7.62x51 (inert) Steel case, Lake City, 1956 (Edited: spontaneous decay)

The cartridge appears to be zinc coated steel.
Lake City 1956 with the NATO symbol (circle with +).

Seem to recall reading, somewhere, that there was a steel case development project.
Any additional background would be much appreciated.


Several variations of US 7.62mm NATO steel case cartridges were produced in the 1950s and 1960s. The zinc-cronak plated ones made by Lake City in 1955-1956 aren’t too hard to find. I have several ball variants from both 1955 and 1956 plus an AP loading from 1956. There are also examples from the 1960s that have a phenolic varnish coating on the case.

Below are a couple of examples from my collection. HWS III discusses other variations, and you can download the report “Development of a 7.62MM Cold-Worked Steel Cartridge Case” for information on some of the later steel case developments.

Lake City Zinc-Cronak Steel Case AP, 1956

Lake City Zinc-Cronak Steel Case Ball, 1956

FA Phenolic Varnish Steel Case Ball, 1966

FA Phenolic Varnish Steel Case Tracer, 1966


That is some outstanding background reading…greatly appreciated.
Many thanks,

Hi Chip, great post, thanks!

Here is a picture of a rare box of M61 cartridges with steel case (⊕ LC 56 headstamp). This is the first lot produced by LC.





There is a reference to your item in HWS III on page 230. It indicates it was labeled as M63 and the bullet is just a jacket without a core. Yours looks like it spent some time in a harsh environment at some point, perhaps by intent as a test?


Thanks for the link to that report.


Very nice box there. Thanks for posting that picture.


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DaveE and Fede,
Many thanks for your replies.

Have acquired HWS Vol-1,…will have to redouble my efforts for Vols- 2&3.

The zinc-Cronak coating does appear to have taken a severe beating!



It’s very easy to get HWS Vol. III. See https://historyofammunition.com/ or PM me.

It’s very difficult to get a copy of HWS Vol. II. The last time I checked online at Amazon and AbeBooks, the cheapest was in the $300 range and other copies were in the $425 range. This tempts me to make a PDF copy available as work on Vol. II Revised goes on.

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While it’s not as good as actually owning a copy, you might be able to borrow a copy from your local library via interlibrary loan. Years ago I was able to do so for both HWS 1 and 2. I also borrowed a copy of “SPIW: The Deadliest Weapon that Never Was” using that method, and it ended up coming to me from the CIA library. I’m probably on a list now :).

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Twoaz - I think in the title of that nice report you mentioned
and provided a link to, you have a small typo error in the title,
showing “Cold-Worded” instead of “Cold-Worked.” There were
some 5.56 x 45 rounds made that actually had the initials “C W”
marked on the headstamp of the steel cases.

Thanks for posting that. It is an important document, and opened
o.k. regardless of the minor typo error.

John Moss

Thanks for catching the error John - I just corrected it. I also should have mentioned in my first post that thanks should go to bdgreen for the report. I’m pretty sure he posted a reference to the report many months or years ago on the forum. I wouldn’t have known about it otherwise.

the 5.56x45 John mentions.

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Hi Mel and twoaz,
If only I were in the US rather than Middle-earth.
Books ordered from the US can have a postage penalty of anything from $7-50’s. Copies don’t appear in Middle-earth very often and as a result; 'it’s ‘slow and steady.’

I’ve ordered from the US: History & Development Of Small Arms Ammunition, Vol. 1: Martial Long Arms: Flintlock through Rimfire; by George A. Hoyam and hope to receive it next week.

Unfortunately; the local library service now charge to see; “specialist books.” I enquired recently and it was going to be approx. $30 to loan/view a book.

Therefore; ‘it’s ahead, slow and steady.’

Appreciate very much your thoughts and suggestions.

I have an LC 56 steel case dummy (cronak finish I think) loaded with a ball bullet and what was presumably intended to be an inert filling. An awful electrolytic reaction destroyed the headstamp, primer, and most of the primer pocket. If I hadn’t had this since it was only a year or two old I’d have no clue what the headstamp had been. Perhaps Sam3’s round started out same as mine and was drilled through after the chemical mischief began. Jack

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That is a fascinating observation. Looking again at my example, it looks as though there is a hole forming in the primer.
The Cronak process is described in Wiki as the following:

“The Cronak Process is a conventional chromate conversion coating process developed in 1933 by The New Jersey Zinc Company. It involves immersing a zinc or zinc-plated article for 5 to 15 seconds in a chromate solution, typically prepared from sodium dichromate and sulfuric acid. The process was patented in the United States on March 24, 1936 with USPTO number 2,035,380.”

The chromate solution mentioned above is; “typically prepared from sodium dichromate and sulfuric acid.”

I wonder if the process was ever intended for use with zinc-plated, or zinc-coated mild steel?

Imperfections in the original zinc-coating might have exposed some of the steel to sulphuric acid. Were some cases zinc-coated better, or more completely, than others?

Was this Cronak Process ever commercially implemented for steel cased cartridges?

Are there other examples?


Ask & you shall receive Sam3
All steel cased dummies with the headstamp in question & all have arsenal holed primers. Some of these were thought to have used salt as a inert charge which might explain some corrosion. But even the case-holed dummies show corrosion to the head. I have no explanation.

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Pete: I can state that the filler of my now deteriorated round was a white granular substance. I would think table salt a good bet, if not a good idea. Jack

I have seen a few of these over the years, and have a couple “somewhere”… they have all been deteriorated, at least somewhat.

What did the Ruskies do differently, as I have never seen any of their zink plated rounds corrode like the US rounds, many were/are corrosive priming, and some were definitely not stored under ‘optimal’ conditions.

Maybe they did not use salt to fill inert cartridges?

I bounced the deterioration question off a couple of lab people.
The expected possibilities were:
Deterioration could be from the inside as a result of the steel rusting with exposure to water vapour in the air.
Salt is Hygroscopic and would, consequently, be unhelpful.
There could also be imperfections in the zinc coating that allows the substrate steel to rust from the outside.

I couldn’t find anyone to comment on the chromium (dichromate) coating. This was probably done to provide a more wear resistant or corrosion resistant final finish. The Cronak process might have been poorly performed and the sulfuric acid used might not have been completely removed from the case.

I may be wrong; however, I recall reading somewhere, that there were attempts around that time, to ‘copy’ the lacquer finish seen on East European ammunition. The lacquer coating is, apparently, not trivial and may entail several steps. Getting the coating thickness ‘wrong’ would introduce multiple problems. If I recall, the question arose out of a discussion regarding strategic materials and the cost of brass compared to steel and lacquer.

There is an Article from Nathaniel F. at the following link:


If the filling in my round was salt and if the primer was holed (as I suspect tho my notes don’t say one way or the other) that would be just about right to rust the case as the salt over the years picked up atmospheric moisture through the primer hole. In which case the question is: why on earth did they use salt for a filling? Jack