have both a Swiss G96/11 rifle and a Swiss 1882 revolver. In the rifle I use only GP11 ammo. In the revolver I have only done some test firing up to now, using the original ammo, which was loaded with black powder. The material used in the Swiss ammo is not grease, but a kind of wax.

I tried a couple of shots of revolver ammo with the wax scraped off. The result was a noticeable soot deposit on the case, indicating inadequate obturation. With the original grease left in place, the cases remained perfectly clean, and in fact there were still traces of wax left around the neck. After firing, the case has developed a very slight neck, but this neck is about 1-2 thou tighter when the grease is left in position (the limited number of shots and unround case mouths make it impossible for me to specify this difference exactly, and it may well be unmeasurable for the rifle). It seems that the grease resists the pressure long enough to present the case mouth expanding fully to fit the chamber. The hydrodynamics of grease will not be the same as for oil, so this observation, while interesting in giving some insight into the workings of Swiss ammo, does not help much in the endless oiled 303 cartridge discussion.

But, going off at a slight tangent away from the oiled 303 case - the GP11 ammo is amazingly accurate in my G96/11. So much so, that reloading seems pointless as long as this ammo is available. And it makes me wonder if we could all stop fretting about oiled cartridges for a while and try the Swiss trick of a wax ring, to see if performance is improved? At the risk of boring those who are still awake (it's after midnight on this side of the pond), I repeat that my personal aim is to get the best performance out of the rifle, not to save brass, and most certainly not to prejudice the rifle in order to increase case life!

Patrick

[slamfire1]

Bolt thrust (no friction) is frequently calculated on the inside diameter of the case at the web (since this is the only portion of the base 'touched' by internal pressure). For the .223 Rem. with an OD of .378" and walls .020" thick, we have an ID about .338", radius .169", area .0897". At the proof pressure cited, this would give 6990 lbs. of thrust (remember, no friction). That's as close as I can get to Ed's numbers using the old πr² business. Much depends on what one considers to be the effective thrust area - and there appears to be considerable disagreement, with some using the OD and others the ID at different points.

I picked the biggest dimension and still did not get Ed's numbers. Maybe the source of his spread sheet found a way of creating energy. More pounds of thrust out than pounds of thrust in. Would'nt Newton be surprised?

I still don't have an answer of what % breech friction to use in designing the next generation of thundersticks.

[Edward Horton]

I picked the biggest dimension and still did not get Ed's numbers. Maybe the source of his spread sheet found a way of creating energy. More pounds of thrust out than pounds of thrust in. Would'nt Newton be surprised?

I still don't have an answer of what % breech friction to use in designing the next generation of thundersticks.

Parashooters figures for bolt thrust for 223 Remington = 6990 lbs.

Ed's figures from Excel for bolt thrust for 223 Remington = 6880 lbs

Difference between the two figures = 110 lbs (my brass cup has less surface area)

No energy was created and actual case measurements vary.

On the .303 case below you would subtract .060 from the out side diameter.



On this .303 case below you would subtract .070 to .080 from the outside diameter. (It depends where the cup or bowl starts in the base of the case.



As you can see Parashooters figures for case wall thickness at .020 were estimates and mine were actual

Therefore Mr. Newton would give me the grade of A+ for my .303 case measurement figures.

Below a Federal .223 case at .027.5 which means you subtract .055 from the out side diameter.



Below a Remington .223 at .033 which means you subtract .066 from the outside diameter.



This means Mr. Newton would again give me another A+ grade and a extra grade point for every .223 case in these two 5 gallon buckets below.



Anyone what wants to question my math figures now for the .223 Remington case.

Now lets oil up some cases and get a little oil on the primers and have some good ol' misfires or even a bullet stuck in the barrel.

[Parashooter]

If I run the numbers for .223 Rem. using .0275" and .033" walls and 77900 psi, I come up with 5956 and 6383 pounds of bolt thrust. Still can't get to your 6884 unless I use .0213" walls. So where does it come from?

In addition, this calculation (interior base area times peak pressure) doesn't factor in any case/chamber friction. It yields the bolt thrust that would occur if there were no friction whatsoever between case and chamber. How can we add 40% to the mathematical maximum bolt thrust to get the "wet" thrust? If anything, the calculation needs to be done the other way. Assuming a 40% increase from "dry" to "wet", the calculated no-friction thrust should be the "wet" column - and the "dry" column should be "wet" divided by 1.4.

Hope you can help us out on this.

