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Posted: 12/17/2002 1:16:38 PM EDT
I can't seem to find much about this bigass cartridge. All I know is that it fits lotsa powder, has electrical contact points at the rear, and The Man fears my owning a 20mm rifle.

I think it would be neat to build up a project rifle though, wildcatted to fifty caliber for legality.

So who makes 20mm actions? Can 20mm cartridges be resized like brass of our usual ammo?
Link Posted: 12/17/2002 2:39:20 PM EDT
Link Posted: 12/17/2002 2:48:11 PM EDT
Okay I forgot to say, i want to build a bolt-action.
Link Posted: 12/17/2002 2:54:40 PM EDT
DOH...!
Link Posted: 12/17/2002 3:44:41 PM EDT
If I recall, it is GE. I seem to remember the GE tag on The B52-H
Link Posted: 12/17/2002 4:48:24 PM EDT
Most of the 20MM M-61 cases I've seen were either aluminimum, or steel. For brass cases you'd have to use the 20X139MM. Not cheap, as people who own Lahtis, and SI-1000's want these casings as well.

As to an action? No idea. A heavily scaled up .50 design might work.

Meplat-
Link Posted: 12/17/2002 5:05:29 PM EDT
IRC vulcan ammo is electry primed.

and u could keep it 20mm if u registered it under the NFA as a Destructive Device.
Link Posted: 12/17/2002 5:45:34 PM EDT
I have heard of .50 shooters necking 20mm cases to .50, better ballistics/range I think he said.
Link Posted: 12/17/2002 6:19:13 PM EDT
SBR711 that's exactly what I want to do.
Link Posted: 12/17/2002 7:21:02 PM EDT
Wow...In general that's all I have to say about this thread.

What kind of velocities would you get out of a 20mm casing necked down to 50cal? Can you imagine how fast you would get if you used one of those .50 cal .308 sabots in that loadout!!!

Link Posted: 12/17/2002 8:45:39 PM EDT
necked? have you guys seen the difference in sizes between these two cartridges? I think you're confused.
Link Posted: 12/17/2002 9:47:25 PM EDT
there is no "necking down" a 20mm case HAHAHA but if you are seriously interested in building this i have devised a simulation. first locate a live hand grenade. (although illegal it should still be easier than finding 20mm ammo) now pinch said grenade between your head and shoulder just like momma used to do with the phone when she was neglecting you. pull pin...wait 3-5 seconds for the "sound of freedom"


like an aimpoint on a mosin-nagant or a fully sporterized Carcano...why?
Link Posted: 12/17/2002 10:11:16 PM EDT
1) 20mm Vulcan (and yes, it's electrically fired (like that special electric Remmington rifle), so you'd need a different case design) isn't the only 20mm round out there... The South Africans and Russians both field 20mm rifles (think Barrett in 20mm). I discovered this when I stumbled onto a discussion where Canadian gun owners were talking about the fact that they can't own .50BMG weapons, however 20mm is legal (odd...). One of them claimed to own a 20mm rifle, and so on...

2) Not only would a true 20mm rifle be a DD, each round of ammo would be a DD, and you couldn't legally reload them without a DD manufacturerer's license.
Link Posted: 12/17/2002 11:19:07 PM EDT
Can you buy a newly manufactured Destructive Device?

Like a brand new HK grenade launcher or something if they would sell it to you and you registered it....
Link Posted: 12/18/2002 12:58:04 AM EDT

Originally Posted By Dave_A:
2) Not only would a true 20mm rifle be a DD, each round of ammo would be a DD, and you couldn't legally reload them without a DD manufacturerer's license.



Certain rounds are DD, others are not. Training rounds are NOT DD and could be shot, if you had a RRDD in 20mm.

Serbu has been talking about making one. He also is selling usable training rounds.
Link Posted: 12/18/2002 1:24:08 AM EDT

Originally Posted By Dave_A:
2) Not only would a true 20mm rifle be a DD, each round of ammo would be a DD, and you couldn't legally reload them without a DD manufacturerer's license.



Nope, only HE rounds are DD's. non-explosive(less than 0.5oz? of explosive) are not DD's. The 40MM grenade guys play with "training" rounds that don't go BOOM when they land so they don't have to go DD on the ammo.
Link Posted: 12/18/2002 3:51:56 AM EDT
http://www.full-auto.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=28;t=000009
Link Posted: 12/18/2002 4:46:39 AM EDT
http://www.quarry.nildram.co.uk/MilRel.htm

Has some nice info with pics. Does not seem like such a stretch to neck the case of the 20mm cartridge to the .50.
Link Posted: 12/18/2002 5:28:12 AM EDT
[Last Edit: 12/18/2002 5:29:58 AM EDT by SBR7_11]
Link Posted: 12/18/2002 5:40:21 AM EDT
I saw a Barrett 25mm version of the M82 on the web the other day. That might be the correct platform.
Link Posted: 12/18/2002 12:58:36 PM EDT

Originally Posted By Jack_Of_Some_Trades:

Originally Posted By Dave_A:
2) Not only would a true 20mm rifle be a DD, each round of ammo would be a DD, and you couldn't legally reload them without a DD manufacturerer's license.



