On the XM-25 thread, somebody (my apologies but I forget who) suggested a weapon using an updated PIAT system.

This made me wonder if you could reduce the weight of such a weapon by using a long recoil path with a sort of API system. So, you pull the spigot back and fit the bomb. When you pull the trigger, the spigot and bomb travel forward under spring pressure and at some, ballistically expeditious point, a firing pin is triggered which ignites the propelling charge while the spigot is still travelling forwards. The recoil must therefore first stop the spigot's forward travel before it begins to recoil.

I'm not suggesting that the PIAT system is a system worth looking at - it's advantages of low firing signature and no back blast don't seem to outweigh the disadvantages of a heavy weapon with decidedly odd firing characteristics and a, possibly, less than reliable action - but I just have a fondness for odd solutions and actions (which is why I really like the Madsen LMG).

The spigot lunging forward on release was apparently hell on the accuracy so I expect that no is the short answer. A seawater countermass seems the current solution to firing in rooms, which might be less ideal but certainly is a much simpler solution. 

jxexqx said:

This made me wonder if you could reduce the weight of such a weapon by using a long recoil path with a sort of API system.

I may be misunderstanding the operation of the PIAT, but isn't the spigot already moving forward at the point of ignition?

Mustrakrakis said:

I may be misunderstanding the operation of the PIAT, but isn't the spigot already moving forward at the point of ignition?

Yes. The moving spigot strikes the rear of the bomb to initiate firing so the first thing that happens is the 200 pound spring throws the steel bar forward into the base tube of the bomb and then the bomb fires with the spigot being thrown back into the launcher and hopefully hooking on the sear and the bomb sails off in the other direction. 

Wouldn't slight variances in projectile angle / precession at the point of main motor ignition cause accuracy issues, seriously limiting effective range?

Then again, RPG doesn't ignite it's main motor till downrange either.

Plus the PIAT weighed over 30 pounds. Countermass systems for RR / RPG / LAW are heavier than nothing but still lighter than that.

Refleks said:

Wouldn't slight variances in projectile angle / precession at the point of main motor ignition cause accuracy issues, seriously limiting effective range? Then again, RPG doesn't ignite it's main motor till downrange either.

Yup the bomb is just laying in the tray at the front and the tube is overbore for obvious reasons so accuracy was fairly uninspiring.

RPG doesn't use a boost motor on it's HE round so it potentially more accurate. 

https://en.wikipedia.org/wiki/RPG-7

Realistically though a sealed round in a container with an attached sight module is the way to go since it allows for enclosed space countermasses. Everything since the RPG-29 has worked that way and it would be an obvious addition to the LAAW.

That sounds an awful lot like Russell s Robinson's 70mm caseless AGL idea.

I dig it

Thanks.  I thought it was something like that.

In the context of the original question, it sounds as if something similar (if not technically the same) as API is already happening with the PIAT.

Mustrakrakis said:

In the context of the original question, it sounds as if something similar (if not technically the same) as API is already happening with the PIAT.

The thing to take away is a 200 pound spring that is cocked on firing by the long suffering gunner offering sufficient resistance when the main charge detonates.  Also keep in mind the bomb wandered off at the speed of a thrown tennis ball to about 200 metres. Getting the velocity up to something usable and the range out to 600+ metres would require something other than a spring. The design is a half-assed soft recoil system that does not I suspect scale that well. The device mentioned above that sat on the users shoulder is I suspect the logical  evolution of this principle. 

edit: opps, it was in the other thread.

This beastie  https://www.youtube.com/watch?v=HyAl9qK3Rlg&ab_channel=meankitty42

Funnily enough, what you call the velocity of a thrown tennisball, is exactly the same velocity of a 40x46mm grenade-launcher.

I am pretty sure the PIAT could throw a grenade much further than 200ms, but with very little accuracy.

I was the one mentioning the PIAT in the other thread, and I think it could be feasible to scale a launcher to 40x53mm, or even a little bit bigger.



40x46mm projectiles weigh 239g and are launched at 76m/s = 18,2 kgm/s

40x53mm projectiles weigh 255g and are launched at 237m/s = 60,4 kgm/s

PIAT projectiles weigh 1,1kg and are launched at 76m/s = 83,6kgm/s

HIWS projectiles weigh 1,5kg and are launched at 100m/s = 150kgm/s

20x42mm (Neopup) weigh 0,11kg and are launched at 310m/s = 34,1 kgm/s

Energa rifle-grenades weigh 0,765kg and are launched at 75m/s = 57,4 kgm/s

It should in my opinion be possible to even make a 40x53mm launcher even without the PIAT-principle. But a launcher employing the PIAT-principle could probably be substantially lighter, while still being possible to be fired by most people from both prone and standing positions.

The much flatter trajectory, shorter time of flight, and possibility to use programmed air-burst should make the gun much more effective than 40x46mm, and as the 40x53mm is already an established NATO-standard, it is already in the system, which both simplifies logistics, and also lowers the cost and risk of development of a handheld launcher.

Firing the PIAT (Finally) - YouTube