Napoleons (and siege howitzers) as mortars: More data and range tables!

Back in May I wrote about a “suggestion” from Brigadier-General Henry Hunt in regard to firing 12-pdr Light Field Guns – Napoleons – as mortars.  Hunt inquired with Colonel Henry L. Abbot, 1st Connecticut Heavy Artillery and the presumptive commander of the siege artillery to support the Army of the Potomac, about testing Napoleons dug in to fire at high angle.  In that post, I remarked that Abbot “… had not gotten around to trials of the Napoleons as mortars.  Nor would he.”  A few days after the request, Abbot moved to Fort Monroe to join the Army of the James.  Well, I have a correction to make!

Commenter John Wells offereda vague recollection of reading in some period artillery manual or other that the Napoleon could be reversed on its carriage to allow high angle of fire “mortar practice”” At the time, I didn’t recall such, but noted there was mention of siege howitzers employed in that manner.  But John’s comment, coming from someone knowledgeable on Civil War era weapons, had me double checking. Sure enough, a passage from Abbot laid out those experiments with some detail.  John was spot on!

Abbot’s Siege Artillery in the Campaigns against Richmond is like a “practical guide to heavy artillery” and filled with many fine points of technical nature.  In regard to Napoleons mounted for use as mortars, he wrote:

The advantages of vertical fire under certain circumstances are so great, that in May, 1864, a few experiments were made, under my direction, by Captain [Wilbur F.] Osborne, 1st Connecticut artillery, to test the light 12-pounder gun as a mortar.  They indicated that it might be thus used when mortars could not be procured; but the expedient was never necessary in the siege of Richmond.

So, while Abbot could not fill Hunt’s request personally, one of his capable subordinates did.  But while Hunt suggested simply digging in the trail of the cannon to provide the necessary elevation, Osborne worked the weapon in a different manner:

The carriage was dismounted and the gun reversed in its trunnion beds so as to point over the trail. Two parallel skids laid in a direction perpendicular to the parapet and separated by the proper interval, supported the axle at such a height as to allow the breech to be depressed between them sufficiently to give an angle of elevation of 45º to the piece.  The breech rested on a kind of quoin, and it was found necessary to tie the trail down with the prolonge when the gun was fired. With five ounces of powder, giving a range of about 1600 yards, the strain upon the carriage was inappreciable.  Solid shot (weighing 12.12 pounds) were used; and with charges of four ounces and less, the sabot was not detached until striking the ground.  With very small charges the sabot passed below the vent, but the friction primer always ignited the powder.  These experiments were made in grate haste, at the request of General Hunt, chief of artillery, army of the Potomac, only three days before starting for the field, and no very extended trial was practicable.

Abbot provided a table showing the results of these trials:

AbbotVert12Pdr

For comparison, the standard Napoleon load for a solid shot in horizontal fire was 2.5 pounds, giving 1,680 yards at 5º elevation.  So almost the same range, with a lot less powder.  But that’s mortar powder instead of the standard grade cannon powder, mind you.  The ranges cited were for solid shot.  Using shell, I would think the ranges would, as they did for horizontal fire, drop off to around 1,300 yards.  And shells were more practical for vertical fire.

The practical issue with the arrangement used in the tests was the modification of the weapon mounting.  Dismounting a 1,225 pound bronze gun was no trivial matter in the field.  And for the field artillerists, who would need to employ the gun in most cases for direct, horizontal, fire, this would mean two periods of time in which the gun was unavailable for use.  Not to mention the need to bring along wood for rails, as tested by Osborne.

Abbot went on to record similar tests using the 8-inch siege howitzers, which he was particularly fond of (and Hunt was less so):

Similar experiments with an 8-inch howitzer were conducted by Lieutenant Colonel [Joseph A.] Haskin, in charge of the defenses north of the Potomac, in October, 1863. The following are the results obtained by him and communicated in the manner above described.

AbbotVert8inHow

The tests took into account the differences between the older Model 1841 and new Model 1861 versions of the howitzer:

The variation in range between the two models, of which the bores differ only in the form of the chamber, (elliptical and gomer,) will be noticed with surprise. It accords with my own experiments, soon to be given, with the new and old model mortars. The absolute value of the range shows that a considerable economy in powder wold result from using the howitzer instead of the mortar, but in service this advantage would be more than balanced by the greater inconvenience of loading and pointing.  It is, however, a fact worth remembering that vertical fire, in cases of necessity, can be obtained readily and effectively from guns and howitzers.

