I loaded up 4 pcs of T-Rex brass with XMP 5744, 535gr HB .590" cast bullets, and Fed 215 primers.
I loaded 4 different powder charges and here are the results:

40gr - 1169fps
50gr - 1380fps
55gr - 1544fps
60gr - 1562fps

Two of the rounds chambered smooth as silk, one was a little tight, and one (the 55gr charge) was REALLY tight to chamber. The two were tight in the neck area where the .590" bullet was pushing out on the cases brass neck. I was not able to crimp the bullets in place because I don't have a crimp die yet. I think that the 55gr charge attained higher than expected velocities because the neck pressure allowed for better combustion of the powder.

I have ordered a sizeing die which should size them to .5865" which is .0015" over bore size instead of the .005" which they are now. This .005" oversize is the reason for the tight chambering I got on two rounds. Robgunbuilder- you were right - I was wrong, you're smart - I'm stupid, women find you attractive - they throw drinks in my face, etc, etc.

It was fun to shoot it for the first time even though I only had some oversized cast bullets for it. My .585" 650gr Woodleighs should get here today/tommorow so I can load some of them to play with. Also, I should be getting some of the .585" FN bullets with driveing bands soon to play with also. Recoil on my rounds was low, however I was only shooting 535gr bullets at 1500fps in a 14.4lb gun with the scope. Tommorow I'll load some rounds that should take me for a ride this weekend and will be more befitting of a rifle such as this.

BMG- Good show! That 55 gr XMP5574 load I gave you chrono'd out exactly the same as my 500 A2. Works every time. Yup you will do fine with a .0015 oversize bullet. Try Linotype and SPG lube ( by Hand). This is my infamous Baboon load. -rob

Keep us posted on how you go!!!

Won't be long and i'll be posting how I go with my .585.