How do you guys steady a handgun for load development?
Are you sure the problem is how steady you are holding the gun?
I think bds has posted a few times regarding having a known load that you know produces a certain grouping. So let' say you are having problems getting loads to group, take some of the known load ammo and shoot a group. If the grouping is what you expect, then you know the loads you are testing is not grouping well. If suddenly your known load is grouping very bad, then you know something else is going. It could be you or something with the gun.
To me the type of rest does not make that big a difference. For me it is more important to get comfortable. If I feel comfortable, and I can grip the gun that is comfortable to me, and I can focus my aim at a specific spot, then it has to be the loads. Currently I am using a scope for load testing and expect a sub 1" grouping at 15yards for an accurate load. When I was just using the regular gun sights, my expectation was sub 1.5" groupings at 15 yards for an accurate load.
My problem using the regular sights was being able to focus at a specific aiming point since the target was badly out of focus at 15yards.
I don't do it often, but when I do test @ 25yds with iron sights (and no option for laser or scope) I also use a diopter device on my glasses:
http://bulletin.accurateshooter.com/2012/07/diopter-devices-aid-old-eyes/
This allows my eye to better focus on the front and rear sights while still keeping the target in focus.
I was reading up on this today, and actually tried it with just a pin hole in a piece of paper. I could not believe what I was seeing. I was able to focus on my sights and the target without my glasses. Maybe I'll try one of these gadgets one of these days.
At the end of the day I think you need to first identify where the issue is. If it is the loads, then more workup is required. If it is the rest, then work on getting comfortable and trigger control.
I looked at all my grouping data today, and BE-86 in 9mm is not that easy to find an accurate load, well at least for me it is not that easy. I don't shoot the RMR 124gr RN jacketed bullets, so I don't have experience in how easy they are to find a good grouping. In 9mm it has always been easier for me to find a good grouping with different bullets using PowerPistol.