That last remark is indeed “worth remembering.”  Within fifty years, weapons designers began working with advanced carriages, using stronger steel frames and pneumatic recoil systems, to allow high elevations.  This revolutionized the use of field artillery.  From primarily a direct fire weapon in the Civil War, by World War I the artillery was more often than not employed against targets unseen by the gunner… and at high angles of fire.  In that light, the Federal experiments were steps in an evolutionary course which lead to today’s high powered howitzers:

www.Army.mil

(Citations from Henry L. Abbot, Siege artillery in the campaigns against Richmond: with notes on the 15-inch gun, including an algebraic analysis of the trajectory of a shot in its ricochets upon smooth water, Washington, D.C.: Government Printing Office, 1887, pages 23-25.)

Guns and numbers: Paddy Griffith and some historiography concerning the Reserve Artillery

Paddy Griffith’s Battle Tactics of the Civil War is nearly three decades old now.  Perhaps I’m showing my age by saying the book came out while I was an undergraduate in college.  From a personal perspective, it was a landmark book – the first “dive” I made into the nuts and bolts of Civil War tactics coming at a time when my instruction drove me to consider all the footnotes – and chase those footnotes with deliberation.  Over the years, my well worn copy of the book has yellowed and aged.  Likewise my opinion of the work has aged.  I can’t say I accepted all of Griffith’s ideas at the start.  Nor can I say I have completely rejected all of it now.  But along the way, just as the lines in a pitched battle, the delineation has moved about considerably.

However one point which I can say remained a “salient” throughout, and comes to mind during my recent writings here on the blog, is a passage in which Griffith discusses the ratio of smoothbore Napoleon guns to light rifled guns in the Army of the Potomac.  Leading into the paragraph, Griffith noted some disadvantages of rifled guns – shells tended to drill into the ground before exploding, defective shells, small caliber and thus small bursting charge, and, lastly, the limitations of small bore canister rounds.  Having established at least a need to retain a mix of smoothbores and rifles, Griffith went on to say:

The limitations of rifled artillery were fully understood at the time, and although the Confederates could never get enough for their needs the Union forces complained of an overabundance of this type of weapon.  Early in the war McClellan had decided that the Army of the Potomac needed only one rifle for every two smoothbores, but he never succeeded in bringing the ratio down to less than two rifles to each smoothbore; nor could Hunt force it much lower when he tried to get rid of some of the rifles after the battle of Fredericksburg.  At the start of the Wilderness battle smoothbores were still in a minority and it was only when Grant sent home 122 pieces, in order to disencumber his collapsing road network, that Hunt was able to seize a fleeting opportunity.

There is a paragraph with all sorts of exposed lines and open flanks!  And those flanks are in the footnotes.  Griffith cited two secondary sources for this paragraph – L. Van Loan Naisawald’s Grape and Canister and an unpublished PhD. thesis by Perry Jamieson. While Jamieson’s later works include Attack and Die, Crossing the Deadly Ground, and other works addressing tactics of the era, his thesis is, to my knowledge, still unpublished.   So I’ll not address the one page cited from Jamieson’s thesis as part of my rebuttal here.

However, Naisawald’s book should be familiar to any artillery-minded reader.  Naisawald’s work came out in 1960.  I’ll say it is “dated” and leave the matter there.  That, of course, does not allow me to dismiss it as a source.  Quite the opposite!  The passages cited from Naiswald lead us first to the organization of the Army of the Potomac under McClellan.  Naiswald states,

… the short-range, light 12-pounder smoothbore – the Napoleon – was to be the backbone of his artillery; two-thirds of the field batteries were to be equipped with this weapon, and the remaining one-third with rifled cannon – a new innovation in warfare.

So what was Naiswald’s source?  He does not offer.  I would, however, refer back to Brigadier-General William F. Barry and that initial organization in the summer of 1861.  Barry suggested a ratio of guns somewhat dissimilar to that given by Naiswald, and broke distinctly upon the ratio of guns to howitzers, not smoothbore to rifles.  Only after the Peninsula Campaign did Barry suggest the howitzers and 6-pdr field guns should be replaced completely by Napoleons.

Naiswald went on to say that Napoleon production lagged early in the war while rifled guns rolled out in large numbers.  That, Griffith could have called upon to explain the abundance of rifles.  But the overly generalized statement about gun production falls apart when one considers the raw numbers – guns accepted by the ordnance department, specifically looking at Napoleons, Parrotts, and Ordnance rifles:

Federal Field Gun Production
Federal Field Gun Production

I probably should give you a fancy, colored chart.  But the numbers speak fine enough themselves.  Napoleon production peaked twice – late 1861-to mid-1862; then again in the fall and winter of 1863-4.  Production of the Napoleons, for the Federals that is, ceased entirely after that.  On the other hand, after the initial surge to start the war, rifled gun production remained comparatively steady.  Save one quarter with no deliveries, most quarters included delivery of over 60 guns.  The totals of all weapons is worth considering here – 2591 guns of these three types, where I would estimate the Federal armies (all armies) only needed 1000 to 1300 field guns of all types.  (And that by the way, is one reason we have so many of these guns still around today as memorials!)

