Case Head Exits Rifle

[Parashooter]

There is a solution to premature head separations in some of our more flexible actions, but since it goes against a popular bit of conventional wisdom, it's considered dangerous heresy by many experienced handloaders - although a few of us have been using it for years with good results.



Upper case was collet-die neck-sized, reloaded, and fired 10 times in excellent-condition Lithgow SMLE with 180-grain bullet over 41 grains of RL-15 (1 grain under "maximum" per Alliant website data). Case elongated from 2.210" to 2.222" in five shots, was trimmed back to 2.210" and separated on 10th shot. (Case body was stuck so firmly in chamber that chamber cast was needed to remove it - and it still didn't budge until the cast has been driven about 1/4".)

Lower case, from same batch, has been reloaded and fired 15 times with same load in same rifle. Its length has remained at 2.210" - with zero elongation and no internal or external signs of stretch.

The difference? Upper case was kept clean and dry throughout test - lower case received a very thin application of castor oil before each firing.

While it's well-established that lubricated cases allow more force to be transmitted to the bolt face than do dry cases, studies quantifying the difference are rarely cited. According to one impressive-appearing modeling exercise (at Rifle Chamber Finish & Friction Effects on Bolt Load and Case Head Thinning Calculations done with LS-DYNA ) the calculated difference in peak bolt face load between a greased case and a dry case in a smooth chamber is about 10%. If this model is accurate, the difference is barely significant and is in fact less than the normal acceptable variation in peak pressure within a fairly small sample of identical loads.

Whether or not any increased wear on the rifle action resulting from the added load caused by lubricated cases is more important than cartridge case longevity is an individual judgment call. Used with sufficient care (and moderate powder charges), lubed cases can provide a practical alternative to premature separations that may be useful for experienced handloaders who understand the risks and benefits.

Notes: Careful application of thin lubricant coatings should not be confused with the sort of heavy lubrication that can prevent a case neck from expanding and releasing the bullet cleanly - a condition that can produce destructive pressure. Also, oiled cases will collect airborne grit and must be protected from it. An alternative useful in gritty environments is lubrication with a coat of dry wax.

[Jim Tarleton]

Interesting. I had not considered lubricating the brass. It does remind me of the 1903 issues that arose in the early years.

Jim

[Parashooter]

I've noticed that many students of US military rifle lore think of the difficulties encountered with the 1921 "tin can" match ammo whenever lubricated cases are discussed. The actual problem with the 1921 ammo was not case lubricant but bullet lubricant inappropriately applied. To quote Hatcher, "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 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." (Hatcher's Notebook, p 341).

As described by Hatcher, this problem was quite distinct from the added breech thrust occurring when the case body is lightly lubed. Although careless application of excessive case body lube could certainly have the same effect, such a result is easily avoided by applying only a very thin film. I like castor oil for this because it's cheap, super-slick, easily applied, and viscous enough not to run where it isn't wanted. I've never tried the paste-wax approach, but reports from others indicate it's effective (and doesn't collect grit).

[Jim Tarleton]

Was was that chamber cast made of - lead?

Jim

[Parashooter]

Cerrosafe.

[slamfire1]

Lubricated cartridges case myth started with “Hatcher's Notebook” and his section on the 1921 Tin Can ammo. The tin on the bullet jacket cold welded the bullet to the case neck. This created a bore obstruction. A number of rifles were ruined at the National Matches. The Ordnance Department who supplied the ammo, decided to shift the blame to the shooters by blaming an operational practice of the shooters.

They found a unique practice at the time, shooter’s were greasing their bullets to reduce copper fouling. Ordnance claimed that was the reason the rifles blew up. They concocted reasonable sounding theories (all ignoring the bore obstructions that cold welding created) and ran rigged pressure tests to prove their case. Greased bullets were banned for more than 50 years at the National Matches until the original reason was forgotten.

I think the millions of Moly Lubed bullets fired down range have somehow proved the Ordnance theories and tests as bogus. Being a loyal Ordnance Officer, Hatcher reported the theories and failure analysis uncritically. Somehow people reading his book did not see the inconsistencies, and confused greased bullets with case lubrication. This confusion was codified, repeated as fact, time and time again by Gunwriters of the 1970’s and has become a “cultural memory” in the reloading community.