Nope, only HE rounds are DD's. non-explosive(less than 0.5oz? of explosive) are not DD's. The 40MM grenade guys play with "training" rounds that don't go BOOM when they land so they don't have to go DD on the ammo.



Actually, any firearm with a bore larger than 50 cal is a DD, as is it's ammo (except 'sporting' shotguns).

20mm is bigger than 50cal, so it fits the DD category...
Link Posted: 12/18/2002 10:29:43 PM EDT
The American M61 and M39 cannon fire a 20x102mm cartridge, with a rim diameter of 29.5mm. This cartridge actually started life as a WW2 .60" anti-tank rifle round (the gun was never adopted). During WW2, the cartridge was also used in an experimental US aircraft gun, and the tests included necking it down to .50 cal. The .50/60 was capable of firing a 42.8g bullet at 1,200 m/s or a 32.4g one at 1,340 m/s (that's 660 grains at 3,940 fps or 500 grains at 4,400 fps). After the war, the case was necked up to 20mm. There is a photo of all three cartridges on my website; see the article on 'Military Cartridge Relationships'.

The USA also necked down the 20x110 Hispano round to .50 cal in WW2; there's a photo of that in the same article.

Other 20mm currently in service include the 20x128 Oerlikon KAA, the 20x139 Oerlikon KAD/HS 820 (not the same as the 20x138B used in the WW2 Lahti and Solothurn S18-1000 anti-tank rifles), and the 20x82 in the South African Vektor GA-1 MG (the venerable MG 151/20, still being made).

Rifles currently offered in 20mm include the South African Mechem NTW (available in 20x82 or the 14.5x114 Russian KPV round), the Finnish Helenius APH RK97 in 20x99R (the WW2 Soviet ShVAK aircraft cannon round) and the Croatian RT20 AMR, in 20x110 Hispano. Take your pick, and insure your collarbone :)

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/
Link Posted: 12/18/2002 11:18:00 PM EDT
[Last Edit: 12/18/2002 11:18:36 PM EDT by Skammy]

Originally Posted By SBR7_11:
I have heard of .50 shooters necking 20mm cases to .50, better ballistics/range I think he said.




Link Posted: 12/18/2002 11:57:54 PM EDT

Originally Posted By Dave_A:
Actually, any firearm with a bore larger than 50 cal is a DD, as is it's ammo (except 'sporting' shotguns).

20mm is bigger than 50cal, so it fits the DD category...



I will say it again, some ammo larger than .50 cal is DD other is not.

Share with us where the law says any ammo larger than .50cal is DD. I am always willing to be educated.
Link Posted: 12/19/2002 12:05:18 AM EDT
I cant seem to find any info on the GE mini gun on thier website.
Link Posted: 12/19/2002 12:30:42 AM EDT
[Last Edit: 12/19/2002 12:54:22 AM EDT by TwoStage]
Ok, here it is.

I guess I can still rember some things.

General Elec. M61A1 Vulcan 20mm Cannon
www.wpafb.af.mil/museum/arm/arm8.htm

Here is a sound track of one firing.
usmilitary.about.com/library/milinfo/milsounds/blvulcan.htm


Had to fix the links, they are good now
Link Posted: 12/19/2002 6:00:35 AM EDT

Originally Posted By sesat_ram:
I think it would be neat to build up a project rifle though, wildcatted to fifty caliber for legality.



Already done by McMillan. Called the .50 FatMac. It's a 20mm, slightly shortened and necked down to .50.
Link Posted: 12/19/2002 11:28:10 AM EDT

Originally Posted By brouhaha:
Already done by McMillan. Called the .50 FatMac. It's a 20mm, slightly shortened and necked down to .50.



I've seen one of those cartridges. It's considerably shortenend, to only about half the length. The object wasn't to improve velocity over the .50, IIRC, but to get the same performance from a much shorter round, better suited to compact self-loading guns.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/
Link Posted: 12/19/2002 11:34:52 AM EDT

Originally Posted By Dave_A:
]

Actually, any firearm with a bore larger than 50 cal is a DD, as is it's ammo (except 'sporting' shotguns).




Sooo, 54cal blackpower rifles are DD and so are 54cal balls?
Link Posted: 12/19/2002 12:20:57 PM EDT
General Electric doesn't make the 20mm Vulcan any more. That division was sold to General Dynamics. BTW, current US 20MM M50 series and PGU-27, -28, and -30 ammo is brass cased. I've only seen a few older lots of 20mm (in USAF use) that were steel cased.
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