Griffith also cites two other passages from Naisawald – one detailing the artillery re-organization made in the Winter Encampment and the other discussing the re-organization made in mid-May.  I’ve linked to my blog posts relating to those two specific changes, to keep things brief. Bottom line here, Naisawald never provides an overall count of Napoleons and rifles.  Nor does he offer any analysis of the ratio.  For good measure, at the time of the reorganization, every corps had an equal number of Napoleons and rifles – 24 of each.  The Artillery Reserve included 36 Napoleons and 24 light rifles (and fourteen “heavy” rifles).  The rifles predominated in the Horse Artillery where 16 Napoleons paired with 44 rifles.  But weight and tactical application was the justification for the disparity in rifles with those horse batteries.  In short – the figures do show a slight majority of light rifles, but only due to the horse artillery.  There was not a “two rifles to each smoothbore” ratio as Griffith stated.

All of this leads up to those 122 guns “sent home” by Hunt.  Did Hunt select rifled guns so as to balance the ratio?  I submit that was not the case.  Hunt chose to reduce every battery by two guns, which in effect retained the ratio.  Aside from that across the board reduction and the 20-pdrs, the batteries that Hunt “sent home” were from the Ninth Corps.  If Hunt was seizing any “fleeting opportunity,” it was to send away some batteries he had suspicions about.

There!  Thus ends a Paddy Griffith rant.  I feel better now.

(Citations from Paddy Griffith, Battle Tactics of the Civil War, New Haven: Yale University Press, 1989, Page 169; L. Van Loan Naisawald, Grape and Canister; The Story of the Field Artillery of the Army of the Potomac, 1861-1865, Oxford University Press, 1960, page 35.)

“Light 12-pounders to be used as mortars”: A Spotsylvania ‘what if?’ from the artillery persepctive

I’m a bit behind on “coverage” of artillery subject on my planned sesquicentennial-themed time line.  So I hope you readers will indulge as I back-track here (and a few more times over the next few weeks), chronologically speaking.  The letter below properly fit into a post for the first week of May when I referred to the Army of the Potomac marching out of the Winter Encampment.  Among the last letters Brigadier-General Henry Hunt sent from his headquarters near Brandy Station was this message to Colonel Henry Abbot, 1st Connecticut Heavy Artillery and designated commander of the siege trains:

Artillery Headquarters, Army of the Potomac,
May 4, 1864.
Colonel Abbot:

My Dear Colonel: I have received your note of the 1st instant, and am glad to see things are progressing so favorably. I see you have as yet no Coehorns shipped, and that reminds me to ask you how many Coehorn mortars can be got. We will probably need all we can get. I have eight with me, and it would be well for the Ordnance Department to collect all they can. We move to-morrow; so you will soon hear from us in some shape, and will know about how soon the siege train will be required. Address as usual.
Truly, yours,
Henry J. Hunt,
Brigadier-General.

Aside from the “My Dear Colonel,” this message doesn’t raise many eyebrows.  Though it is important to note that even on May 4, before a single shot was fired in the Overland Campaign, Hunt recognized the need for Coehorn mortars.  And he wanted a lot more than eight.  But we knew that already.

More interesting to us artillery-types is the postscript:

P. S.–Would it not be well for you to set apart a few men, with a good officer with some experimental practice with light 12-pounders to be used as mortars, i.e., try the ranges with different weights of powder, and see how the carriage will stand it, if necessary, to throw very heavy showers of shell in curved fire? I think that by digging a hole, and so lowering the trail–diminishing the charge–we will, at a pinch, be able to turn our light 12-pounders to very good account. Provision should be made, if the experiments prove satisfactory, to send on short notice a supply of 12-pounder shell. Can you send me, with your next letter to headquarters Army of the Potomac, a table of ranges for heavy rifled guns–30-pounder Parrotts and 4½ inch? I have none, and would like to have them about me; also a copy of heavy artillery.
Yours, truly,
H.

Let me work this from the end back.  Hunt’s staff, having planned around the use of field pieces for the last year, now needed a refresher on heavy and siege weapons.  Hence the need for range tables for those heavy guns.

