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Subject: 155 mm 45 caliber or 52 caliber Gun
vivekchats    3/9/2007 6:25:53 AM
which gun is better. the 155 mm 45 caliber or 52 caliber. i need to know the advantages and disadvantages of both the weapon systems
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HIPAR       3/9/2007 10:45:05 AM
I would think the required muzzle exit velocity is a deciding factor.

The US Crusader was to employ a 52 Cal cannon.  That length was required to achieve the specified 40 km firing range without exceeding the safe chamber pressures for type accepted 155 mm projectiles.  If I remember correctly, there was also a new charge being introduced;  some projectile types were not use it for safety reasons.

I was there when they uncrated  the cannon after it arrived from Watervliet Arsenal.

---  CHAS
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Sabre       3/9/2007 11:31:13 AM
(While most readers will know this, on the off-chance someone doesn't)
52-calibre refers to the barrel length, so it is slightly more than 1 meter longer than at 45-calibre barrel (155mm x 7 for the difference in length between the two, roughly). All else being equal, this means the propellant has more space and thus more time to combust and for the resulting gas to expand before the projectile leaves the tube, imparting more energy to the projectile, resulting in longer range. (Depending on a variety of factors, you could say an additional 10 to 20km, though I am sure someone will chime in with exact figures for specific projectile/charge combinations.)
The disadvantages?  There aren't many, in my opinion, but apparently they are significant enough that the US can't manage to adopt a 52-calibre weapon... or even a 45-calibre one, for that matter (IIRC, both the M109A6 and M777 are 39 calibres, and currently the NLOS-C will be 30).  A longer tube can be more difficult to manuever and transport, it adds a significant amount of weight to the system (since you also need a more robust carriage /mount, recoil system, etc, to cope with the more powerful recoil).  Depending on your design, and what propellant you fire, the tube may wear out and need to be replaced sooner, if you make a habit of firing the higher charges used to attain that extra range (I've read of experimental designs that needed to be replaced after as few as a thousand rounds, which a tube of artillery in a high-tempo war could fire in less than 48 hours).
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flamingknives       3/9/2007 11:58:13 AM
It's also harder to maintain accuracy with a long barrel. Longer barrels are more susceptible to bending, differential heating, manufacturing flaws etc.

Chucking a shell further doesn't really help if you can't get it suitably close to the target.
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vivekchats    45 v/s 52 caliber   3/9/2007 8:46:06 PM
 Thanks for your views.  But could the increase in range in 52 caliber be so significant as to overcome the disadvantages of weight, a longer barrel and difficulty in moving the gun.  how does the 45 caliber gun score on these counts when compared to a 52 caliber 155 mm gun
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HIPAR    It depends   3/10/2007 10:58:07 AM
I guess that all depends on the missions envisioned for weapon.  Obviously Sec Rumsfeld thought that range was not important compared to transportability. He canceled Crusader just as it was becoming real. 

Using ballistic (unguided) projectiles,  M109 variants can fire to about 24 km. Crusader was firing to about 37 km and was showing promise of reaching its 40 km design goal.  So the lesser calibers have command over 1800 square km while the Crusader would have command over 5000 square km. I always thought that battle space coverage is significant.  I'm thinking Israel would have opted for range during their last 'disagreement'.

Crusader was to utilize a projectile tracking radar to adjust long range fires without the need for forward observation.

---  CHAS

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Berova       3/11/2007 12:51:54 AM
The M777 is air transportable and light enough to allow you to carry ammo. With rocket assisted rounds, it will have  considerable range.

The Crusader had its problems that got it canceled, weight (which goes against strategic mobility and add to the logistics problem) and cost.
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Carl S       3/11/2007 8:22:34 AM
"Using ballistic (unguided) projectiles,  M109 variants can fire to about 24 km. Crusader was firing to about 37 km and was showing promise of reaching its 40 km design goal.  So the lesser calibers have command over 1800 square km while the Crusader would have command over 5000 square km. I always thought that battle space coverage is significant."
As a career artileryman I agree entirely with the need for range.  The last few years spent doing fire planning & coordination at corps/army level drove home repeatedly the need for weapons that can provide fire support across a large battlefield.  

