Heavy Ordnance

[Patriot]

This Thread used to be the .50BMG vs. 20mm thread, but I've changed the title to discuss all things "heavy metal." Tanks, artillery, military aircraft, warships, or any of the ordnance they use is up for discussion here. Small arms and calibers are fair topics also.

EDIT: 8-24-09
Posts 1 and 2 have been reversed so that the index appears up to. This post was originally the post #2



Index page covering the main topics by page.



Page1
.50 cal, 20mm, M1 Garands

Page 2
Tank armor, M1 Garands, Phalanx (CIWS), Battleships

Page 3
Battleships, Railroad guns, 16" guns

Page 4
16"guns, APC's, Railroad guns, Apache Helicopter, AR-15 and 8x56R talk, M1 Garands, Small caliber talk.

Page 5
Small caliber talk.


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[Patriot]

Re: .50BMG vs. 20mm

This Thread used to be the .50BMG vs. 20mm thread, but I've changed the title to discuss all things "heavy metal." Tanks, artillery, military aircraft, warships, or any of the ordnance they use is up for discussion here.

EDIT: 8-24-09
Posts 1 and 2 have been reversed so that the index appears up to. This post was originally the first.





Old vs. New Aircraft Armament

I'm not sure how many people will find this interesting but I know we have firearm enthusiasts here and probably a few airplane and technology buffs too.

I happened to be reading up on WWII aircraft, as anything associated with military hardware is one of my past times. Aircraft, tanks, artillery, ships, are all fair game. I happened to look up at my book shelf at an assortment of ammunition sitting up there and I wanted to better understand the advantages of a single Gatling-style aircraft gun as compared to multiple, single barrel, heavy machineguns, like the systems used in WWII and Korean era aircraft.

Having fired at least a thousand rounds from the M2 heavy machine gun I'm always impressed with the energy it's able to deliver down range. 50BMG can crack and zip through engine blocks, crush brick and granite and chews down stacks of sand bags like no other small arm can. It's almost funny that it's considered a "small arm" as it's really in a whole different category from anything else I've experience in portable full-autos weapons or even larger tripod fired machine guns like the Vickers, Browning .30, or MG42. I'm amazed to think of the firepower when 6 or 8 forward firing M2s were combined in aircraft to concentrate their firepower onto one spot. Having said that I've got to think the GE M61 type Vulcan must be one heck of a weapon system that it could replace 8 M2s firing at 800+ rounds (non boosted) per minute each.

I wanted to see if I could put to paper some calculations to help me see the differences more clearly and that's mainly all this thread is about.


Lets start with the specifications of each gun type.

Browning M2 Heavy Machine Gun. (AN/M2 for our example)
Recoil operated. (short recoil technically)
Air-cooled
.50 MBG
750-850 rounds per minute (non-boosted)
84 lbs

http://www.fas.org/man/dod-101/sys/land/m2-50cal.htm
http://en.wikipedia.org/wiki/Browning_M2



General Dynamics M61A2 Vulcan (Previously a General Electric product)
Pneumatically or hydraulically operated
Six-barreled, air-cooled
20mm PGU-28
4000-6600 rounds per minute selectable
202 lbs (A2)

http://www.fas.org/man/dod-101/sys/ac/equip/m61.htm
http://en.wikipedia.org/wiki/M61_Vulcan
http://www.youtube.com/watch?v=Gn9Lp...eature=related





A look at each cartridge.

.50 BMG
622 grain API round (frequently used at that time in fighter aircraft)
2910 feet per second muzzle velocity


20mm PGU-28B (previously the M50 series)
1543 grain (3.5oz) (100gram) semi-armor (soft core) piecing high explosive incendiary
3450 feet per second muzzle velocity



The two rounds (this particular 20mm is of the 50 series not the low-drag PGU) very close to actual size.

