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It has often been asked why should the rifle shell explode prematurely more frequently than the spherical? It may be answered that if the rifle shell is charged with only the same quantity of powder as suffices to fill the spherical of the same calibre, explosions will rarely, if ever, take place. But as the rifle shells hold from three to four times as much powder as the spherical, the greater weight of powder, and that in a long column, must, by its reaction on the firing of the gun, press with much greater force, and by friction, either on the bottom or along the sides of the cavity of the shell, (if left rough as cast,) cause an explosion.

Such being the facts in respect to the explosions of rifle shells, and the means of preventing them, are they the causes of the unequal endurance and unlookedfor bursting of the guns?

I am unable to trace any connexion between the bursting of guns and the time of manufacture. The difficulties of procuring supplies of material and of labor have been unexampled within my experience; but I am not aware of any deterioration in the work, and feel confident that there has been none which can possibly account for the failure of guns, though the supposed necessity for assigning some cause, such as would be applicable to ordinary cannon, has led to the supposition that a gun which fails must have been bad from the beginning. It would be as unjust to expect of me to foresee all the difficulties which may arise in the use of a system of ordnance so new as that of rifle. cannon, as it would be presumptuous on my part to pretend to do it. I cannot think, however, that the merits which mine have exhibited are merely accidental, but believe that, from the uniformity of plan and the results with the extreme sizes, no intermediate class can be wrong in principle. I know of no possible cause, other than the explosion of the shells, which would account for the bursting of my guns near the muzzle. It has been known to happen the very first round fired from the gun after a very few, after some hundreds; and in the two 10-inch guns destroyed in this way-one after twenty-seven, and the other after one thousand and four fires in actual service. In a very few instances it has happened with the 30-pounder guns after quite moderate use, and in one it did not take place up to four thousand six hundred and fifteen fires.

Again, as to those peculiar modes of bursting, by which portions of the castiron are blown off forward of the wrought-iron reinforce, or near the trunnions, after leaving all the rest of the gun still connected together, how can it be supposed that these accidents, occurring after very irregular periods of service, can be the results of any uniform and natural action of the charge? The explosion of so much additional powder as the shells contain, though undoubtedly adding materially to the strain upon the gun, might not seriously damage it; but as the base of the shell will probably be in one piece, with the ring connected, and the sides of the projectile driven laterally against the bore, it is not surprising that partial jamming of these should take place, and try the gun to a dangerous point. I have portions of the front or curved end of a shell burst in the gun, which are so marked as to show these fragments to have been violently forced into the grooves. Although I conceive that the failure of the guns at any part forward of the reinforce is certainly due to accidents occurring with the projectile, I cannot conclude that similar accidents might not cause the bursting of the gun in another part depending on the position of the shell at the time. In one instance, at Morris island, the base of the shell was actually found in the gun after the blowing off the breech.

In other cases the cast-iron may be so injured by previous explosions as, in bursting, to carry the band with it.

In conclusion, I would express my belief that I have correctly assigned the causes of the bursting of my heavy guns. I do not consider that they are less safe than ordinary cannon when subjected to the same regularity of strain.

On account of the very uncertain action of shells prematurely exploded in the bores of rifle guns, we are unable to determine the extent of injury, therefore, and cannot judge of the number of rounds which the guns can subsequently be expected to endure with safety.

At the same time I am satisfied that the means now used do effectually prevent the premature explosion of the shells, and thus remove the greatest cause of danger to the guns, it is due to the subject and to myself that I should advert to the firing of other projectiles than my own in my heavy guns.

I cannot but

think that many shells much inferior to those which the same makers would now supply have been used in my rifle guns, as well as many projectiles of an experimental kind.

The action of powder in the rifle takes place under circumstances very different from those existing with the spherical projectile, and, in my judgment, far too little consideration has been heretofore given to this point as connected with the durability of the guns.

R. P. PARROTT.

NAVY DEPARTMENT, Washington City, June 30, 1865.

SIR: In accordance with the order of the Navy Department of the 12th instant, reconvening the board on rifle ordnance, (adjourned on the 18th January last, to await results of certain experiments suggested by said board, which have since then been conducted by Captain Joseph F. Green, under the particular instructions of the Bureau of Ordnance, hereto appended, and marked 1,) we have the honor to state that we reassembled here on the 27th instant, after having conducted several additional experiments, and inspected the condition. of the guns and projectiles used in the recent trials at Cold Spring, New York,

under the orders of the Bureau of Ordnance.

It appears by the course of the experiments of Captain Green that one thousand (1,000) rounds were fired from each of three 100-pounder Parrott rifle guns of nearly similar weight, density, and specific gravity of metal, and cast nearly about the same period of time, which were selected by the chief of the Bureau of Ordnance, and assumed to fairly represent the guns of that class and calibre now in service. One-half or five hundred rounds from each gun were fired with full charges of ten pounds Hazard rifle powder and the long shell of 100 to 104 pounds weight, and the remaining five hundred rounds with eight pounds of same powder and shells of 80 pounds weight, by your special order to Captain Green.

From one of these guns (No. 242) 1,000 shells "coated" were fired.

From another of these guns (No. 256) 1,000 shells not coated were fired. From another of these guns (No. 239) 1,000 shells brought to weight by sand and sawdust were fired, and with the following results in premature explosions: Coated shells, (long,) 8 exploded within the bore; coated shells, (long,) 3 exploded without the bore; coated shells, (short,) 3 exploded within the bore; coated shells, (short,) 9 exploded without the bore; not coated, (long,) 7 exploded within the bore; not coated, (long.) 1 exploded without the bore; not coated, (short,) 4 exploded within the bore; not coated, (short,) 18 exploded without the bore; and the same number (viz: 1,000) were fired from No. 239, filled with sand and sawdust, for the purpose of testing the relative endurance of this class of gun, independent of premature explosion of shells, and also to test the resistance of the shells themselves to rupture under the effect of the charge of the gun.

