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C3 105mm EFC Reference

Matt_Ubbing

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Does anyone know where I could find a specific reference for EFC's? I.e. Chg1=.25 and Chg7=1 . I've been hearing conflicting information and no one seems to be able to give me a clear answer. I swear I saw it in some publication somewhere....can't find it again though.
 

TSM A

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Have you looked in the Gun history books? they should have the formulas for EFC's in them so you can do the conversion when entering daily record of rounds fired. Just a thought.
 

Petard

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The EFC values are at the front of the tabular firing table for that weapon.
For the specfic type you're asking about, the TFT ref # is C-71-332-000/DF-001 (pg x and xi)

The EFC's for the C132 HEER round are only an approximate until more data is collected. The restriction on firing the C132 with the C3 was recently lifted, but allowed firing that specific round at charge 1 only.
Given the recent problems with the C3, that approval will most likely be rescinded
 

Matt_Ubbing

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I didn't have the Gun History books in front of me. I have to e-mail the Record Rounds Fired to the various RSS WO's around LFWA, or at least to the "owners" of the howitzers fired. TFT's though....aha! Got it! Good ol' Army.ca, when I can't find the answer myself, I ask army.ca haha. Thanks a bunch!
 

GnyHwy

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The EFC's for the C132 HEER round are only an approximate until more data is collected. The restriction on firing the C132 with the C3 was recently lifted, but allowed firing that specific round at charge 1 only.

Kinda defeats the purpose don't you think.  Just sayin.
 

Petard

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I'm not tracking. Even the EFC values for the M777, when it came into service, were mostly theoretical estimates until more empirical data was collected; why should it be any different for a gun like the C3 that hasn't fired that many rounds of a specific ammo type.

What ends up happening usually, with howitzers, is the wear limits are achieved before the fatigue limits. To account for this the EFC count is used primarily as a cyclic measure to cue the weapons tech to take wear measurements (typically about every 500 EFC's)

In anycase the gun was permitted to fire the C132 round, cautiously, with wear to be measured every 50 EFC's. One of the benefits of that would be more accurate data.
 

GnyHwy

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I was just talking about firing an extended range projectile at charge 1.
 

Old Sweat

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GnyHwy said:
I was just talking about firing an extended range projectile at charge 1.

That's what I thought you meant. Mind you, it is not the strangest restriction I have come across. For a short period, when we were having a bunch of prematures circa 1963, we were restricted to Charge 7 only, with a maximum QE of 400 mils. As I recall, we also had to do straight line deployments and could only traverse 200 miles left and right of the Centre of Arc. Eventually we were firing CVT set for ground burst in lieu of PD fuzes until new boosters could be procured and fitted to the existing stock of M51 fuzes, which became overnight, ta da, M557s.
 

Petard

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Back when we thought the 105 was an operationally deployable gun, the C132 round was acquired as the operational round for that gun.
But the round was not intended for general training use in the LG1, even less so for the C3.

Even at charge 1, the C132 is more powerful than the M1 ammo and M67 propellant at charge 7, and has a range ~14km
Problem is the full chg (there are only 2 BTW) is very erosive, chg 1 not so much (~1.4 EFC IIRC).

A study done about a decade ago, determined the LG1 will reach its wear limit (but not fatigue limit) in ~500 rounds or so firing C132 full charge. The C3 was not tested that much with this type of ammo, since it would cost a barrel, and ordinarily there wasn't any training need to be firing ammo that "hot" anyway. This is why there had been a restriction on the C3 firing this HEER (High Explosive Extended Range) rd

The reason for lifting the restriction on the C3 to fire C132 is to mitigate some of the consequences of the ongoing M1 shortage.

Technically, a C3 that has had its cradle inspected and been put back into service could fire HEER ammo today.
Its a good thing someones asked this question about EFC's though, because in this case its reminded some people (at least those that visit this site!) of how very important the units stay on top of the EFC count.
 

Matt_Ubbing

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In case anyone has the same brain fart I did:
for C3 Wear coefficients:

Type Of ammuntion                  Charge        Wear Coefficient
HE, M1
Illum M314A3, C103
Smoke WP M60 Series                Chg 1-6    0.25
                                                  Chg 7        1.00
Proof                                                            2.00
M200                                                            1.4
                                                                    1.8


Ref: C-71-332-000/DF-001    C3 TFT's page x, xi



and be careful about using the formulas in the gun history books. There must have been some changes to the wear coefficients at some point because I've seen in numerous GHB's that Chg 6 coefficient was 0.36
 
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