No action is designed assuming that the case provides any friction or carries any load. Take a look at the calculations on Lija’s page and at the article bolt lug strength. Lilja Precision Rifle Barrels - Articles: A Look at Bolt Lug Strength.


I highly recommend visiting the above referenced site and seeing a dynamic analysis of chamber finish/case fricition. Rifle Chamber Finish & Friction Effects on Bolt Load and Case Head Thinning Calculations done with LS-DYNA What I want to point out is that as case friction is reduced, case stretch is reduced. If this is true, it may mean that that cases are less likely to rupture, either through a brass flaw, or through repeated firing, if the cases are lubricated.

[slamfire1]

The lubricated cartridges case myth started with “Hatcher's Notebook” and his section on the 1921 Tin Can ammo. The tin on the bullet jacket cold welded the bullet to the case neck. This created a bore obstruction. A number of rifles were ruined at the National Matches. The Ordnance Department who supplied the ammo, decided to shift the blame to the shooters by blaming an operational practice of the shooters.

Shooter’s were greasing their bullets to reduce copper fouling. Ordnance claimed that was the reason the rifles blew up. They concocted reasonable sounding theories (all ignoring the bore obstructions that cold welding created) and ran rigged pressure tests to prove their case. Greased bullets were banned for more than 50 years at the National Matches until the original reason was forgotten.

I think the millions of Moly Lubed bullets fired down range have somehow proved the Ordnance theories and tests as bogus. Being a loyal Ordnance Officer, Hatcher reported the theories and failure analysis uncritically. Somehow people reading his book did not see the inconsistencies, and confused greased bullets with case lubrication. This confusion was codified, repeated as fact, time and time again by Gunwriters of the 1970’s and has become a “cultural memory” in the reloading community.

No action is designed assuming that the case provides any friction or carries any load. Take a look at the calculations on Lija’s page and at the article bolt lug strength. Lilja Precision Rifle Barrels - Articles: A Look at Bolt Lug Strength.


I highly recommend visiting the above referenced site and seeing a dynamic analysis of chamber finish/case fricition. [url="http://www.varmintal.com/a243z.htm"]Rifle Chamber Finish & Friction Effects on Bolt Load and Case Head Thinning Calculations done with LS-DYNA

What I want to point out is that as case friction is reduced, case stretch is reduced. If this is true, it may mean that that cases are less likely to rupture, either through a brass flaw, or through repeated firing, if the cases are lubricated.

Notes: Careful application of thin lubricant coatings should not be confused with the sort of heavy lubrication that can prevent a case neck from expanding and releasing the bullet cleanly - a condition that can produce destructive pressure. Also, oiled cases will collect airborne grit and must be protected from it. An alternative useful in gritty environments is lubrication with a coat of dry wax

.

I used "stick wax" to coat almost 1000 CAVIM 308 cases. It was a bad idea as "stick wax" is thick and just impossible to wipe off. So I shot the stuff in a FAL The stick wax was on thick and greasey . As I was able to dial down the gas port and have the rifle still function, I know the wax coating reduced breech friction. I did not have any pressure problems. I think as the case neck opens up, any grease or what not is squeezed out to the breech end. The case neck expands first, then the thicker parts of the case after that.

[MEHavey]

Question: Why would not residual case lube (after a cursory wiping down with rag to remove gross excess) perform the same function as carnuba wax/castor oil, etc?

[Parashooter]

• Question: Why would not residual case lube (after a cursory wiping down with rag to remove gross excess) perform the same function as carnuba wax/castor oil, etc?

It does. However, neck-sizing with a collet-style die requires no sizing lube, so if lube is elected for firing it has to be added. If F.L. sizing, I can't imagine using so much lube that a wipedown (cursory or otherwise) would be needed - unless one is enamored of lube dents in one's sized cases.

Personally, I stopped removing sizing lube years ago (unless I'm expecting exposure to grit - or loading .22 Jet revolver ammo). My cases last longer and I save the annoyance of cleaning off lube. Still, this is not a technique for novices or those without a solid understanding of the principles and details involved.

[MEHavey]

Right. (And since I'm a Redding bushing die fan, you gotta point there.)