[Edward Horton]

Either your figures are wrong or else this Excel program needs re-greased and oiled. It just goes to show you that you can't trust bolt thrust calculations or bad advice given out on the internet about oiling cases.

But I still get an A+ for Mr. Newtons theory that for every reaction there is an opposite and equal reaction.

In 2008 the United States Military told everyone to not lube their ammo, and they gave very good reasons not to do so.
(They could be trying to stop internet myths and rumors)

[jmoore]

Hey, if I rebarrel my No.4 action to 5.56x45, may I please lube my ammo?



BTW, if things work out, going to shoot some modded W-W and R-P 303 cases in an 1981 Westinghouse Moisin this morning (180gr Sierra .311"sp in front of 42.0 gr of IMR4064). If that works, then a 30-30 PMC once fired case w/ a 180gr Sierra sp. and 40.5 gr IMR4064, which is all that would fit w/ the bullet seated about 0.030" into the case. (another old question concerning radial expansion safety limits)





ETA Another contrarian thought just popped into my head- At what point is case "grip" compromised due to increasing case wall thickness???

[Patrick Chadwick]

Dear Edward, Parashooter et al.

There is no point in arguing about a few hundred pounds of thrust. Edward (I think) once produced a lovely animated picture of the stress patterns in a cartridge case on firing. This picture sequence revealed that the whole dynamic event is a lot more complex than any quasi-static pressure over a given area.

I have come to the comclusion that Edward's theoretical approach is OK as far as it goes - that is, to be fair, as far as it can go on the basis of the information available. But only real pressure testing could show up actual peak pressures and bolt thrust. And the results would depend on a lot of factors such as the finish of the cartridge case, chamber wall, head clearance etc etc etc.

As to calculation, the old acronym GIGO springs to mind. I shall not explain that, as it might give offence to those who believe everything their computer tells them. This discussion is, in the end, limited by the simple fact that no-one here has the necessary high-pressure/elevated temperature hydrodynamic and tribological data to make a calculation that exactly matches reality. If that were even possible.

In other words, don't get in each other's hair over these calculation, please!

Patrick

[slamfire1]

Found this on my computer.

From Gunforms.com : Swiss used grease on bullets.

Date: Mar 17, 2002 on 03:29 p.m.
Gren16
2. Re:Wax on GP11 cartridge


The "grease band" on the GP-11 was adopted as early as May 9, 1913 in form of a 7 mm band. 1942 the band was reduced to 4 mm. There are well over 30 variations of the GP-11. Some with, others without lubrication. The grease band was not welcomed by the troops operating in cold weather as the grease accumulated in the chamber and finally made proper feeding impossible. The grease ring had to be removed with a rag - a tedious job. The use of solvents such as diesel fuel was strictly prohibited as it tended to enter the cartridge and made the round unusable.
Date: Mar 17, 2002 on 04:13 p.m.

Big L.E.E.
Normal member
in Gunboards.Com Members

posts: 169
since: Jul 16, 2001
3. Re:Wax on GP11 cartridge



I'm told many Swiss believe the grease ring improves the accuracy of the round. Independent testing by the German Gun Magzine Calibers would suggest this is the case. The found the grease ring improved accuracy by about 1cm at 300m.
In addition, it is believed the grease ring improves the life of the barrel. Around 1981, the Swiss stopped putting the grease ring on GP11 ammo.uch to the dismay of many target shooters. As a result, it is now possible to by tools to add the grease ring to ammunition manufactured without it. See http://www.swissrifles.com/~swissdag...t_greaser.html for an example.

[slamfire1]

As I have stated before, grease and oilers were designed out of small arms. However the historical record shows that there were successful semiauto and full automatic mechanisms that required oil or grease to function.

The Pedersen Rifle

Pg 208; “Cerasine wax is the lubricant used on Filmkote and Keenkot .22 Long Rifle bullets. Being one of the most inert if not the most inert wax there is, it does not have much tendency to pick up grit. These bullets are lubricated by a process patented by Mr. Pedersen, the designer of the .276 Pedersen automatic rifle that was under test by the Ordnance Department a few years ago. In general the process consists of dissolving the proper amount of cerasine wax in heated carbon tetrachloride and with the solution held at the exact temperature necessary, the bullets are dipped. The time they remain in the solution is very important for if removed too quickly the coating of wax will ot only be too heavy but it will chip off easily. It is quite a trick to do even with the proper temperature control and entirely impracticable without special facilities. When the bullets are removed the tetrachloride volatilizes out leaving a thin and almost imperceptible film of wax on the bullet.

