Tony Williams

[Bronk]

Quick question for you.
Say you were to ridgedy mount a ww2 era .50 cal so it had no movement at all. Now with said weapon continusly fire a belt or so of ammo through it.
Would the 50 shake itself apart or not?

Bronk

[Pooface]

well, if you made it so no movement was possible, then no, because the gun cant shake itself to pieces


im sure tony will know:aok

[Oldman731]

Originally posted by Bronk
Quick question for you.
Say you were to ridgedy mount a ww2 era .50 cal so it had no movement at all. Now with said weapon continusly fire a belt or so of ammo through it.
Would the 50 shake itself apart or not?

I imagine that would actually extend the life of the gun.  Same idea as coastal artillery, on a smaller scale.

- oldman

[Tony Williams]

I think it would increase the stresses on the gun, but more significantly it would put far more stress on the mounting. In an aircraft wing, it would be like placing a jackhammer against the structure.

Tony Williams: Military gun and ammunition website and discussion forum

[101ABN]

No, it wont shake the gun apart... i have had .50 mounted to my vehicle in the past and they are steady... fired tons of rounds out of them.. since all parts inside the gun move during fire.. the reciever remains steady... also, the barrel will move with every shot too... its all about the head space and timing of the weapon.  i can imagine as time went by during the war, barrels were replaced after long active missions and then after time the whole gun system would be replaced since you cant just replace the bolt and bolt carrier. Ive spent 12 of the last 14 years of my army life with a M2  .50 cal... love it!!!

[Ghosth]

It would burn the barrel out to where its no longer accurate.
But I doubt it would shake the gun apart.

Takes a pretty decent mount though, as your talking pretty substantial recoil several times a second for a long time.

[HoHun]

Hi everyone,

This won't happen in practice because it's impossible to built a perfectly rigid mounting, but in an ideal world, a rigidly mounted gun shooting from a locked barrel would have to shake itself apart.

Laws of thermodynamics: Energy added to the gun frame in the form of vibrations would add up to the point of self-destruction because it can't be transferred out via the mounting. (There is also transmission by air, but I don't think noise could get out the energy quickly enough :-)

An API blow back cannon like the MG FF or the MK108 might be different because if fires from a moving barrel so that some of the kinetic energy of the barrel is transferred to the gun gases.

However, the perfectly rigid mounting is more of a theoretical case, a normal rigid mounting (like screwing the gun down to a concrete slab) probably absorbs enough energy to avoid this effect.

There might be weapons specifically requiring a somewhat flexible mounting and these might break in the real-world from an overly rigid mounting (or their reliability might deteriorate), but I'd not expect that to happen to the 12.7 mm Browning M2 to any noticable degree.

Regards,

Henning (HoHun)

[Oldman731]

Originally posted by HoHun
An API blow back cannon like the MG FF or the MK108 might be different because if fires from a moving barrel so that some of the kinetic energy of the barrel is transferred to the gun gases.

M2 is recoil operated.

Moreover, the question assumed a perfectly solid mounting.  I don't see any difference, in that case, between the perfect mounting and a gun with a receiver that weighed several tonns.

- oldman

[HoHun]

Hi Oldman,

>M2 is recoil operated.

What I meant is that (except for the bolt) there are no parts moving forward at the instant the cartridge ignites. A forward moving part, as in an API blowback weapon, could "expel" energy from the gun. In the M2, that's not possible.

>Moreover, the question assumed a perfectly solid mounting.  I don't see any difference, in that case, between the perfect mounting and a gun with a receiver that weighed several tonns.

A slab of concrete is elastical in itself. If you'd put a seismograph on it, you'd see all hell broke loose on the paper strip. That would be the vibration transferring energy on the block. An ideally rigid receiver would be not transfer any vibrations (which are density waves) since all its atoms are locked in place.

(Taking this further, maybe the real block of concrete out in space with no contact to other matter would shake itself apart into floating sand and pebbles if the gun is fired for long enough :-)

Regards,

Henning (HoHun)

[Bronk]

Thanx for the input so far. So could we expect that a too rigid heavy mg mount would be detrimental to the weapon in the long run?



Bronk

[Widewing]

Originally posted by 101ABN
No, it wont shake the gun apart... i have had .50 mounted to my vehicle in the past and they are steady... fired tons of rounds out of them.. since all parts inside the gun move during fire.. the reciever remains steady... also, the barrel will move with every shot too... its all about the head space and timing of the weapon.  i can imagine as time went by during the war, barrels were replaced after long active missions and then after time the whole gun system would be replaced since you cant just replace the bolt and bolt carrier. Ive spent 12 of the last 14 years of my army life with a M2  .50 cal... love it!!!

Several years ago I was at a Navy facility (NSWC Crane) to do some testing on M2HBs. We had attached a device that records firing and stores the data for future download. It monitored weapon timing, being able to record shot times to within a millisecond.

We set up our hardware on the test range and a Master Chief Gunner's Mate and a couple of junior POs bring out an newly refurbished M2HB, with an immaculate parkerized finish. It looked new, but I asked the Master Chief to double-check the head spacing and timing as I wanted a tight gun to avoid skewing the data. He dutifully opened the receiver and using his head space gauge, verified it was ok. They then loaded a belt of ammo, cycled the charging handle the required two cycles (half-load, full-load) and we began with the goal being to shoot short bursts of 3 or 4 rounds.