…and another which you flashlight folks can relate to. (very close to actual size)
Left to right, CR123, .223, .308, .300WM, .50BMG, 20mm

A look at each aircraft:

I wanted to use the P-47 Thunderbolt because it was one of the most heavily armed fighter aircraft of its day with 8 x .50cal M2s, four in each wing
http://en.wikipedia.org/wiki/P-47_Thunderbolt

I'll use the F22, and F18E since they both use the A2 variant of the gun. The A1 variant had more rotating mass and thus limited the gun to about 6000rpm. The A2 because of its lighter weight barrels has the side benefit of increasing the rate of fire to 6600rpm.
http://en.wikipedia.org/wiki/F22_Raptor



The math:

I'm going to keep this simple because I'm not very good with math and although I can calculate muzzle energy I'm not interested in doing that. Instead I'm going to use a "Power Factor" (PF) formula, which uses the weight in grains of a given projectile x its velocity in feet per second.

Now there are all sorts of different loads available for every caliber so you ballistics gurus can settle down if it looks like I've undercut the performance of your favorite cartridge…lol. Obviously hand loading certain calibers, especially in the case of rifles rounds will usually allow for more performance. I'm simply going to use some generalist examples for Power Factors of well-known small arms ammo to set the stage for the big boys.


Power factor charts (weight x velocity)

If the numbers seem to big, just abbreviate them by dropping what's behind the first decimal. As you can see, the 50BMG and 20mm rounds are in a class of their own.

.22 Long Rifle 46,000
9mm Luger 142,600
.40 S&W 180,000
.45APC 207,000
.357 Mag 221,000
.44 Mag 336,000

5.56 x 45 170,500
7.62 x 39 282,900
7.66 x 51 382,200
300 Win Mag 540,000

.50BMG 1,810,020
.20mm 5,326,350


In order to compare the relative performance of 8 x .50 caliber guns to the 20mm Vulcan we have to multiply the firing rate of a single gun x 8.

8 x M2
800 round per minute x 8 guns = 6400 rounds per minute

M61
A single M61A2 fires at 6600 rounds per minute



Now we multiply each gun's rate of fire x the energy of each individual round, but first we'll reduce the numbers since they become too large. We'll convert grains to lbs for that.

.50BMG
622grain x 2900fps = 1,810,020 (PF)
622 grain = .088 lbs
.088lbs x 2910fps = 256.08

.20mm
1543grain x 3450fps = 5,323,350 (PF)
1543 grain = .218lbs
.218lbs x 3450fps = 752.10 (roughly 3 times the energy of the .50BMG)


Conclusion:

Since 752.10 divided by 256.08 = 2.94, it's about right to say that the M61 produces 294% more gun energy than a P47 with 8 x .50cal M2s. In other words it would take 23.52 M2 machine guns to match the firepower of a single M61. This only applies to muzzle energy, since the more range increases the more the gap will grow between the two due to differences in retained energy.



Just for fun, let's look at the weight of projectiles leaving the aircraft. This of course doesn't factor in velocity, only projectile weight per second at each caliber's respective speed.

8 x .50BMG
6400 rpm divided by 60sec = 106.67 rounds per sec x .088 lbs = 9.39 lbs per second of projectiles

20mm
6600 rpm divided by 60sec = 110 rounds per sec x .218 lbs = 23.98 lbs per second of projectiles


[FONT=&quot]That's it for now. Later I'm going to compare the GAU-8 30mm gun, (the one the A-10 Thunderbolt II / Warthog) to the GAU-19 tri-barreled .50 caliber, which is rumored to replace the commander's M2 on a few M1A2 SEP tanks for testing. [/FONT]
__________________
-Patriot- "Government is not reason; it is not eloquence; it is force. Like fire, it is a dangerous servant and a fearful master." -George Washington-

 

[MarNav1]

Re: .50BMG vs. 20mm

No comparison.

 

[KC2IXE]

Re: .50BMG vs. 20mm

got to bring my .50 cal round home so I can take it's photo next to a GAU-8 round (I have a training round)

Quick hint - the round for the GAU-8 looks just like a .308 win - but is as long as my forearm!

 

[Patriot]

Re: .50BMG vs. 20mm

got to bring my .50 cal round home so I can take it's photo next to a GAU-8 round (I have a training round)

Quick hint - the round for the GAU-8 looks just like a .308 win - but is as long as my forearm!

But you're going to spoil my fun....lol. Just kidding with ya. Please post a picture as you may beat be to it. The 30mm looks like a shiny coke bottle.

