It is doubtful that H&R (NEF is long 'gone') has done a comprehensive test fire with full factory loads to X number of rounds to 'duplicate' the effects long term of expected life of the arm.
Engineering will have said it, as built, is supposed to meet/exceed the SAAMI spec, and some testing was most likely done. Will it hold up? Have any products had recalls? Have any H&Rs been dropped from the line for 'issues'? Just how many rounds to they anticipate the owner of one of these to shoot anyway?, not too many, I expect.
My 12ga. OverKill kicks like a mule, and many H&Rs have lasted in that chambering. That is not an SB-2, or high pressure CF cartridge so it doesnt mean anything as a comparison to the 500 except that a heavy recoiling piece can hang together, but a high pressure one may not. I know I could be happy with the 500 performance at well less than full factory loads.
If you want a single shot that will hold together with high intensity chamberings, and has the record to prove it, you might better consider a Ruger No.1