However, after just two rounds, there was a misfeed. Recycling the charging handle seemed to fix it and another attempt was made. Again, there was a feed jam after two rounds.

They open the receiver and fiddle around a bit. Reload, two pulls on the handle and shoot... Another jam. After some swearing by the Petty Officers, I stood up and looked at the weapon myself. I'm quite familiar with the M2HB, although I hadn't handled or fired one in years. It took about two seconds to discover what the problem was. I strolled over to the Master Chief and took him aside.

"Chief, the rear stop is missing."

"It's what? It's missing??"

"Yeah", I said, "there's no rear stop installed."  

He walks over, looks and goes bonkers. After reaming the GM2 who signed off the weapon, he has them go get another from the armory.

When the new gun arrives, the Chief inspects it personally.... He discovers an issue when checking it with the timing gauge. So, we waited while they adjusted the timing. Finally we were able to do the test.

The lesson was easy to see... Never depend upon an armorer to give you a functional weapon. Inspect it yourself, and shoot it to verify function and accuracy.

My regards,

Widewing

[HoHun]

Hi Bronk,

>Thanx for the input so far. So could we expect that a too rigid heavy mg mount would be detrimental to the weapon in the long run?

To the weapon or to the mount :-) Remember that a rigid mount tends to be brittle and might crack due to the stresses.

Or it could be the gun frame that takes the worst abuse, and I figure gun life is normally limited by all other parts than the main frame, so you wouldn't notice anything in normal operations.

So it's hard to say what would happen - I figure there would be no way around "fatigue" tests, actually firing the weapon from the intended mount.

Fatigue tests were introduced in an aviation context, by the way - when the famous Comet jetliner had a number of unexplained crashes, De Havilland set up the first airframe fatigue tests and found that the fuselage broke apart at the square cabin windows' corners due to metal fatigue.

Regards,

Henning (HoHun)

[Tony Williams]

As far as affecting the gun is concerned, I think that a rigid mount might cause more vibration which could lead to parts being shaken loose earlier than they would have done.

It does of course depend on the power of the weapon: rifle-calibre MGs are typically fixed to rigid mounts (although some of the latest remote-control, video-sighted, powered mountings have hydraulic absorption to achieve the highest accuracy). HMGs usually have some buffering. So do cannon, with the exception of the API blowbacks like the MG-FF and MK 108, whose mechanism spreads the recoil kick over a much longer period - they have 'internal buffering', if you like.

Other cannon varied a lot. The Hispano needed a 25mm recoil absorption movement between shots, with the MG 151 it was 18mm. With the big airborne anti-tank guns it was of course far more.

However, I repeat that IMO the most drastic effect of a rigid mounting wouldn't be to the gun, but to the aircraft it was fitted to. If nothing else, the vibration would be severe.

Tony Williams: Military gun and ammunition website and discussion forum

[TimRas]

Originally posted by HoHun

Fatigue tests were introduced in an aviation context, by the way - when the famous Comet jetliner had a number of unexplained crashes.
Henning (HoHun)

The first systematic study and tests of metal fatigue was started much earlier, by Mr. August Wöhler, a German engineer. He was the first to study fatigue and propose an empirical approach. Between 1852 and 1870, Wöhler studied the progressive failure of railway axles. He constructed the test rig, which subjected 2 railway axles simultaneously to a rotating bending test. Wöhler plotted the nominal stress versus the number of cycles to failure, which has become known as the SN diagram. Each curve is still referred to as a Wöhler line.

[101ABN]

Originally posted by Widewing
Several years ago I was at a Navy facility (NSWC Crane) to do some testing on M2HBs. We had attached a device that records firing and stores the data for future download. It monitored weapon timing, being able to record shot times to within a millisecond.

We set up our hardware on the test range and a Master Chief Gunner's Mate and a couple of junior POs bring out an newly refurbished M2HB, with an immaculate parkerized finish. It looked new, but I asked the Master Chief to double-check the head spacing and timing as I wanted a tight gun to avoid skewing the data. He dutifully opened the receiver and using his head space gauge, verified it was ok. They then loaded a belt of ammo, cycled the charging handle the required two cycles (half-load, full-load) and we began with the goal being to shoot short bursts of 3 or 4 rounds.

However, after just two rounds, there was a misfeed. Recycling the charging handle seemed to fix it and another attempt was made. Again, there was a feed jam after two rounds.

They open the receiver and fiddle around a bit. Reload, two pulls on the handle and shoot... Another jam. After some swearing by the Petty Officers, I stood up and looked at the weapon myself. I'm quite familiar with the M2HB, although I hadn't handled or fired one in years. It took about two seconds to discover what the problem was. I strolled over to the Master Chief and took him aside.

"Chief, the rear stop is missing."

"It's what? It's missing??"

"Yeah", I said, "there's no rear stop installed."  

He walks over, looks and goes bonkers. After reaming the GM2 who signed off the weapon, he has them go get another from the armory.

When the new gun arrives, the Chief inspects it personally.... He discovers an issue when checking it with the timing gauge. So, we waited while they adjusted the timing. Finally we were able to do the test.

The lesson was easy to see... Never depend upon an armorer to give you a functional weapon. Inspect it yourself, and shoot it to verify function and accuracy.

My regards,

Widewing

ha ha ha ha... guess you would call that case "operator head space and timing" ha ha ha:rofl