Steel cases and pressure


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H3R3T1K
December 8, 2011, 05:04 PM
I was wondering about the physical properties of cartridge cases made of steel. Can steel cased ammo be loaded (I'm not saying handloaded) to the same pressures as brass cased ammo? This leads me to my next question. If steel cased ammo is cheaper, why is it that only few manufacturers use it and why do most armies use brass cased ammo? Hope you guys can enlighten me!

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Nick93
December 8, 2011, 07:01 PM
Im not an expert but i think that most military uses brass cases becuase of two reasons ...
one: its more reliable in full auto machineguns ( with out loose chambers like the ak variants) and 2: the machines needed to produce steel cases are different from the ones used to produce brass cases ( they are much more powerfull i think )

Of course the material is a lot cheaper but useally its picken up afther firing and sold as scrap metal or cases for reloaders ...

NOTE: most of military ammo uses mild steel jacket projectiles (copper or brass washed) to reduce cost ...

hope this helps ! Nick

rsrocket1
December 8, 2011, 08:41 PM
Steel is cheaper than brass and many manufacturers do use steel to cut costs. That's why you see a lot of Wolf, Tula, X-Bear ammo in steel cases and they are usually cheaper than brass cased ammo. Even Hornady makes steel cased ammo for cheap shooting (called Steel Match).

Steel ammo must be coated with something to prevent it from rusting pretty quickly. That might be a laquer, a plastic polymer, zinc, copper or something else. If it rattles around loosely in an ammo box, the coating might get scratched and there is a path for rust. Brass does not need a coating and is much more resistant to atmospheric corrosion than exposed steel. Remember armies tend to store their ammo and ship it around where it gets rattled and bumped. Nevertheless, the Soviet Army and Warsaw Pact armies used steel cased ammo for a very long time.

Steel ammo can be reloaded, perhaps just not as many times. I pick up Tula .223 cases and reload them for times when I don't want to/may not be able to pick up my fired cases. I load them to the same charge as the brass cases and have no problems. I don't know whether a virgin steel case is better or worse in terms of catastrophic failure to a new brass case (such as firing out of battery or an overcharge). They certainly work at normal pressures just as well.

rcmodel
December 8, 2011, 08:47 PM
Hornady is buying primed steel cases from the Russian manufactures and loading it here.

rc

SlamFire1
December 8, 2011, 09:27 PM
I was wondering about the physical properties of cartridge cases made of steel. Can steel cased ammo be loaded (I'm not saying handloaded) to the same pressures as brass cased ammo? This leads me to my next question. If steel cased ammo is cheaper, why is it that only few manufacturers use it and why do most armies use brass cased ammo? Hope you guys can enlighten me!

I believe steel case ammunition could be loaded to higher pressures than brass just based on the material properties of steel.

Someone would actually have to do a stress analysis of the pressure vessel given data on the strength of the particular steel at the hardness levels used for a cartridge. Hardness varies throughout the case and that makes a difference on strength. Still, it is hard to believe that any steel case would not be stronger than brass.

Rupture strength is not the issue. The primary reason you do not see more steel case use is breech friction.

Steel cases were used in WW2, these were coated with a chromate coating for rust prevention. The Army had so many issues with stuck cases that in the 50’s there were tests run with steel cases coated with Teflon and wax. The coatings improved the function but, if my recollection is correct, they still were not better than brass cases.

Steel cases do not retract off the chamber walls as much as brass for the same pressure levels. This is very important as virtually everyone has experienced a stuck case. Steel cases stick more often.

Steel on steel also creates a lot of friction.

What you want in automatic mechanisms is a low friction case. The only friction you need is the friction necessary to keep the case from collapsing or from being pulled up the barrel by the friction of the bullet inside the case neck. Apparently there is some friction needed for brass cases. However, once the combustion is done, you want that case to peel off the chamber with no effort at all.

Given the tolerances in cases, chambers, steel cases do not function as well as brass cases.

If the weapon is designed with steel cases use in mind, function can be quite good with steel cases. I believe the AK47 was designed considering the use of steel cases, and that rifle runs steel case ammunition quite well.

I have seen a number of shooters using steel cases in the AR15. The 223 round was a wildcat developed at Bob Huttons ranch by a bunch of guys who were trying to get 3000 fps with a bullet. It was not a highly analyzed or tested cartridge when it went into service with the AR15/M16. The rifle was not highly developed either. The service rifle has always fired brass cased ammunition. Given the past history of both cartridge and rifle, it is no surprise that I have seen a lot of malfunctions in the AR15 with steel case ammunition.

I have not conducted any extensive testing on this, but I am of the opinion that legacy actions built and designed around brass cases will not be as reliable with steel cases as they are with brass cases.

Sport45
December 8, 2011, 10:57 PM
Unless you are blowing out the base of your cartridge I can't see a steel case allowing any greater chamber pressure than a brass case. For every firearm I own it's the gun that limits the chamber pressure and not the case.

Steel may actually hide signs of high pressure by not sticking the same way brass does. I'm not going to try it to find out.

1SOW
December 8, 2011, 10:59 PM
I guess I'm just old and stubborn.
Friction, abrasion, expansion rates and reaction to heat are different with steel vs brass cases. Guns "designed around brass" are going to get brass 'from me'.
If a gun is "designed around steel cased ammo", I'd still probably prefer brass cases.

So far, this attitude hasn't caused any problems. I did stray from this 'once'. I tried aluminum cased pistol ammo. It did extract AFTER I installed a stronger extractor spring in my pistol. I never bought aluminum cased ammo again. Return to 'either' paragraph's first sentence.

fguffey
December 9, 2011, 12:37 AM
I do not live in a dirt, grit and grime free environment, then there are those that advocate greasing cases for slide and glide shooting. Grease in the environment I live in would mixed with the dirt, grit and grime to become abrasive, even though I have never found skid marks on my cases or chambers, I am a big fan of reducing all that case travel and I like the embed ability of brass.

Again, I want nothing between the case and chamber but air, I am a big fan of ‘time as a factor’.

F. Guffey

Jim Watson
December 9, 2011, 10:00 AM
There was the O'Connor Steelhead cartridge.
It comprised a steel head with a brass body screwed into it, available as standard and belted magnum head diameters.
The idea was that the brass body would expand under pressure and spring back after firing for easy extraction while the steel head would not expand or rupture at higher than usual chamber pressure for higher velocity. Supposedly it would let you overload .30-06 into .300 magnum country or a short magnum into Weatherby range.

It would also let you overload .30-06 or whatever you formed out of the basic brass tube to the point it would batter the action. 80,000 psi was mentioned as being within the capability of the case. A conventional brass case is the limiting factor in load levels. If you beef that up, you will just find a weak link someplace else. That might be battered lockup and creeping headspace gains that the steel head would cover up until something went badly wrong.

Cost was probably the main reason it did not catch on, that and the trouble of forming the basic case to the desired caliber and the different loading required by the smaller volume. I don't know if anybody ever stayed with it long enough to beat a rifle to death.

Pictures at:
http://cartridgecollectors.org/cmo/cmo10jun.htm


If you think that is weird, consider the Casull rifle. It uses a recessed case head with an internal groove for the Casull patent extractor. The nose of the bolt is up in the recess and the whole cartridge is in the chamber, full support with a vengance. Unfortunately I cannot find the article and illustrations that I recall.

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