We covered the Boland in a previous string. It's a BPE. Nitro for Black, by definition, is BPE proof. There's no difference whatsoever, and Nitro for Black doesn't represent a separate class of gun in any way. There's nothing that can be safely fired in a Nitro for Black rifle that isn't also appropriate for a BPE. These get a little confusing for some folks because proof is for BPE max pressure using smokeless.

The BPEs remained quite popular for driven game shooting on the continent for quite a while, despite the introduction of newer smokeless loadings like 9.3X74R. The Belgians continued to build them until quite late, when proof was automatically nitro, which leads many to assume that such guns are full nitro proof, which is not the case.