 

[da.gee]

Re: .50BMG vs. 20mm

My brother brought a (30mm) dummy round back from England when he was posted there in the Air Force in the 80's. We were just playing with it the other day. It is huge. I think it's what the A10 Warthogs use in their gatling gun set up. IIRC from a TV special I saw that gun has 8 rifled barrels about 21 feet long and is accurate out to 20+ miles!! Hello 72 virgins!

EDIT: Thanks Owen for correcting me on the round used! It was definitely bigger than the .30 cal we were shooting that day!

 

[Owen]

Re: .50BMG vs. 20mm

A-10s use 30mm cannon at ~4000rpm. I think they only carry enough ammo for about 20 seconds continuous at that rate, but that's still serious firepower.

No sense of "gunshots", just a continuous roar. Used to hear Vulcans doing live fire pretty frequently, and they sound like bullfrogs off in the distance.

There's just not many things cooler than a "Gatling" gun.

 

[LukeA]

Re: .50BMG vs. 20mm

KE = (1/2)m(v^2), so your power factors are in fact underrating the faster calibers like .50BMG and 20x102.

 

[Patriot]

Re: .50BMG vs. 20mm

My brother brought a 50 cal dummy round back from England when he was posted there in the Air Force in the 80's. We were just playing with it the other day. It is huge. I think it's what the A10 Warthogs use in their gatling gun set up. IIRC from a TV special I saw that gun has 8 rifled barrels about 21 feet long and is accurate out to 20+ miles!!

.50cal M2 is .50x99mm and fires a .088 lbs slug
30mm PGU13/B is 30x173mm and fires a slug over 1lb, and travels much faster.
Also the GAU-8 is has 7 barrels and the max effective range about 4000M.

LukeA
KE = (1/2)m(v^2), so your power factors are in fact underrating the faster calibers like .50BMG and 20x102.

Thanks Luke, I used PF instead of ME to aviod favoring the faster calibers. For example, if we take the .223 and 44mag and compare them by ME vs PF

ME
.223 = 1282 ft/lbs
.44 mag = 1650 ft/lbs

PF
.223 = 170,500
.44 mag = 336,000

As you can see, ME really favors velocity and penetration. If the target is hard enough ME is more accurate, otherwise PF works well enough for informal comparisons and it's easy to calculate quickly.

 

[Illum]

Re: .50BMG vs. 20mm

20mm...

it reminds me of shooting field mice with .45....should it be used against people as an anti-personnel strafe

 

[Bullzeyebill]

Re: .50BMG vs. 20mm

Can you factor in the energy delivered to the target from the exploding 20mm projectile?

Bill

 

[FrogmanM]

Re: .50BMG vs. 20mm

Man that is some serious firepower, scary stuff!

Hello 72 virgins!

:laughing:

-Mayo

 

[alpg88]

Re: .50BMG vs. 20mm

there was a program on tv about p51, one pilot that flew during ww2 said, it was matter of preference of individual pilot how those 8 guns were aimed, some liked wide spray, some liked single(almost) poi.
personaly i'm familar with 12,7mm, (nsv) 14.5mm, and 23mm. can't really comment on .50bmg or 20mm. from numbers i,d say russian 12.7 has a bit more punch than .50bmg, and 23mm has a lot more punch than 20mm. but in reality if a plane gets hit with either it is bad news

also from what my grandfather (ww2 bomber pilot) told me, very few of rounds fired actually hit the plane. flack it the most dangerous, aaa might fire slow but they had huge rounds 75-88mm. one round explosion close enough can easy bring plane down.

 

[KC2IXE]

Re: .50BMG vs. 20mm

Remember that the general ideal of the GBU-8 round is to penetrate the armor (top, which is the thinnest, but) of Sovet Main Battle Tanks (T-62s, and this was pre T-72 in design)

 

[LuxLuthor]

Re: .50BMG vs. 20mm

I don't know what the hell you guys are talking about with all these impressive looking photos, but why not just use a stinger missile?

 

[Patriot]

Re: .50BMG vs. 20mm

there was a program on tv about p51, one pilot that flew during ww2 said, it was matter of preference of individual pilot how those 8 guns were aimed, some liked wide spray, some liked single(almost) poi.
personaly i'm familar with 12,7mm, (nsv) 14.5mm, and 23mm. can't really comment on .50bmg or 20mm. from numbers i,d say russian 12.7 has a bit more punch than .50bmg, and 23mm has a lot more punch than 20mm. but in reality if a plane gets hit with either it is bad news

The P51 had 6 x .50s. Not a big deal but I thought I'd mention it. Most Pilots preferred a 500-1000 yard convergence on their guns and a very few liked them parallel.