The Pedersen automatic rifle operated on the delayed blow-back principle and did not function too well with dry cartridge cases, especially if the cases were hard and did not stretch much, as the setback of the case was necessary to good functioning. As a dry case normally grips the chamber walls, Mr. Pedersen developed this method for lubricating the entire cartridge with cerasine. The thin coating left by his process was not noticeable, did not pick up dirt readily and the chamber heat caused the wax to melt, affording perfect lubrication and certain functioning. The use of this wax in such a thin coating on Cal. .22 bullets offers a good example of its excellent lubrication properties.

Handloader’s Manual, Major Earl Naramore, Small Arms Technical Publishing, 1937

UK World War II Naval 20 mm Polsten cannon.

“The moment of cap strike is critical for advanced primer ignition systems. If it occurs too early the case may be burst; if it occurs too late both the weapon and the case may be damaged. This is less of a problem when low powered ammunition is used but special design features have to be included in weapons firing high velocity rounds. Some of these precautions are best illustrated by the UK World War II Naval 20 mm Polsten cannon…. Firstly, the ammunition was lubricated with grease so the round could move freely in the chamber even when pressure was high. Secondly, the base of the cartridge case and the front of the breech block were made small enough to fit inside the hooded chamber. The round was thus fully supported for far longer than in a system using a conventional chamber and the addition time for safe movement of the case helped to reduce the weight of the breech block to about 18 kg. It would have weighted over 200 kg if the weapon had operated on the simple blow-back system……

Brassey’s “Small Arms and Cannons”, Smith and Haslam.

Japanese M92 Heavy Machine Gun used an oiler. So did the Type 11 and M96 Light machine guns.

Of course oilers and grease went out the door after WWII and the wide spread adoption of gas lubrication. I found this discussion of the origins of gas lubrication on this site:

Gunwriters' Questions and Answers, Part 13.

Example given: Subsequent manager of FIAT company, Giovanni Agnelli, designed a machine gun with a simple construction and a "too much too early" improvement: Fluted chamber (or powder gas lubrication of chambered cartridge), already BEFORE the First World War and several years before introduction of Villar Perosa. Chambers of many Italian machine guns with delayed blowback actions were lubricated with oil for prevention of case breaks. (Idea of lubed chamber was invention of German Andreas Wilhelm Schwarzlose, who designed a first practical machine gun with delayed blowback action in about 1900. Cartridges of earlier Austrian Karl Salvator & Dormus "Skoda" machine gun were also dipped in oil before they were dropped into a gravitation-feed charger of the gun, which was not yet a practical weapon).

APPENDIX: Adoptment of the fluted chamber until 1960's.

Pre-1914: Giovanni Agnelli, Italy. S.I.A. machine gun.

Ca. 1930: Boris G. Shpitalniy & Komarichky, Soviet-Russia.
ShKAS rapid-firing aircraft machine gun.

Ca. 1939: Fyodor V. Tokarev, Soviet-Russia. Self-loading rifle SVT 40. (Just the case-neck space of chamber is fluted).

1944 -45: Illenberger, Jungermann, Staehle & Vorgrimler, Germany. Last assault rifle prototypes Mauser "Geraet 06 H" (without a gas-piston action) and assault rifle "StG 45 (M)".

Ca. 1948: Ludwig Vorgrimler, Spain. (Formerly in France since 1945 until ca. 1947). CETME assault rifle
Ca. 1950: Ludwig Vorgrimler, France. AAT 52 machine gun. (Delayed blowback action was a pre-WW II design of Hungarian Pál Kiraly. Also adopted to FAMAS assault rifle).

Ca. 1956: Schweizerische Industrie Gesellschaft/ Neuhausen, Switzerland. S.I.G. - SG 57 assault rifle.

Ca. 1958: Heckler & Koch GmbH, West-Germany. Modification of CETME rifle (G3). Since 1959 until today: Many pistols, rifles, machine guns, submachine guns and machine cannon..

The Germans even float 9mm cases because they don't want breech friction. Breech friction is bad in any semiautomatic mechanism because all semiautomatic mechanisms fail with excessive breech friction.




As to the pronouncement of the Explosives Safety Group, I find them no more credible than the pronouncements of the Saudi Arabian Court which sentenced Lebanese television psychic Ali Sibat to death for witchcraft. SAUDI ARABIA: Kingdom steps up hunt for 'witches' and 'black magicians' | Babylon Beyond | Los Angeles Times

They are both acting on myth and legend.