When watching AC-130 gun camera footage, I often wonder how powerful, in the relative sense, those 40mm rounds are in terms of post-impact blast.  Anybody know?  I am guessing...and this is a complete guess, that they fall somewhere in between a 40mm grenade (M-203, for example) and a 60mm mortar?

powerful enough to get your attention!

Enough to fuc3 up any Haji's day?

To me this video is pure win:  CV90-40.

I think you're about right.  Maybe a tad more on the 40mm M203 round side of things than the 60mm.
 

same as a .22lr.. able to go through brickwalls and slay classrooms full of children.
oh, and take out aircraft at 20 miles or so.  

The 40 mm 40 × 311 R L/60 High-Explosive Tracer (HE-T) cartridge (also known as the HEI-T) is the base round for the entire Bofors 40 mm L/60 anti-aircraft gun family and dates back to 1930. Over the years, the basic 40 mm L/60 HE-T round has undergone many changes in filling, fuzing, propellant and materials, but it remains much the same in appearance as the original design. The following description outlines the current Bofors data. For many years, 40 mm L/60 HE-T ammunition was produced by Lindesbergs Industri AB (LIAB), which later became part of Bofors.The 40 mm L/60 HE-T round is still in production and remains available from Bofors on request. Many other manufacturers produce the round on a regular basis, often referring to it as High-Explosive Incendiary (HE-I) or as HE-I-T. Although 40 mm L/60 HE-T rounds were made in huge quantities in the US for many years, including during and following the Second World War (1939-45), they are no longer in US production, other than to special order. The ammunition is used in the USAF's AC-130 gunships under the designation PGU-9C/B. Nammo recently won a US contract to supply ammunition for this purpose.

Description
The 40 mm L/60 HE-T is a fixed round, with a brass cartridge case and a streamlined boat-tailed projectile. The body is made of a special high-fragmentation steel. The cartridge case is crimped rigidly to the projectile by one or two 360º crimping bands. It should be noted that weapons using automatic feed systems or guns with increased rate-of-fire modifications should use double-crimped ammunition. A copper drive band (gilding metal has been used) encircles the projectile just above the cartridge case/projectile junction. Rounds are usually fed into the gun in four-round charger clips.The Bofors 40 mm L/60 HE-T projectile is filled with 92 g of Hexotonal, comprising 42 per cent TNT, 40 per cent RDX, 15 per cent aluminium powder and three per cent wax desensitiser. Many other fillings have been used, for example, the US MV2 700 HE-T SD (self-destruct) contains approximately 63.5 g of tetryl. The base of the projectile contains a tracer element which burns for five seconds after firing.The nose of the projectile may be threaded to accept fuzes with UK, US and Bofors threads. Typical Swedish fuzes for the 40 mm L/60 HE-T include the Type LI 460 PD [Point-Detonating], which functions against 2 mm dural at impact velocities as low as 350 m/s and self-destructs after 12 seconds (on some HE-T projectiles the end of the tracer burn initiates the self-destruct process). The LI 460 PD uses a UK fuze-well thread. The similar LI 462 PD has Bofors threads, and the LI 463

I wouldn't want to get hit by one.  






 
 

Our PGU-9B/B or C/B is the primary combat round.  Its about 3.5 oz of Comp A3 in addition to its incendiary properties.  I couldn't tell you how much is in a M203 round, just Gunship stuff.

Edit: I see much more detailed information beat me!

40mm Bofors - 2lb round with 1/8lb of HE, in general.
40mm Grenade - Not sure on total weight, but only 1.6oz of HE.
60mm - Almost 4lbs depending on round, with various HE fills.
In terms of pure blast, the 60mm is the most powerful, but it doesn't leave the barrel at close to 3,000fps like the 40mm Bofors does.
ETA:



Fusing will also play a large role in how effective such rounds are.  Fuses for penetration will delay and cause the round the explode in the ground instead of on top of it, greatly reducing the effective radius.




 

 

I'm not sure what round the US uses, but the 3P is fucking awesome in airburst mode.

An AC-130 navigator/senso wrote a novelized account of his tours in SEA. (Gunship, Henry Zeybel)
It's really good if you can find it.

The standard 40mm round broke into 250 pieces, none larger then 60grains, at 2500fps. Lethal radius vs personnel was 30-40ft.

