Re: Navy Arms Smith Carbine barrel question
I heard a story similar to what Joe Plakis and John Holland have remarked of how a batch of the early repro Smith Carbines had got through with the barrels rifled in reverse, so the bores are larger at the muzzle than the breech, except that what I heard came from Bobby Hoyt. He said that when the barrels were heat-treated, the heat-treating was not done in a vacuum such that the hardness of the metal was not uniformly applied, and so the interior portion of the bore was softer than the breech and muzzle. Thus when the barrels were rifled, the cutter cut a little deeper where the metal was soft than where it was hard, and while the bores were not rifled in reverse, because this hardness was inconsistent inside the bore, the depth of the rifling is deeper where the metal was soft. This allows gas to escape around the bullet while it is travelling up the bore, and between the loss of pressure and the bullet being forced to expand then to compress on its path to the muzzle (much like a choked barrel), while this works fine in shotguns, it doesn’t work so well in rifles.
Some of the barrels can be remedied simply by “lapping” the bore: taking a new cast bullet and driving it through the rifled bore using a 1/2" wood dowel to imprint the rifling on it. Then using lapping compound (i.e. jeweler’s rouge paste), coat the bullet in compound and realigning the bullet with the rifling, the idea is that by passing the coated bullet through the bore repeatedly (20 to 30 times or more), this will slowly wear away the higher portion of the “high” rifling and smooth out the bottom of the grooves, making the bore more uniform from the breech to the muzzle. It may require more than one slug to get the bore uniform. For some barrels, this is usually the first step in correcting this problem, and if not successful, then relining the bore is the next step. If you want more information, talk to Bobby Hoyt.
The Smith Carbine I had that Bobby relined in 2003 had the Italian date code of BN (2000), so this problem has re-occurred since the first Pietta carbines arrived in the early 1990s. Before it was relined, the carbine shot all over the place (like a hose pipe); and after it was relined, if I missed anything at 50 yards as small as 2-inches in diameter, it wasn't the carbine's fault.
First Cousin (7 times removed) to Brigadier General Stand Watie (1806-1871), CSA
1st Cherokee Mounted Rifles | Principal Chief of the Cherokee Nation 1862-66
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