M-795 projectiles

The Ukrainian military is firing an estimated 6,000 - 8,000 M795 projectiles daily at Russian targets. Two days of expenditures at this rate is roughly equivalent to one month's production of M795 rounds in the United States (at 2022 production levels).   -Wikipedia

Assuming the factory is running six-days-a-week then the US factory has a daily rate between 500 and 600 projectiles. That is in-line with the production rate of a single shift at an automotive assembly plant.

Using the calculations from above, Ukraine (one side of a small brushfire war between two powers both of whose battlefield doctrine relies heavily on artillery) is burning through 13 days worth of US (former-superpower) production every day.

One of the bottlenecks to increasing production is that the forging of the shell of the projectile is a slow process and the dies are subject to wear.

Any effort to increase production will inevitably run into this constraint.

If I ran the universe...

 

I would introduce the M795-NI alternative.

600, deep-draw, one-hundred-pound forgings a day is a lot of forgings.

6000, one-hundred-pound nodular iron castings a day is not since a single foundry will supply all of the crankshafts used by several engine plants (which typically run three-shifts-a-day and six-days-a-week)

Nodular iron is used for vehicle engine crankshafts and MacPherson strut knuckles and in the wheels of train-cars. There is a great deal of automated production available world-wide.

What do you give up by switching to Nodular Iron?

Typical mechanical properties for an as-forged, medium carbon steel might be:

• Ultimate tensile strength of 100,000psi
  
• Yield strength of 60,000psi
• Elongation before failure of 20%
• Mass density of 7.8g/cm^3

Typical mechanical properties of an as-cast, ferritic grade of nodular iron are more modest

• Ultimate tensile strength of 60,000psi (a drop of 40%)
  
• Yield strength of 40,000psi (a drop of about 30%)
  
• Elongation before failure of 18% (a drop of 10%)
  
• Mass density of 7.2g/cm^3 (a drop of about 10%)

There is also a penalty in the uniformity of the mechanical properties, particularly with respect to tail-to-nose as the casting will have different cooling rates due to thickness considerations and the location of the risers in the sand. There is also more variation in mass density than for steel which will cause more variation in point-of-imact.

The smart designer would increase the thickness of the sides of the projectile to produce a projectile of the same mass as the steel version and match the center-of-mass so the ballistics will be identical to the original. That would come at a slight cost in the the amount of high-explosive that can be packed into it.

The good news is that the elongation of the two materials are close. That means that the energy released by the high-explosive will transfer to the kinetic energy of the shrapnel (i.e. the efficiency) will be close.

Given the slow turn-over of the procurement apparatus, it would behoove the Pentagon to start investigating the Dollar General version of the M-795 shell today.