Ammo Project - Looking to Manufacture Replica 20mm Vulcan

I’m working for a company that produces replica ammunition and we’ve received a request to manufacture a 20mm Vulcan (like the type fired from an American A-10 Thunderbolt)

We’d like to manufacture it - just for the sheer intrigue of producing such an awesome cartridge but are having trouble with the initial design - especially in finding the accurate dimensions for the 20mm - measurements like rim thickness, shoulder length, shoulder diameter and overall weight.

Now that we’ve got the ball rolling on the 20mm we’re eyeing the next logical step - the 30mm. Again any help with regards dimensions or (ideally schematics) would be greatly appreciated!

The 20mm Vulcan was used in the F-series of fighters, and not the A-10 Thunderbolt. The only gun the A-10 has is the 30mm GAU-8 Avenger cannon.
This shows the size differences in the two. The 20mm Vulcan second from the right, and the 30mm Avenger on the far right.

Case dimensions measured from the rounds in my collection are:

Neck Diameter: 1.260"
Shoulder Diameter: 1.590"
Base Diameter: 1.720"
Rim Diameter: 1.730"
Case Length: 6.80"
Cartridge Length: 11.40"


Those are the dimensions for the 30mm, not the 20mm Vulcan. Right??


The green and orange projectiled rounds are for the 20MM Phalanx based CIWS used as an anti-missile defense onboard assorted US Navy warships. These were manufactured by Kilgore Industries in Toone,TN. Actually, not sure if they are the manufacturer of all the components, but they are assembled and tested there. The projectiles consist of a plastic sabot mated(press fitted) to an aluminum base, and contains a 12MM X 42MM tungsten core.

Here is my attempt at measurements (in MM):

Let me know if you need anymore dimensions. The green one weighs about 7.5 ounces. No primer or powder, so I’d add another couple of ounces.
Hope this helps.

PS The yellow and blue rounds would be for other than Phalanx use, I suppose. Case dimensions are the same. Projectile dimensions near so, with a tad different profile. And no fluting. The dotted lines denote the v-shaped flutes cuts.

[quote=“Ray Meketa”]IHMSA

Those are the dimensions for the 30mm, not the 20mm Vulcan. Right??


Yes Ray, that is correct.

Who do you work for, and what kinds of othe rreplica cartridges have you made? Just curious. Are they for collectors?

John Moss

Thanks all for the extremely helpful responses - many of which go way above the call of duty! From the blueprint slick rick uploaded we have a great starting point for the design team to work from and with any luck we’ll have a prototype replica later this month.

Leading on from the overall dimensions, one other item that would be very beneficial to us is info on the size and type of the primer used and if at all possible a picture of same.

Also - I know that many of the more “heavyweight” cartridges are screw in as opposed to press fit - Is this the case for the 20mm?

Thanks again

(Btw, my apologies for not getting back to this thread sooner - I returned to Ireland for the holidays and while it’s not quite in the dark ages, broadband can unfortunately be difficult to come by)

And just to answer John Ross’ question - I work for Technoframes (for anybody that might be interested the url is

We’re primarily an ammunition showcase manufacturer but have begun to diversify into developing Replica Ammunition. We’re new in this industry and up to today our largest replica in production is the 50 BMG - the 20mm Vulcan is a step up but we’ll give it a shot nonetheless.

With regard to who they’re for - like I mentioned in an earlier post, we manufacture for anyone that is interested in having the cartridges - Of course collectors have an inherent interest in cartriges and so are more likely to be interested in Replica’s but you might be surprised who else takes interest.

We attended the Arms & Hunting exhibition in Moscow late last year and found overwhelming demand for a wide range of calibers, just from people that wanted to display the cartridge or even just to have as a souveneir.

Hopefully I’m thinking of the “correct” 20mm.
Sorry about the low grade photo of the 20x102 primer (far right), but the photos are part of a comparitive set, not a detail set. That’s a 50BMG on the left.
IIRC the primer is a press in electric detonation type (as opposed to a percussive type).

Side view of the above lineup

In a lot of good books about cartridges ,you can find many drawings with the dimensions and other info…
In a lot of different calibers.

ps when you need info about this books I can help you…

Isn’t technoframe an italian factory?

Is the third round in your picture a 408 Cheytac?


Is the third round in your picture a 408 Cheytac?


Pivi…that is a .50 Browning Machine Gun cartridge, custom loaded with a Hornady 750 grain A-Max bullet with aluminum nose. These are used for 1000-yard benchrest matches with custom bolt-action rifles.


left to right
12,7x99 (.50
.416 Barrett
.408 Chey Tec

.408 Chey Tec

I have a 408 cheytac sample (only a new unprimed case) and that round in the picture has a bullet similar to those that I have seen in some 408 cheytac pictures:very pointed


Yes,lookin the picture better the third cartridge is certainly a 50 bmg.The custom bullet fooled me…


gyrojet - we have some books already but they deal primarily with handgun and rifle calibers. I’ll take you up on your offer re info on the books though! I’m going to be taking in the Shot Show in February so it’d be great if you could let me know if there’s a US wide bookshop chain that might stock it so I can pick a copy up while in Vegas…

at this stage we’ve gathered more than enough specifications and diagramatic material (thanks to everyone who contributed) and have already started sourcing materials for production - A site we found very useful was, which is really comprehensive on ammo (big drawback was that it’s entirely in Spanish)

We hope to have the first prototype later this month / early Feb and I’ll post a few pics of how it turns our up on this thread when it comes to hand.

Go here to translate a word, sentence or the entire web site from Spanish to English. It mangles some technical words but does a fairly good job.