But the really interesting section is the request for trials using Napoleons as mortars.  For those less acquainted with Civil War artillery, the standard carriages used during the war allowed a dozen degrees of elevation, give or take depending on the gun and carriage.  For true vertical fires, the weapon must have at minimum 45º elevation.  The only way to achieve such elevation for a Civil War field gun on a standard carriage was, as Hunt suggested, to put the trail in a hole.  And since with the trail in such arrangement, the gun could not recoil, the firing charge had to be reduced lest the force destroy the carriage.

You might ask, what advantage might be gained by firing at such high angles?  A tactical advantage.  With more elaborate field fortifications appearing on the battlefield, the horizontal fires of conventional field guns, and even to an extent howitzers, was at a disadvantage.  Both sides built up heavy front works – higher parapets made of heaped earth and logs.  The penetrating power of direct fire artillery – even the rifles – was not sufficient to break such barriers without a prolonged bombardment.  But vertical fire,  such as from a mortar, could place a shell beyond those works, and do great damage to the defenders.

So how did those trials go?  Three days later Abbot sent this update:

Fort Richardson, VA., May 7, 1864.
Brig. Gen. H. J. Hunt,
Chief of Artillery, Army of the Potomac:

General: Yours of 4th instant is received. There are only five Coehorns now at arsenal, but the rest are expected very soon, and fifty have been ordered with all possible speed. I have ordered experiments with the light 12-pounder gun as a mortar to-day, and will report results as soon as obtained. The Ordnance Department has an abundant supply of ammunition for them on hand. I send by this mail a copy of heavy artillery, which contains an addition to the old range table prepared by General Barry, giving the best rifle ranges known to me; also a similar table prepared by Captain Treadwell, Ordnance Department. I inclose a table of experiments on the new-model 10-inch mortar, to show the difference between the Gomer and elliptical chamber; also a copy of a report of some experiments with spherical case from a 10-inch mortar, which are so successful that I have ordered a large supply of 12-pounder spherical case balls for our train. I also think of taking two 12-pounder Whitworths along. They make elegant sharpshooting to dismount guns. They are very light, and may be of service for such special uses. The following is the present condition of my train afloat: 4½-inch–18 guns. 20 carriages, 20 implements, 20 platforms, 6,520 rounds; 30-pounders–10 guns, 20 carriages, 10 implements, 20 platforms, 5,025 rounds; 10-inch mortars–10 guns, 10 carriages, 10 implements, 10 platforms, 2,000 projectiles; 8-inch mortars–20 guns, 9 carriages, 20 implements, 2,600 projectiles; 8-inch siege howitzers–10 guns, 4 carriages; Coehorns–3,796 projectiles; 100-pounders–6 guns, 6 carriages, 1,400 projectiles; 1,250 barrels powder, 1 battery wagon, 1 forge, 4 sling carts.

Very respectfully, your obedient servant,
Henry L. Abbot,  Colonel First Connecticut Artillery.

Only five more Coehorns?  I should mention Brigadier-General Albion P. Howe’s report on the Washington Defenses from May 17 tallied over twenty Coehorns in the forts.  As indicated in Abbot’s letter, the desired range tables and a lot more information went forward to Hunt.  (Two other interesting topics here – the 12-pdr Whitworths and the 10-inch mortar case shot – I will save for later posts.  The latter becomes important at Petersburg, particularly in the Battle of the Crater.)

But he had not gotten around to trials of the Napoleons as mortars.  Nor would he.  Two days later Abbot received orders to move his force to the Bermuda Hundred and join Major-General Benjamin Butler’s force.  At that point, Abbot’s attention was to operations at the front and not ordnance experiments. UPDATE:  Abbot wasn’t able to test, but his subordinates were.  See this post.

However, consider this “what if?”  Going into the Overland Campaign, the Army of the Potomac had over 100 Napoleon guns.  What if the requested experiments had gone on earlier in the winter, with a proper and refined employment method, to include range tables, been derived?

Now… what if the assault on the Bloody Angle has been initiated by 25 or 50 or even 100 Napoleons firing shells at high angles into the Confederate works, instead of just eight Coehorns?  Granted, as the employment of the Coehors on May 12, 1864 demonstrated, poor accuracy of vertical fires in the black powder era argued against its use in close proximity to friendly forces.  But a preparatory bombardment to open the way for an infantry assault was possible. Similar bombardments supported assaults on entrenchments over fifty years later during World War I.  And for good measure, unlike 1917’s trenches, the Confederates at Spotsylvania had no prepared overhead cover.

(Citations from OR, Series I, Volume 36, Part II, Serial 68, pages 373, 484-5.)