The 105mm HE shell broke into 3,000 pieces weighing up to 600grains, at 4,000fps. Lethal radius was up to 200' against personnel, 40' vs trucks.

A friend of mine is a recently retired AC-130H pilot and said that many of the 40mm Bofors cannons were being replaced by the 30mm Bushmaster cannon due to a lack of reliable 40mm ammo.  Most of the ammo he carried on board in Iraq and Afghanistan was 1950's vintage and newer suppliers weren't able to keep pace with demand.  He got out 4 or 5 years ago, so I don't know if that's still the case.

We don't, and probably never will.





The 40mm Bofors is a big gun for the power it packs, and it is only used on the AC-130.  I'm not sure if the old guns can be upgraded to use programmable ammo.





Also, they were looking to replace the 40mm with the same 30mm gun that is going on the Marines Expeditionary Fighting Vehicle to simplify the ammo chain.


 

In case anyone is wondering, the future of 40mm is 40mm Cased Telescoped Ammo(CTA).



http://www.dtic.mil/ndia/2005garm/wednesday/duckworth.pdf




 

I know quite a few AC gunners (even got some kickass spent cartridges from em)  and they have told me of how they have had to ditch multiple rounds in a row because they wouldn't fire.

Pisses off the range controllers as they have to go out and look for em after they dump em.

Pretty close to the truth.  I still fire Navy marked brass from the 40s.

In WWII, the Brits slung two 40mm cannons on underwing mounts onto the Hawker Hurricane and used it in North Africa to kill tanks.

I remember seeing something about that they canceled that idea because the Bushmasters weren't accurate enough.

Prox fused?

Around 6-8 zombies if you can get them to group together.

 

No they didn't.

 

check this out, scroll down to the Mk. II D version  http://en.wikipedia.org/wiki/Hawker_Hurricane_variants#Hurricane_Mk_II

I once met a ex RAF pilot who flew one in N. Africa

Yes, they did.



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Unlikely.  If nothing else, batteries are going to be dead.  I don't think there were proximity fused 40mm available during the '40s, for that matter.

Since the 40mm Bofor was designed for a pretty high velocity gun, the shell has proportionally less HE than the AGL or mortar round.

The times I have seen 40mm frag before, there were a few real relatively large pieces, vice the numerous smaller ones you see with lower velocity HE.

Vickers S gun != Bofors



It's still a 40mm though.

Should be fine for whitetail.

you need more practice at Zombie Gunship, I can get 10 to 12 heads per hit  
The 40MM cannon is friggen cool as hell!!

I believe the Navy's remaining sub tenders still have a couple of 40mm Bofors apiece.  Not sure if any of the Navy's small craft still have them or if any USCG vessels use them, but it's possible.

My apologies, I thought you meant they slung 40mm Bofors guns under the wings, didn't realize you were talking about the vickers guns. Well played Sir.

I wouldn't be surprised if the 40mm guns on the AC-130 are replaced some day with the "new" trendy 57mm caliber.

Actually the first run of early MK. II D's they produced had Bofors 40mm guns they got on lend lease because they didn't have any Vickers cannons available at the time. All other planes manufactured after the first run had Vickers cannons installed.

40 mm Bofors anti aircraft style cannons?

Not Bofors. Those had the 2pdr Rolls Royce gun


http://en.wikipedia.org/wiki/Hawker_Hurricane_variants#Hurricane_Mk_II


http://en.wikipedia.org/wiki/QF_2_pounder_naval_gun#QF_2-pounder_Mark_XIV

Thanks, that's what I read too. A 40mm bofors cannon is far too big to mount to a plane like a hurricane, not to mention the ammunition feed would be a mess. If it existed, I'd love to see it, but this is why I said, a 40mm bofors cannon wasn't mounted to a Hurricane.

looks like I was wrong about the Bofors, my apologies.

It's all good, I was just really confused.

The only combat round in our 57mm inventory is 3P. But I understand that isn't the same as 40mm.

That's demonstrated in this video. Contact fuse (1st round, 'esplodes on impact, throwing up more stuff) versus delayed fuse (2nd round, 'esplodes a fraction of a second after impact, throwing up less stuff). We didn't want to use air burst because it was so close. We probably shouldn't have been that close to those either, but whatever.

No, only prox fuse is for some of our 105s