Small Arms of the 20th Century 3rd edition shows 2746fps 681 grains. About the same energy as the .50BMG.

The 20mm PGU and 23mm are very close in performance also. The Russian round is longer but it lacks powder capacity because it's narrow. Typically shorter, fatter cartridges burn the power more uniformly and velocity is more consistent from shot to shot.

The 2,3,4 rounds from the right are all GAU-8 rounds, which the A10 and Apache use.

Bullzeyebill
Can you factor in the energy delivered to the target from the exploding 20mm projectile?

haha.....it's funny that you thought of that, but know I cant. Since this was just a fun, generic peak into old vs. new, I didn't even touch on that nor did I think anyone would ask. The explosive difference in the projectiles is massive though. Just a 1 - 3 rounds can turn airframes into smoking, blackened hulks. Between the extra ME of the faster projectiles and their explosive potential, the M61A1/2 system is probably for more deadly than the simplistic way I've portrayed it here. Fun to ponder these weapon systems though isn't it.

Hmmm, I'm trying to find a picture for you ...........

No, luck at the moment. I've got it saved somwhere but it's a helicopter hit by 3 rounds of 30mm airburst ammo. It's nothing but a smoking shell afterward. I'll look for it tomorrow.

LuxLuthor
I don't know what the hell you guys are talking about with all these impressive looking photos, but why not just use a stinger missile?

We were just comparing gun systems. Old standards vs. new standards. The Stinger isn't used on high speed fighter aircraft but some helicopters use a twin rail mount. They're very limited in range and required more thought during the initial aquisition and firing phase compared to other air to air types but they do provide a bare minimum to lightly armed scout aircraft.

 

[LuxLuthor]

Re: .50BMG vs. 20mm

We were just comparing gun systems. Old standards vs. new standards. The Stinger isn't used on high speed fighter aircraft but some helicopters use a twin rail mount. They're very limited in range and required more thought during the initial aquisition and firing phase compared to other air to air types but they do provide a bare minimum to lightly armed scout aircraft.

Oh I get it. This is all just recreational ordinance.

 

[KC2IXE]

Re: .50BMG vs. 20mm

The 2,3,4 rounds from the right are all GAU-8 rounds, which the A10 and Apache use.
...snip...ft.

Ah, I doubt it - 2 and 3 look like GAU-8 rounds, where 4 does not - plus look at the shoulder to base of shell distance (it's called the Datum line) - for a round to chamber and fire, they have to have either the same datum line, or smaller with a jam fit bullet, and then a reduced powder charge (used to create what are called "improved" cartridges - see the term fire forming)

 

[alpg88]

Re: .50BMG vs. 20mm

The 20mm PGU and 23mm are very close in performance also. The Russian round is longer but it lacks powder capacity because it's narrow. Typically shorter, fatter cartridges burn the power more uniformly and velocity is more consistent from shot to shot.


.

???????
23x152 is very close in performance to 20mm pgu???????

 

[Patriot]

Re: .50BMG vs. 20mm

???????
23x152 is very close in performance to 20mm pgu???????

Ah, but you didn't say 23x152 originally, only "23mm" which I naturally took to mean the 23x115. I don't think 23x152 which is actually called the 23x152B has been in operational service with a world power since the early 1960's but I haven't researched it deeply. I imagine it's still being used in some corner of the world until the supply of rounds is depleted. It's the only 23x152 I'm familiar with so slap me if I've missed the mark. :whoopin: :laughing:

KC2IXE
Ah, I doubt it - 2 and 3 look like GAU-8 rounds, where 4 does not - plus look at the shoulder to base of shell distance (it's called the Datum line) - for a round to chamber and fire, they have to have either the same datum line, or smaller with a jam fit bullet, and then a reduced powder charge (used to create what are called "improved" cartridges - see the term fire forming)

ah yes, you're right on the money there. I posted the picture to show the difference between the 20x110 and 23x115 rounds. I just glanced over at the others any saw "30mm" and the overall length. The 4th from the right is the Russian designed, old Warsaw pact round.