20mm Dummy Round, Need Info Please

[zero_chances]

So I have come accross this 20mm INERT cartridge, and i was wondering if any of you guys could give me some background info on it. The headstamp reads - 20mm- MK5. MOD.0 --- RNO 12 . 63. And on the actual bullet it says 20mm DUmmy round for gun MK 12 MK 103 MOD 0. Thats pretty much all I know about it.

Also, I beleive that it has powder in it. I can hear it when I shake it.


And here is a picture of it

 

[SDC]

It looks to be the current standard 20mm case shape (same as used in the F-18 and the M61 Vulcan), but the "MK-Mod" nomenclature means that it was originally a Navy item. It would've been packed with an inert filler to make sure that it weighs the same as a live round (which is important when it comes to testing the feed system and automated loading/unloading machines).
Edit to add: the "12.63" notation shows that this round was produced in December of 1963.

 

[zero_chances]

Thanks Thats pretty much everything I was trying to find out.

One more thing, what where these massive cartridges shot out of? I am guessing a plane? Helicopter?

Thanks again

 

[Donut]

Anything equipped with an M61A1 Vulcan cannon.

http://en.wikipedia.org/wiki/M61_Vulcan

 

[hso]

Would one of the members with professional experience with this ammunition please let us know if this inert round has no powder and no primer.

Accidents involving 40mm grenades that were thought to be safe in the past couple of years should make all of us cautious about any ammunition found in the field and brought home as souvineers.

 

[Delmar]

Although the Navy may use different ammunition coding systems than the Army, my MOS was a 16R, Vulcan crewman. I was on both the self propelled M163 (M113 with the vulcan) and the towed M167. That round looks like a TPT or Target Practice Tracer, given the blue color of the projectile.

If it is "inert", there should be a hole where the primer should be. The inert rounds we were issued to time the feeder and drum was not a standard case, and no hole was drilled in the base for a primer.

If there is a primer on this particular round, I'd be very careful. Vulcan ammunition is fired electically, so there is that chance that static electricity could fire the round.

 

[SDC]

The blue colour is common to most non-explosive projectiles, even those that are never meant to be fired (ie. on a dummy round). If this was a live tracer, you'd also see an orange line of "T-T-T-T"s around the body of the projectile. I've seen these dummies made with both NO primers/primer pockets (just a solid case head), or the opposite.

 

[Gifted]

None of the ones we used for functional checks lacked a primer. They put in an inert insert in there so you could do the electrical functional check with a multimeter. You cycle the gun to where the firign pin hits, and check that it's grounding, then cycle it past, and make sure it's not.

The PGU rounds for the GAU-8 had plastic inserts instead of primers. That obviously doesn't work for checking the operation of an electrically primed gun.

 

[Tbu61]

Correct me if I'm wrong, but it may be filled with Sand to closely approximate the weight of a live round.

They use these dummies when the gun is Test Cycled to verify mechanical timing and adjustments. If the dummy round were a different weight, (than live ammo) it would behave differently in the entire gun mechanism .

If you ever saw a Vulcan fire you would get the idea rather quickly, it's powered electrically and really moves those shells in the feed belt and drum!

 

[zero_chances]

I think Gifted is right on this one, cause it has something in the back that looks like a primer, but it says INERT on the casing and on the projectile. There is no line of T's on it, so i think that rules out it being a tracer.

And i just found that RNO 1.157 is written on the casing in very faint lettering.


Any, I beleive I found a nice interesting peice for about 5 dollars

 

[FIFTYGUY]

*NOT* Vulcan - close but no cigar

Zero Chance said:

So I have come accross this 20mm INERT cartridge, and i was headstamp reads - 20mm- MK5. MOD.0 --- RNO 12 . 63. And on the actual wondering if any of you guys could give me some background info on it. The
bullet it says 20mm DUmmy round for gun MK 12 MK 103 MOD 0

And everybody decided it was Vulcan. Including you guys who have worked on Vulcan guns in the military...

This is actually a pretty common mistake. The round Zero Chance has is known as the "20x110mm US Navy", a.k.a. the "Mk 100" series of ammunition. Essentially the same as Vulcan, except the case is about 5/8" longer, the projo is a little longer and heavier. Obviously it won't interchange with the 20x102mm Vulcan.

