200 French 4-pounders where bought by US from France in 1777? (see Supplying Washington's Army, an excellent document, on the web.) 175 were the short 4-pdr. shown and the rest were the long 4-pdr., about 1.5 times heavier and a couple of feet longer than short one. Knox thought them all much too heavy for their caliber so either had them bored out, or is thought to have melted many down to provide metal for casting lighter guns or howitzers.
These two are undoubtedly of that lot. The first one in the slideshow has been fired so much the bore measures close to 4" now.