JP vise blocks provide the same support and work for both platforms. I like the MI rod, the JP blocks are better if you have an AR15 and AR10.I disagree on that. Superior to a clam shell for sure, but not a MI Reaction rod. The Midwest Rod with the sail on top locks the upper alignment with the extension lugs. This prevents any possible shear on the extension pin when torquing the barrel nut. Also very handy when mounting & leveling a scope.
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I mean according to JP, they build their rifles in house with these blocks.