Case Head Exits Rifle

[Parashooter]

Cerrosafe.

Information

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[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.)

[jamie5070]

Has anyone heard of a rolling block discharging when the block is closed? (A stuck firing pin that hits the primer.) I had heard this some where. I always close the block slowly on my '67 danish in 50-70 when I shoot it.
john

[Kirk]

I've not heard of it happening but I do recall reading that the the firing pin can freeze in place. Some guns were made with no means to retract the firming pin; some were made with coil springs around the firing pin & some have a cam that retracts the firing pin as the block is opened. See DeHass' Single Shot Rifles & Actions.

[Jim Tarleton]

DeHass's book is excellent, and well worth the price for single shot fans.

Jim

[ireload2]

This is an interesting thread. I have 2 comments to add.
A friend of mine had one of the 7mm RRBs. He loaded and fired a single round which blew the breech open. The expanded case was left in the barrel and the primer was impaled on the firing pin in the open the breech block. He took his damaged case back to the gun shop and they produced a 7X57 case they had fired that looked normal. I know the shop well. They are honest but not particularly special gunsmiths.
My friend checked his chamber with a cast and showed it to me. The casting showed the chamber had a slightly shorter neck and sharper shoulder than a normal 7X57 case.
When his cartridge was fired he theorized that the heavy hammer blow drove the case mouth in to the throat causing the high pressure and pierced primer. The pierced primer blew the hammer back and the residual pressure opened the breech block. This may offer a clue to how the breech block opens. A high pressure gas leak may be able to blow the hammer back. It sure blew his open though his primer was pierced to enable it.

In regard to oiled cases. I had read of lightly oiled brass fire forming and stretching less and I began trying it with a 40-65 High Wall. This is low pressure ammo in a massively strong action. The case fire formed well and there were no issues. Next I tried a CZ 527 in .22 Hornet. Then reformed .303 WW and R-P brass in a 6.5X53R Dutch M95 Steyr Mannlicher rifle. The cases fire formed perfectly. Since then I have made it a practice wipe a very thin film of oil on each case as I fire form new brass. All my experience with this had been positive.
I don't plan using this for normal shooting of fire formed brass in a rigid bolt action. For this application it only slows down shooting as my existing brass life is nearly infinite with failures being neck or body splits. I will definitely use this technique to prolong case life in the springy Lee-Enfield rifles and reduce the extraction load on my Hakim extractor.