The Gallery Practice rifle uses an auxiliary extractor and the chamber is offset to the 6 O'clock position. The Stevens -Pope conversion does not have the auxiliary extractor and  so the chamber is in the 12 O'clock location.

Stevens-Pope barrels are not exclusive to Model 1898 rifles. Mine is on an 1896 rifle.

You can see the chamber differences in the photograph. Gallery rifle on the left, S-P on 1896 in the center and a Norwegian .22 carbine on the right.

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