Four thousand and eighty (4,080) Parrott shells of 20, 30, 60, 100-pounder

and VIII-inch calibre, have been fired since the 24th June, 1863, in the proof of navy guns at Cold Spring foundry. These shells were either not loaded or had only a blowing charge-in no instance did any one of the shells break. The army during the same time fired a larger number of shells with the same results.

From this it may be fairly inferred that the Parrott shells are never crushed or broken in the gun by the shock of the discharge.

Of all these premature explosions thirty-four (34) occurred with shells prepared with the navy metal-stock time fuze, and ten (10) with the navy time fuze, with the safety plugs removed, in Parrott's metal stocks, and eleven (11) with the Parrott percussion fuze.

The annexed table gives a synopsis of the report of Captain Green:

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From

1 to 200 rounds, Parrott shells, percussion case, from metal stock. 201 to 334 rounds, Parrott shells, percussion case, from New York. 335 to 401 rounds, ordnance shells, metal-stock fuzes.

402 to 476 rounds, Parrott shells, percussion case, from New York. After 476 rounds, navy metal-stock fuzes.

Gun No. 256:

From

1 to 200 rounds, Parrott shells, percussion case, from metal stock. 201 to 333 rounds, Parrott shells, percussion case, from New York. 334 to 400 rounds, ordnance shells, percussion case, from New York. 401 to 475 rounds, Parrott shells, percussion case, from New York. After 475 rounds, navy metal-stock fuzes.

In all the firing there were fired alternately twenty-five rounds from each gun fitted with percussion and time fuzes.

The board added the following experiments (by authority of the bureau) to the foregoing:

Fifty (50) rounds were fired with loaded long shells without fuzes, and securely plugged with wood and metal to exclude from the shells the flame of the discharge, of which number forty-three (43) exploded by concussion in striking the bank, at 1,760 yards distant, one (1) in the gun, six (6) failed to explode on striking the bank, and but one, therefore, exploded prematurely.

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Five of these shells had one to five 6d nai's placed in them to determine the effects of fragments of iron therein; the one having five nails exploded within the gun, and the remainder exploded on striking the bank at 1,760 yards distant. (Appendix A.)

The board also fired ten (10) loaded 100-pounder Parrott shells without fuzes, and with the fuze-holes open; seven of which exploded outside the muzzle, and none inside, and three by concussion on striking the bank, at 1,760 yards distant. (Appendix B.)

There have also been fired by the board several series, consisting, in all, of one hundred and eight 100-pounder shells, placed successively at 5, 10, 15, 20, up to 75 inches, from the full charge of 10 pounds of powder, (as per appendix,) which show that the position of the projectiles so placed lessen the recoil, and does not endanger the gun, while it does materially lessen the range of the projectiles.

It also fired ten 100-pounder Parrott long shells, loaded with the fuze-hole securely plugged, and the base-hole open, each of which (of course) exploded within the gun, near the seat of the charge, and were found in each instance, by "star gauge," to have produced an expansion of the bore equal to .028 of an inch. Recovered fragments of shells were also found to have been deeply indented by the grooves of the bore, into which they had been pressed, (as per appendix D,) thus showing the immense lateral pressure which an exploding shell exerts upon the walls of a gun, and its tendency to rupture it explosively when it occurs in discharging a gun. This tendency to rupture, we conceive, must always be reduced to certainty when the fragments of the broken shell wedge within the bore, as was the case on a recent occasion at Cold Spring with a 100-pounder fired for proof in presence of a member of this board. A fragment of the shell which burst this gun was recovered and inspected by all the members of the board, and its forward rounded end was indented by the rifling of the gun to the depth of .08 of an inch, clearly showing the great force with which it had been turned and jammed into the grooves.

In the foregoing trials all the precautions prescribed by the Bureau of Ordnance for loading rifle guns were carefully practiced, and impressions and measurements of vents and bores made at every twenty-five fires, and always after an explosion within the bore, to ascertain the commencement and progress of defects. And it further appears that all of these trial-guns have withstood the tests of the thousand fires and more to which they have been subjected, under rapid and, when circumstances permitted it, of very rapid firing, frequently averaging two to the minute, and seldom less than one to the minute, which is far in excess of action firing in ships-of-war.

Of the three guns used in these trials all were more or less scored or cracked around the lower part of the bore, while No. 239, that from which the sandloaded shells were fired, was the most deeply so. This gun (by the authority of the Bureau of Ordnance) has been opened, and found to have four cracks, as per appendix annexed (E,) clearly demonstrating that the wrought-iron band materially aided in its endurance.

That this gun should have exhibited deeper cracks than those subjected to the straining effects of premature explosions of shells within the bores in addition to the strain of 1,000 fires, we attribute to a slight variableness in the qualities of the metals composing them, although their fabrication and composition, as exhibited by their recorded history, (appendix F,) and by mechanical tests, show them to be as exactly alike in every respect as it is possible to make them.

After due deliberation upon all the facts elicited by these experiments, and especially on the effect produced upon the three 100-pounder rifle Parrott guns used in this series of firing, with the former trials of this class of gun, where due care has always been observed in loading, we are of the opinion that the Parrott rifle guns of 6 4 inches calibre, and those of lesser calibres, are as reliable as any

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