Bit of history:

During and after WWII a huge amount of automatic weapons R&D went on in this country. One big push was for a better aircraft cannon. With the rapid development of jets, cannon were needed that had a high enough rate of fire, with fast enough projectiles to give the gunner a chance to actually hit another plane in a dogfight. Everything under the sun was eventually tried.

The WWII-standard 20x110mm Hispano-Suiza round (no relation to the Mk 100 ammo) was long-known to be less than ideal. The 20x110mm RB Oerlikon round (again, no relation to the Mk 100) was even worse, but the US Navy had tried to get Melvin Johnson to develop a belt-fed aircraft cannon using the stuff. Johnson complained bitterly, but that's what they wanted (see Chinn's Vol III, pg. 290). Eventually they let him use the standard 20mm Hispano...

Since Hispano performance was maxed-out, there were attempts to get faster-firing guns with more muzzle velocity by necking down various 20mm cases to 15mm (.60 caliber) and even to take .50 BMG projos. None of these worked very well. In fact it was noted that better ballistics were obtained with .60 caliber bullets from the standard .60 Cal cartridge than from necked-down 20mm Hispano casings!

This must have raised the possibility of better ballistics from necking-UP the .60 Cal to 20mm. This was quite successful, and became the 20x110mm US Navy cartridge. The Navy used this round in only two guns: the Mk 11 (Mod 1 and later, although the Marquardt rimless ammo used in the Mod 0 was essentially the same case profile, albeit with special projos), and the Mk 12. The Mk 11 was a fantastic thing, but too complicated and ahead of its time. It was only used in an external gun pod. The Mk 12 was a tweaked evolution of the basic Hispano-Suiza aircraft gun, and was well-known for paired installation in A4 Skyhawks.

The Army did the same thing, except they wanted a more compact round. So they ended up with the 20x102mm Vulcan. This logistical silliness of maintaining two separate designs of 20mm ammo went on until 1968, when the Vulcan officially became the Tri-Service 20mm round.

Interestingly, Vulcan is almost always brass-cased, whereas Mk 100 ammo is almost always steel cased. The ramming forces from the Navy's reciprocating guns (especially the Mk 11, which until Mod 3 literally *shot* the ammo into the chamber!) put a beating on their ammo, so they went with steel casings. The Army was using Vulcan Gatlings for air defense, which gradually chambered and extracted the cases. Presumably they had more need for corrosion resistance, and less for weight savings...

I've never seen a headstamp on Vulcan ammo. Mk 100 however is profusely marked (info roll-stamped on projo rotating bands, headstamps, etc.). Zero Chances' round is obviously a dummy (Mk 103). I believe the Mk 5 designation is for the casing, as this is headstamped on other non-dummy Mk 100 rounds in my collection. This is pretty common practice with artillery ammo, where the case is marked for its type, the projo as to its type, and then the round itself as to _its_ overall type. My earlier Mk 103 dummy round has no "Mk" number on the (brown) projo, but both my later Mk 103 Mod 1 dummy rounds ID their (yellow) projos as "Mk 11" on the rotating band. The Mod 1's have no primer.

The stuff you hear when you shake it is certainly sand or some such filler to give accurate handling characteristics.

The "RNO" means it was made by Amron, a prolific US manufacturer of medium-caliber cannon casings. You'll also see their initials on 20mm "Vulcan", 25mm "Bushmaster", and 30mm "Avenger" ammo as well.

I know a guy with a Mk12 cannon. SARCO is selling a feeder/delinker for one right now. Lomont has had a couple of live ones for sale, including the short-barrelled turret version (Mod 1, see Chinn's Vol III pg. 410). I have a copy of the Mk 12 manual, although Chinn pretty much reproduced it "in toto" in his books. Indiana surplus has some demilled Mk 11 cannon for sale.

I also use a Mk 12 Skyhawk muzzle brake on my 20mm Vulcan rifle:

http://members.aol.com/fiftyguy/ptrd20mm.htm

Oh, and some more history:

The ".60 Cal" was initially an anti-tank rifle round, almost identical to the 14.5x114mm Russian round. Quite a few eerie similarities between those two calibers. The US AT-rifle project (T1E1) was quickly dropped, but the round was resurrected for aircraft cannon use. Many experimental guns were developed (T130 series and others), and over six million rounds of ammo were made during WWII, but no guns were ever adopted.

