Now I know it's a thumpper vs a real thumpper. But would I be giving up much going with the rigby over the 500.
My way of thinking is the 450 will shoot a 600gr if need be and with 500gr's should have less recoil.
The only thing that made the a square interesting is it looks to mirror a 500 NE in a bolt gun. I have no interest in a 500 jeff or a 505 gibbs.
Another reason for the 450 is I will also have a 416 rigby soon.

Any of the above 3 (500 A2, 500 jeffreys, or the 505 gibbs) can be loaded to duplicate 500 nitro ballistics with very conservative pressure levels. in my 505, 126 gr H4831 gives 2100 fps with 600 gr woodleighs, viz actually significantly better than the 500 nitro
the real dvantage of the 500 a2 is the cheap brass(neck up 460 wby) and large selection of .510 bullets, including milsurp 50 bmg for plinking.
The 450 rigby is enough gun for any conceivable application, IMO. Recoil on the 'half inchers' is significantly greater, and most riflemen who dont practise shooting big bores regularly cannot shoot even the 450 rigby accurately. the reason for the greater recoil with the 500's is the larger case capacity (especially the Gibbs at 173 gr water), thereby requiring larger quntities of powder to attain the same velocity. I dont know about the A2, since the 450 rigby is essentially a 416 rigby necked up to 458, while the 500 A2 is a belted 416 rigby necked up to 510. using the same quantity of powder should provide similar recoil characteristics with the same weight bullet in identical rifles; pressures will be a little lower in the 500A2, at the cost of an insignificant decrease in velocity

If its for Alaska ,..,The 450 is generally more useful ...but there are now plenty of lighter weight bullets for the 500 now.. ...If its for African heavy and dangerous game the 50 caliber is a good bit bigger for the same recoil ....And it has a pretty good rep .,.,Because I had one and would like another I would go with the 500 ..., Plus there isn,t alot of difference between the 416 and the 458 ., Where as a 416 Rigby and a 500 A-2 would make a great combo ..IMHO

.........My 500 A-Sq. had a 21" barrel and 116 gr of IMR 4320 gave me 2350 fps avg velocity with the A-Square triad and the Barnes Origanals and belly button solids .. That was the recomended load befor Art got his pressure testing equipment .,.,After pressure testing they backed the max off 1 grain to 115 gr of IMR 4320 ..108 gr of the same powder gave like 2125 fps ..I never really felt I was undergunned with the starting load ...

You may want to look at jeffeosso's 500AR. It will easily duplicate the 500NE, and do it from a standard lenght action.

Keith

I'm going with the 450 Rigby now and will build a 500 A square later, like in 2008.

God once you catch the bug it's like a drug lol.