EA,
I discovered something on my first safari, practicing shooting from the sticks.
I’m right handed...so get this: My LEFT hand absolutely messes up my shooting! Whenever I support the forearm of the rifle with a hand the way your pix show, I get groups like you are getting. I saw it shooting from the sticks as well. If I supported the rifle from the sticks with my left hand, I flubbed the shots. I cannot explain it but my left hand anticipates the shot and my groups look like almost exactly like yours. BIG 6” spreads.
My answer: get rid of the left hand. From the sticks I either let my left arm hang loose or loop a thumb in my belt and ignore it. I let the rifle “free recoil”.
From the bench I slip my left hand in a triangle to my right shoulder, under the rifle stock. I’m not sure that makes sense. I call it “military style” from the bench. It’s how my dad said the Army taught him back in the day. My alternative from the bench is that I let my left hand rest gently on the shooting bench, basically pointed in the same direction as the rifle.
As the others have said, work on the shooter first. Rifle second. Damned if my left and wasn’t screwing up ALL my shooting.
As an aside, it was DaveDavenport of Leopards Valley Safari who saw the flaw in my shooting from the sticks. It completely changed my shooting, for the better.
PS: I have a dozen rifles. Excepting my .22LR, my Garand with Irons, and my 9.3x74...ALL of my rifles are capable of shooting sub 1” groups at 100 yards. .223, .257 Roberts, 6.5x55, 7x57r, 7 SAUM, 7RM, .308, 300 H&H, 9.3x62, .375 H&H...
No, seriously. No joke. Granted, they won’t do better than 1/2” on my best day...but the hardware themselves...there’s just nothing wrong with them. Any of them will shoot and will shoot confidently enough that I would give any of them to another shooter and know, with absolute confidence, they will deliver if the shooter does.
Damned if my left hand wasn’t screwing up my shooting so badly.
Good luck man!
PPS: yeah, I know. It’s not a conventional shooting style. It’s simply what I have to do to get the accuracy I need for hunting. Much as I’ve tried, I can’t break the left hand twitch. So the answer is, eliminate the problem.