The .60 Cal itself was designed by increasing each dimension of the .50 BMG by 20%. The .50 was itself (in final form) a scaled-up .30-06.

 

[Archie]

Fifty Guy...

Thanks. I appreciate knowing this sort of stuff. Finding out where 'stuff' came from is always interesting.

 

[zero_chances]

That was one heck of an informational post! Thanks alot . Its amazing how much history this little thing has.

BTW, that is an interesting rifle you have got there What kinda recoil does that thing put out?!?!

Thanks again

 

[Wild Weasel]

To complete another reply. The M61 Vulcan was not only fired electically but also with hydralic power. The F-105 has a Vulcan in the nose and was loaded by turning the gun with a drive system that was powered somewhat like a chain saw. We installed the dummy round into the system before loading and cycled the complete system running the round completely thru the drum. When the dummy was ejected out the other end, the system was completely loaded.

I presume that there were many different ways that dummys were made. Ours were silver colored with a band that said 20mm dummy and the primer hole had a staked plug installed.

Spent 2 tours as a weapons load crew chief on the F-105F and G model Wild Weasels. Love that Vulcan..

 

[One of Many]

I have a 20mm inert round, with a brass case that carries NO Headstamp. The case is roll marked (ink) with:

20MM M103
ACN
92B007-144

The projectile is color coded with a narrow RED band nearest the tip, followed by a broad YELLOW band, then followed by a narrow BLACK band nearest the crimp of the case. The black band is lettered with WHITE letters:

WM-92B009-032 20MM

The primer pocket is empty, and drilled, so that a paper clip can be inserted all of the way to the base of the projectile.

This round has been marked with a handwritten permanent ink on both the case and the projectile, with the word INERT.

I received this as a gift for working on a project that did visual inspection of ordnance using digital cameras and image analysis software, to allow a robotic system to manipulate the rounds into a test station (this allowed the system operator to control the process remotely for safety purposes - you don't want to have toxic materials leaking around test operators).

I was never told what this round was used in; it is a neat conversation starter.

 

[FIFTYGUY]

One of Many says:

I have a 20mm inert round, with a brass case that carries NO Headstamp. The case is roll marked (ink) with:

20MM M103
ACN
92B007-144

Now *that's* a Vulcan round. M103 is the case designation (although Vulcan is commonly known as "M50" series ammo, from the original M5x family of rounds in this caliber).

"ACN" is another Amron code, for their Antigo, WI plant. I've got this code on some 40x53SR automatic grenade launcher casings as well...

The projectile is color coded with a narrow RED band nearest the tip, followed by a broad YELLOW band, then followed by a narrow BLACK band nearest the crimp of the case. The black band is lettered with WHITE letters:

WM-92B009-032 20MM

Almost certainly a M56[Ax] HEI (High-Explosive Incendiary) projo.

WM is the projo manufacturer's code (I dunno who, but it's on other Vulcan projos in my collection). Pretty sure "92" is the year of manufacture (does this jive with the date of your acquisition?)

There are a lot of grungy HEI projos out there. Heck, I reload with surplus inert ones - no advantage over blue M55 TP projos for plinking, except you can unscrew the inert fuze and fill them with whatever you wish. Nice projos with good clean original paint and markings are much rarer, especially in the HEI flavor.

As "Vulcan", this round was capable of being used in a variety of guns. In the US alone, it was used in the M39 family of revolver cannon; the M61 or M168 six-barrelled Gatling ("Vulcan") as an aircraft and anti-aircraft cannon; the Naval Phalanx Close-In Weapon System for missile defense; the M197 three-barrelled Gatling used in the nose turret of the Bell AH-1J and the AH-1W SuperCobra helicopters; the updated XM-301 for the RAH-66 Comanche; the M195 six-barrelled short-barrelled Gatling on the wings of the AH-1G Cobra helicopter; the GAU-4/A self(gas)-powered six-barrelled Gatling used in the SUU-23/A gun pod. Also in the GE 120B gun, the Navy's Mk 22 project, and some foreign guns as well.

