I just took purchase of a S&W MP10. I want to mount a one inch tube 50mm scope on it. Which Burris XTR rings do I need. I plan to put a free float handguard on it eventually. Can I get by with highs or do I need extra high.
There is a sticky in the Optics section about how to properly measure for the appropriate rings/optic combination that should give you what you need in terms of the MINIMUM height to keep the scope's bell from contacting your forend/handguard. Just remember, if the handguard you plan to upgrade to is a railed unit or otherwise meant to be the same height as the receiver's picatinny rail, what may work now may not work as well down the road, so I'd buy accordingly.
Off hand, and without knowing the particular scope or its measurements that you are dealing with, I'd say you'll most likely want the extra high (1" height) rings to give you the proper clearance of your scope's bell and the proper cheek weld on the scope. YMMV...measure twice...buy once!