Found this. You probably found the same thing-
"My 500 JRH is a Freedom Arms conversion by Jack Huntington.
Here's a target I shot at 52 yds rested from the top of the toneau on pickup using a 4x Leupold. Only shot 3 ea to reduce target clutter and minimize recoil induced fatigue.
Close up of the target:
I've chronoed the following loads at 5 long paces from the muzzle and 60 Deg F
440gr WLNGC 10.0gr HP38 ==== 900 fps
440gr WLNGC 15.0gr HS6 ==== 1,050 fps
440gr WLNGC 14.0gr Longshot == 1,100 fps
440gr WLNGC 26.0gr IMR4227 == 1,200 fps
Have use both Fed 210 and CCI 350 primers. On the loads that I've chronoed, there is no diff in velocity.
Have used 440gr WFNGC from Cast Performance, Leadheads, and Rim Rock (they appear to be identical).
Have used bullets from 350gr Horn to 460gr Lee (advertised as 440gr) with the 15.0gr of HS6.
Never chronoed the 31.0gr H110/400gr WFNGC shown on target above, but recoil was noticeable.
My gun is sighted in for the 440gr/15.0 HS6/1,050 fps at 50 yds. If given the opportunity, will try it on an elk when the general season opens in Oct. Getting to old to enjoy the T Rex loads any more.
FWIW,
Paul "
***WARNING***READ THIS FIRST*** The following is NOT pressure tested load data. It should not be considered safe or usable, as there are no known SAAMI specifications for the 500JRH cartridge at this time. The 500JRH is a wildcat cartridge, proceed at your own risk. Now, on with the show.
I worked up some loads for my BFR 500 JRH using a Lee C501-440-RF w/GC, 2400 and WLP. So far I've only used H110 (27 - 29 grains) and Trail Boss (7 - 8 grains). I found a reference using a 440 over 24 grains of 2400 in a FA83 500WE.
http://www.handgunsmag.com/2010/09/2...xpress_080207/
I assembled 19, 20, 21, 22, 23 and 24 grain loads with WLP primers, Starline 500S&W brass trimmed to 1.397, 1.800 OAL and a heavy roll crimp. I made 5 rounds of each. I plan to put 4 of each over the chronograph. The fifth will be measured for OAL change and shot over the chrono with a 500mag HandiRifle. If the weather is above freezing, I'll do it this weekend and report back. It's likely someone has been down this road before, but I haven't been able to find and references.
Charge..Avg f/s...Change in OAL
19gr..... 956 .......+.006
20gr......1001......+.004
21gr......1046......+.006
22gr......1106......+.006
23gr......1164......+.005
24gr......1199......+.014
I used a 5.5" barrel and used a WLP primmer. My results with 24 grains showed 1199 f/s
View attachment 551225
This is my observation.
Be careful using WE data in the JRH, I've found the JRH follows the 475Linebaugh load data closer than it does the 500WE.
Jack Sent some data with my brass I 'll see if I can Dig it up, and yes he told me to use 475 Linebaugh Data
Free Online Library: The .500 JRH.(TAFFIN TESTS: THE SIXGUNNER HIMSELF: GUNS, GEAR AND MORE) by "American Handgunner"; Hobbies and crafts Travel, recreation and leisure Computer action games
www.thefreelibrary.com
You might want to also consider 350 & 400 grain bullets for the JRH.
Once you pass the 1,250fps mark with the 440 grain pill, it starts talking back and upon crossing the 1,400fps barrier your trigger finger just might take a good pounding every now & then.
Your finger just might take a hit every now & then at 1,200fps +. Shooting gloves above the 1,100fps barrier just might save a little skin and a pint of blood over time.
The Micarta grips are fine if you stay under 1,100fps – better yet under 1,000fps. The rubber bumpers IMO are needed at 1,100fps plus.
Here’s a start:
440 grain – 6” barrel – WLP primer - Oehler 33 Chronograph
H110 – 30.0 grains – 1,356fps
N110 – 24.0 grains – 1,237fps
N120 – 25.2 grains – 920fps
N120 – 27.8 grains – 1,075fps
N120 – 32.0 GRAINS – 1,235fps
IMR4227 – 23.0 grains – 947fps
IMR4227 – 30.0 grains – 1,304fps
IMR4227 – 32.0 grains – 1,379fps
HS-6 – 14.0 grains – 976fps
HS-6 – 15.0 grains – 1,033fps
Lil’Gun – 31.0 grains – 1,428fps
500 grain Hornady XTP
Lil’Gun – 24.5 grains – 1,178fps
And, the guy that invented it-
www.jrhadvancedgunsmithing.com
Shoot an e-mail off to that website, see what you can get for info