 

[Autolite]

Years ago I was an M61A1 mechanic. Based on the information you've provided I am fairly certain that you've got a LIVE ROUND!!! The "INERT" stamp applies to the projectile only meaning that it is a target practice (non-explosive-blue) projectile. The round itself is live! If you can shake it and hear the powder charge then it is most certainly live. They do not "fill the case with sand" to create ballast. A "ballast" round looks completely different. Ballast rounds are all orange in colour and quite obviously fake (Ballast=Orange, Dummy=Silver). Check the primer. If there is a blue inner ring around the primer then it is electrically fired. (AFAIK the Navy doesn't like to use electric primer ammunition if there is an alternative). A red inner ring around the primer means that it is percussion fired. In any case I would suggest that you get rid of it somehow. Drop it in an amnesty box somewhere or hand it over to the military for disposal. If it is an electrically primed 20mm round, it can be set off just buy a static discharge from your own body. It's not worth keeping it around. It's a dangerous souvenir ...

 

[Autolite]

This is the head of a fired 20mm electrically primed Vulcan round. The cute dimple on the primer is caused by the fired primer expanding against the firing pin. This is what an expended primer should look like. If there is still powder in the case then you've still got a problem ...

 

[FIFTYGUY]

Years ago I was an M61A1 mechanic. Based on the information you've
provided I am fairly certain that you've got a LIVE ROUND!!! The "INERT"
stamp applies to the projectile only meaning that it is a target practice (non-
explosive-blue) projectile. The round itself is live!

All the items marked "INERT" in my collection, especially military-marked dummies, are in fact totally inert. This includes fuzes, projos, submunitions, and ammo. If the round is loaded with an inert projo, this is specified by the marking ("Loaded With Inert Projectile") or the inert component is marked as such.

On the other hand, I've never seen a live Target-Practice round with the case marked as "Inert". Normal, live, TP ammo is never marked "Inert" anyhwere.

If you can shake it and hear the powder charge then it is most certainly live. They do not "fill the case with sand" to create ballast.

In the 30mm M848 dummy round "Primer and propellant are replaced with threaded steel bolt attached to the base of the projectile body to maintain same weight and balance as the TP cartridge".

In the 25mm M794 dummy round "The cartridge case cavity is filled through an enlarged primer hole with epoxy resin filler to approximate the weight of the M792 high explosive incendiary-tracer and M793 TP-T service cartridges."

The above from the Army ammunition data sheets, TM-43-0001-27, April 1994.

I even have a Army drawing, cutaway pic of the M51 Vulcan dummy. According to drawing RA PD 212989A, the M51 dummy has a solid case head with no primer pocket (this is actually the "Cartridge Case, M103 Dummy", same M-number as the "live" case). Headstamp is an ink marking "INERT", and the case is filled with "INERT MATERIAL".

From "Airmunitions, General" (Air Force T.O. 11A-1-20, Feb 1966):

"CARTRIDGE, 20-MM, DUMMY, M51. This cartridge (figure 10-1) is a completely inert assembly that is used for drill purposes, for testing the feeder assembly of the weapon, and for ballast [!!!]. The service cartridge is simulated by assembling the projectile of ball cartridge M55 or M55A1 with steel cartridge case M103 (dummy). The cartridge case contains approximately .086 pound of inert material to produce an average overall weight equal to that of the service cartridge."

In larger arty it's common practice to inert-fill shells for various tests. 50/50 water-antifreeze is commonly used as a weight substitute for nerve agents.

"Some target-practice projectiles are cast iron while others are service projectiles loaded with sand or other inert material." ... "Dummy propelling charges are filled with wood grains simulating 'live' propellant grains, and the color of the cloth in dummy propelling charge bags simulates that used in 'live' propelling charge bags." (from "Ammunition, General, TM 9-1900, June 1956).