The M777 is air transportable and light enough to allow you to carry ammo. With rocket assisted rounds, it will have  considerable range,

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HIPAR       3/11/2007 12:22:04 PM

The first time I witnessed a radar directed fire mission was during a HELBAT exercise at Ft Sill.  A group of us from Frankford Arsenal (Philadelphia) had designed an automated fire direction center to support the test that was organized by the Human Engineering Laboratory at Aberdeen Proving Grounds.  If I remember correctly, we had the smaller Firefinder (AN/TPQ-36) assigned to the experiment.  It communicated with the FDC through a TACFIRE  radio modem.  After some interface problems (both technical and political) were solved, all went well.

Crusader was to be an autonomous system capable of firing to 40 km.  Crusader spent a large amount of money for an analysis to prove the obvious.  Firing effectively to 40 km without some integrated means to adjust fire was not possible.  Of course the first question asked was 'Why can't we use Firefinder in the friendly fire mode'?  Obviously the answer was 'That's possible but additional Firefinders would need to be procured and a Firefinder unit would need travel with each Crusader battery it supports'.  So they funded development of an on-board projectile tracking radar (much to the consternation of the precision munitions camp). The radar actually continued to receive funding as an emerging technology after Crusader was canceled. 

The radar tracked the projectile until the signal quality became questionable.  The rest of the trajectory was completed by simulation using the GTRAJ modified point mass model.  It was all working very well to 37 km during testing at Yuma with solid tracking to somewhat less than max ordinate.  The testing was conducted off carriage with Form Fit and Function hardware.

Such are the complexities of shooting a long cannon.

So Carl, I'll take issue with your opinion that the radar was only advertising hype.  But, I know you are not the only one who thinks that way.

---  CHAS
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Carl S       3/11/2007 4:16:20 PM
One of the problems with the radars is they produce a signal that can be DF  all the way from Siberia.  Back in the Cold War era setting the transcivers where they would not draw collateral destruction was a not minot tactical consideration for the bn/regiment S3.  The sigintel guys would not tell me the time they needed to locate an AN/TPQ-36. "Thats SECRET sir", but it seemed to less than the time of flight to 25km range.  During Desert Shield we were told the iraqis activated exactly one of their counter battery radars (of the thirty plus sets eventually found in Kuwait.)  it was imeadiatly located & counter fired.

The much weaker signal from the MVsets we strapped to the barrels could also be usefully detected by the sigintel folks.  At least thats what they claimed, & they had the our locations for MV calibration shots as their evidence.   I'm skeptical they could pick up many of those transmissions, but it wasnt my specialty.  

Elsewhere I've been told any future enemy would not have the smarts to use the radar emissions & other US Forces signals.  We are just too superior.  I suspect most of us here would find that attitude more than a bit arrogant and blatantly stupid. 

"It communicated with the FDC through a TACFIRE  radio modem."

You are not refering to TACFIRE as in the 1960s TACFIRE firecontrol system?  I saw it still in use in the mid 1980s, but thought it completely retired in the early 1990s.  Was your test before then, or was the "radio modem" residual equipment?  When I used the IFASS in the mid 1990s there were various parts of the program & hardware bits still present that had interface roles for TACFIRE.  Sort of like vestigal leg bones in a snakes skeleton. 

Outside of my area (in the 1990s) the counter fire radars were being linked directly thru BCS & thence to the Gun Display Units.  Dont have any details on the hardware or connections, other than the standard singars equipment handled the data transfer ok.  I just tracked the missions on my IFASS terminal, drank coffee,  made decisions, and reassured the Col all was well. 
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HIPAR       3/11/2007 7:11:57 PM
For anyone interested about the course of the discussion:

A description of the HELBAT VI  artillery test is in the 1977 Field Artillery Journal at Fort Sill.

 *-" target="_blank">http://sill- cover shows some of the equipment that was tested.  Click on the table of contents Helbat 6 for an article that describes the test.  HELBAT means Human Engineering Laboratories Battalion Artillery Test. Many advanced concepts were tested including fire adjustment by Firefinder.

---  CHAS

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