National Arms Co. - Zip Chambers

Hi, All…I have recently acquired a complete set of Zip Chamber and components, including instructions, for .30-40 Krag. I would like to know all I can about the history of the company. We know they were located in San Francisco, CA., with at least two different addresses. I have two patents relating to the chamber and its use, and a 1932 ad from Outdoor Life. I also have a red and blue box containing 50 bullets and 50 blanks. The chamber box states “Patents Pending” and the patents were issued in 1933, so would guess this dates from about 1931-32 ?
Thanks, All…Randy


Very nice. If I’d seen a Zip adaptor before Ray’s recent post I don’t remember, and now I’ve seen a whole set in fantastic condition! Best of luck on your info hunt.




Who made the blanks for National Arms and what is the headstamp?


Well, since nobody else asked, I will. What was this ZIP chamber used for?

Zip Chambers were simply a short-range practice device. they used a separate bullet loaded into the device, lead I believe, for indoor shooting or other short-range application. Similar but not at all identical to the European CONUS rounds.


Who made the blanks for National Arms and what is the headstamp?

The blanks were made by Remington and, have the U headstamp.
M. Rea

Very soon, I will post pics of the bullets and blanks…the bullets are lead, and apparently, when new, were cadmium plated, although we may not be able to see that now. As Mora said, the blanks were made by Remington, with impressed U headstamp. National Arms Co. even touted the use of Kleanbore priming…

Thanks for sharing.
I would be very interesting to see the instructions.

Martin…I will post scans of the instructions…(The set in the photos is still on its way to me) If you look at the photo of the chamber itself, basically, the bullet is inserted into the neck (forward) end, just like a regular cartridge. The .22 RF Blank is inserted into the rear of the forward portion. The two pieces of the chamber are then screwed together. The rear portion contains a spring loaded firing pin, which, when struck by the firing pin of the rifle, is driven forward to discharge the blank, expelling the bullet down the barrel.

The bullets that I have for the 30 caliber chambers are CN jacketed, 93.5 grains.

If you’ll look at the other thread on the “Adapters & Aux cartridges” you’ll see instructions as I copied them from an original set. A back issue of the JOURNAL also has a reproduction of an original instruction sheet.

Not all of the chambers and/or kits are alike (Randy’s is in a wooden box) and the instructions will vary too.


I just received a bunch of good info on the Zip Chambers from Dale Spahr. The first bullets used were cadmium plated lead. Then just plain lead. After that 98 grain jacketed bullets for .30 caliber. So Ray’s at 93.5 grains are pretty close…

To all: The Zip Chamber was patented by Alonzo F. Gaidos of Redwood City CA on March 21. 1933 (1,902,771). They were made of mild steel. The blanks were quite powerful and several sizes and pitches of threads were tried to eliminate the “sticking” of the joint from thread deformation. Have never seen one but the last type was supposed to have been a bayonet joint. Many types of lettering were used on the cases. There were also several types of “grips” used to open the devices from none to several types of knurling. I have 10 examples, boxes of bullets, lead CN, copper jacket. Two configurations of propellents were used. Straight and bottle necked. Bottlenecked could be used in straight chambered Zip’s but not the other way around. Have never seen a propellent box marked as to which type it contained. Am a member of the Remington Society and have inquired without sucess several times about any records having being found of any correspondence or orders from Gaidos for either blanks or bullets. Have one 30-06 Zip Chamber that has obvious plier marks where someone used them to unscrew stuck threads to open the chamber. The chamber is blackened like the owner must have tried to “home” flame harden it in desperation. Several years ago contacted several people by the name of Gaidos in the San Francisco area to see if they were related to Alonzo, none had ever heard of him. Have also researched the CA state archives and corporate records without success. So have come up against a brick wall trying to find anything about the company. Gaidos also patented several large units for sighting artillery with centerfire cartridges but apparently never manufactured any. By the way found out the name Gaidos is a corruption of the Hungarian name Gajdos this from a native Hungarian, according to him it is not a common name.



That is great information. Thanks. I’m making a copy for my files.

How many different calibers of Zip Chambers were there? I have 300 Savage and 30-06 plus one cardboard box of components. I have never seen a wooden box like Randy has. It looks like a special kit.

BTW, my extra 30-06 chamber is available for trade if anyone is interested. No box, just a loose loaded chamber.


As I was digging through my accumulation of subcalibers and the like, I spotted these three Zip chambers. The two with the knurl rings are marked
"ZIP PAT PENDING" and the other “ZIP 300 PATD…” The marking is quite faint.
Both blanks have the “U” headstamp.
Were ZIPs made in any other calibers???


Lew, left to right looks like you have a 30-06 and and 30-40 first type and a second type 300 Savage. Have found the markings are very inconsistant almost like each machinist sort of did his own thing. Are the internal blank chambers straight or necked? That seems to be another arbitrary thing about the chambers. Have never seen a chamber box marked as to the type blank cartridge it was made for or a box of cartridges marked as to the type of blank. Guess the buyer had to look before purchasing a box of cartridges to be sure they were the correct ones for his chambers. Will send you an email of some of my chamber boxes.


The 300 Savage has a necked blank and the 30-40 Krag has a straight blank.

Thanks for the email!!!