Mixed Batteries and Mixed Ammunition

Captain Charles Green’s Battery, the Louisiana Guard Artillery, of Lieutenant Colonel Hilary P. Jones’ Battalion went into action on the first day at Gettysburg with four guns.  Two of Green’s guns were captured 3-inch Ordnance Rifles.  The other two were 2.9-inch or 10-pdr Parrotts (of either Confederate or Federal type).

Green’s battery first deployed, along with two other batteries in the battalion, on high ground east of Rock Creek in support of General Jubal Early’s Division, then falling upon the Federal right flank north of Gettysburg.  Not long after deploying, one of Green’s guns ceased firing.  The reason was not for enemy action, but rather due to ammunition.  Rounds for the 3-inch guns lodged in the bore of a 10-pdr Parrott.

Green’s report indicates one gun went out of action, temporarily, due to ammunition miss-matches.  Jones’ report alludes to three guns temporarily going out of service due to shots wedged in the bores.    Lieutenant J. M. Gregory, Ordnance Officer for the Second (Confederate) Corps Artillery, cites reports from Lieutenant William Fontaine of Jones’ Battalion referencing two Parrott 10-pdrs out of action on the first day.  Fontaine elaborated further on other ammunition supply issues involving 2.9- and 3-inch ammunition, to include fuse compatibility.  [See OR, Series I, Volume 27, Part II, Serial 44, pages 458-459, 495-496, 497-498.]

Regardless of the number of Parrott rifles affected by the ammunition confusion, the simple fact remains incompatible weapons in close proximity raised the risk of mistake – be that on the training field or in combat.  However, as happened on the first day at Gettysburg, given time to respond a gun crew might overcome the mistake and extract the lodged projectile. Just meant the gunners had to work a little harder.

The “stuck in the bore” problem is just one of the issues raised by mixed batteries.  In the pre-war days, mixed batteries were the norm and not the exception.  But such mixed batteries paired up 6-pdr guns with 12-pdr howitzers, or 12-pdr (heavy) guns with 24- or 32-pdr howitzers.  Considering the bore sizes involved – 3.67 for 6-pdr, 4.62 for 12-pdr, 5.82 for 24-pdr, and 6.41 for 32-pdr – lodging the wrong ammunition in the bore was practically impossible.  Still mixed batteries presented tactical concerns, or shall we say limitations.

Keep in mind the number of rounds carried in the ammunition chests for the different calibers:

  • 6-pdr field gun – 50 rounds per chest.
  • 12-pdr Napoleon – 32 rounds per chest.
  • 12-pdr field howitzer – 39 rounds per chest.
  • 24-pdr field howitzer – 23 rounds per chest.
  • 32-pdr field howitzer – 15 rounds per chest.
  • 3-inch rifle or 10-pdr Parrott – 50 rounds per chest.
  • 20-pdr Parrott (or James Rifle?) – 25 rounds per chest.

And the chests contained a specific mix of fixed ammunition.  Here’s the breakdown for the most commonly used smoothbore types:

  • 6-pdr field gun – 25 solid shot, 20 spherical case, and 5 canister.
  • 12-pdr Napoleon – 12 solid shot, 12 spherical case, 4 shells, and 4 canister.
  • 12-pdr field howitzer – 15 shells, 20 spherical case, and 4 canister.

The crews manning these cannon offered relatively uniform rates of fire, although the poor fellow fetching the 32-pdr shell might be a step or two behind his counterpart hauling a 3-inch Schenkl shell.

Lots of variables, particularly the tactical situation, governed the rate of fire, but let us presume a one round per minute for argument’s sake in a “battery on battery” scenario.  The battery commander with a mixed 6-pdr gun/12-pdr howtizer battery could keep his two 6-pdr gun sections on line firing for 45 minutes, firing all the shot and case, before calling for another ammunition chest from the caisson.  On the other hand, the howitzer section might last only 35 minutes, leaving only canister in the chest. Thus the battery commander had a variable, in addition to all the others he weighed, to keep track of. Perhaps even prioritizing resupply of the howitzers if the duel continued past thirty minutes.

The commander of a uniform 12-pdr Napoleon battery could expect at most 28 minutes of fire from one chest.   But he didn’t have to worry about prioritizing resupply to a specific section.

In the pre-war mentality, or even reaching further I might as well say in the “Napoleonic” picture of how a battle is fought, this difference in “on the line” endurance was actually part of the plan.  Guns, after all, were supposed to set up and slug it out with direct fire.  Howitzers were there to support the gun line (or infantry) not duel with enemy artillery.  Experiences, in some cases dating back to the Mexican War, and practical thought changed that mentality among the Army’s top artillerists.  On the battlefield, one rarely has the luxury of selecting the choice weapon system for a tactical situation.  Recall that General William F. Barry began advocating for uniform batteries in the summer of 1861.

Since I’ve brought up Barry’s organization of the artillery in those early months of the war, consider also his recommendation for ammunition supply per gun – 400 rounds.  This is yet another tactical limitation imposed by mixed batteries.  For a battery to possess 400 rounds per 6-pdr field gun or 3-inch rifle, it needed eight ammunition chests per gun.  For a 12-pdr field howitzer that number increased to 10 (rounding down at that).  So figure one of each chest on the limbers and three more chests on the caisson.  For that hypothetical 6-pdr gun/12-pdr howitzer battery, there were four more 6-pdr ammunition chests per gun with the trains, and six more 12-pdr ammunition chests per howitzer.  And, by the way, a 12-pdr howitzer chest weighed 480 pounds, compared to the 6-pdrs 375.  Howitzer ammunition was more space on the wagons and more weight on the axles – requiring more horsepower to pull.  Most inefficiently, one-third of the battery required nearly half the horsepower dedicated to transporting ammunition.

Now in fairness, the 12-pdr Napoleon needed twelve-and-a -half chests per gun – I’ll round up to thirteen.  Aside from those on the limber and caisson, to maintain the desired 400 rounds each gun had nine chests on the trains, weighing 485 pounds each.  Although requiring more horseflesh, the Napoleon battery offered at least equal distribution across the horseflesh resources (in addition the well known advantage from the muzzle end of things).  The battery commander didn’t have a fifty-fifty chance of getting the wrong ammunition chest, as they were all packed the same.

So what is the big deal?  Well, often technical and logistic factors are the governors of the tactical options a commander has to consider.  The tenth of an inch bore size difference that limited the options of Confederate artillerists on July 1, 1863 is easily documented.  However, the logistical factor at play – the inefficient allocation of horsepower per ammunition chest – due to mixed batteries is less easily recognized from battlefield accounts.