Mr Bart, thanks for your effort in sending the pics and explanations. My question however was which machine rest. As there are several types, which can have considerable bearing on quality of results. Such one in attached pic made for me by Bo Clerke,which I've long used. Bo is/was a long time high power shooter whom I used to shoot with and against. You may have heard of him. .He made a number of these that are spread around the country. (The rifle in the rest is fitted with strain gauge used for testing pressures) I smiled at mention of the familiar names in your response. Almost all of whom I shot with and against when I was with AMTU at Ft. Benning, and later. They are getting on in years, same as me. I ran into Wig recently, I always though the had the best eyes I knew of but he told me he's since had cataract surgery. When I was at Benning we did a lot rifle and ammo testing such as you described, but it was basic 101 compared to what I learned and did when I went to work at Aberdeen. Which is why I asked who did the testing you described, vis-a-vis amateur or professional. Which is fundamental in evaluating claimed performance vs, valid results, as so often evident in shooting websites. I assume you made the rest in your photos, as it looks rather home-made, but is probably adequate for your use. In another attached pic is a static rest of the type we use at the consulting firm where I work (Part time now.) Speaking of rests, when I was at Aberdeen we used wonderful old rests that had been made by Springfield. I expect there are more of them in storage somewhere and I'd buy one in a hearbeat if I found one. Just as a keepsake.