In "History of Modern U.S. Military Small Arms Ammunition, Volume II", Hackley and Woodin wrote that "Numerous other types of [.60 Cal] inert rounds were assembled for demonstration and other purposes and may be found with a variety of components. Some have been examined loaded with inert charges." They also mention that .50 BMG dummies have been made with inert powder charges: "One round headstamped F A 45 has a blackened primer and an inert powder charge and is marked INERT in black ink on the case." And: "Specially weighted dummy cartridges were used at Frankford Arsenal to verify the accuracy of gage and weigh machines and inspection equipment."

I can't recall where, but I have read of the use of pencil lead as a inert filler substitute for propellant. Problem with that is, it must *look* just like real powder (good idea if you're making a cutaway display, though!).

A "ballast" round looks completely different. Ballast rounds are all orange in colour and quite obviously fake (Ballast=Orange, Dummy=Silver).

I have a M254 Vulcan dummy which is all white plastic. Never seen an orange one, although other countries have made dummies in all colors of plastic. Seems like a good idea! The plastic was introduced because it reduced the wear and tear on the gun and feeder, not to simulate the weight of the service rounds (which they don't).

I have two M51 Vulcan dummies of the "all-silver" type, although I read they are supposed to start off with a chromate finish (it must wear off). One of them has some kind of loose inert filler, by the sound of it more like lead or steel shot!

Check the primer. If there is a blue inner ring around the primer then it is electrically fired.

That's really no indication. I've got a dummy .60 Cal round with what appears to be a perfectly intact unfired electric primer, but it's a dummy (ink-marked INERT and no powder inside).

(AFAIK the Navy doesn't like to use electric primer ammunition if there is an alternative).

Funny that they keep using it... yes, it has its idiosyncrasies but it works.

Although they did come out with the MK 7 link, with the protective tab to cover the primer. I think more to block radio transmitters and radar from setting off the primer, though!

A red inner ring around the primer means that it is percussion fired.

Um, no. It means they used a different color plastic that day. I have live examples of both. I've dissassembled hundreds of electric primers in the course of reloading ammo...

If there's *any* inner ring with an insulator, it's electric-primed.

In any case I would suggest that you get rid of it somehow. Drop it in an amnesty box somewhere or hand it over to the military for disposal.

Or just mail it to me. I'll pay the shipping and throw in $10 for your trouble.

If it is an electrically primed 20mm round, it can be set off just buy a static discharge from your own body.

IF it's got a live primer. I've heard this anecdotal evidence before. And as a M61 tech, you'd certainly be in a position to know! But have you ever directly *seen* evidence that this *has* ever happened? I personally count it as a remote possibility. It takes about 400 volts (trivial static charge) at a good amount of current to light that primer off. Common sense dictates that gluing a piece of 3/4" square of aluminum foil over the primer will prevent any problems.

It's not worth keeping it around. It's a dangerous souvenir ...

Do you really think they'd hand out LIVE HEI rounds to project team members as mementos? Anyhow, modern fuzes are great. The live HEI fuzes require both spin- and setback- arming.

There's really no way of telling with some stuff you come across. I've heard stories of things found on museum director's desks that were filled with 40-year-old live HE! Then you've got some of us active shooters running around making dummy rounds out of mix and match components.

Personally, if I make up a dummy round for function testing or as a gift, I make a point of drilling out the primer pocket so neither will a primer ever be able to be seated in it (prevents "squib loads") nor will it be able to hold powder without it running out the gaping primer hole.

 

[bamawrx]

I have a round that has no head stamp but says on the side 20MM M103 ACN 91H006-722

It has a blue projectile with the following marks:
20MM TP
M55A2
LC-911202-564
WM-91F009-047 M55A3B1

Purchased at gunshow. Is this a vulcan round?

 

[FIFTYGUY]

bamawrx wrote:

Purchased at gunshow. Is this a vulcan round?

Yes.

 

[bamawrx]

Its live, is that a problem?

 

[FIFTYGUY]

Its live, is that a problem?

I don't see why. It's a lot more useful as a live round.

 

[bamawrx]

Yes, it would be useful if I had a gun to fire it in. Inert rounds are not as interesting as the It Will Go Off variety. Just don't want it on my desk if its dangerous.

 

[Autolite]

"I've heard this anecdotal evidence before".

Me too! As a matter of fact, I read it under the handling precautions for electrically primed ammunition in the applicable technical orders. Nasty old federal government for publishing such bogus information ...