The height of each ring is as follows:
Low - 0.775", Medium - 0.950", High - 1.100".
They would hold up the the recoil of the 450 Bushmaster. We would suggest high height for a hunting setup for an AR.
Centerline height from top of rail: Low - 0.775, in Medium - 0.950, in High - 1.100 in
Yes, the Wheeler Engineering Picatinny Rail Scope Rings will have no issues staying mounted to your rifle as long as they are properly installed.
The 34mm Wheeler Engineering Picatinny Rail Scope Rings could work. I also recommend the Spuhr 34mm Separated Rings Rifle Scope Mount for Picatinny Rail located at the links below. The guide at the last link below will also help you determine what height you need for your specific set up.
https://www.opticsplanet.com/spuhr-34mm-separated-rings-riflescope-mount-for-picatinny-rail.html
https://www.opticsplanet.com/spuhr-34mm-riflescope-ring-mount.html
https://www.opticsplanet.com/howto/how-to-how-to-measure-scope-height-scope-ring-height.html
I would recommend using extra high rings for that application. Unfortunately Wheeler Engineering Picatinny Rail Scope Rings only go to a max height of "high" and those may not be enough to clear your objective lens.
Centerline height from top of rail: Low - 0.775 in Medium - 0.950 in High - 1.100 in
No they only come in High, Medium, Low. High for the 1" ring & 30mm are 1.1" base to centerline and High for the 34mm ring is 1.25" base to centerline
Please email us at techsales@opticsplanet.com so we can further answer your question.
Yes, they will work just fine.