Who makes the strongest upper receiver?

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Im confused i thought your barrel was 24 inches and you had a diameter of 1.3" on yours already? You must have 2.

actually the super bull is a .223. waiting on my first grendel barrel. I have several ar's, all of which Ive built (or assembled) with the exception of an oly arms k8 target match 20" and the dpms super bull, which is in my cousins possession, so Ill proly never see it back!