68-pounder Lancaster gun
68-pounder Lancaster guns were a British rifled muzzle-loading cannon of the 1850s that fired a 68-pound shell. They were fitted in pairs to the Arrow-class gunvessel. The cannon was designed with an oval bore and had a range of about . The gun had a tendency to burst. References

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Naval guns of the United Kingdom
Victorian-era weapons of the United Kingdom
Military equipment introduced in the 1850s