I JUST ADDED 5/8" TO MY BERETTA 303 TRAPGUN RIB AND THEN RAISED THE COMB 5/8" AS WELL. ON PAPER AND THEN SHOOTING STRAIGHTAWAYS-- THAT GUN SHOOTS EXACTLY THE SAME!!! NOW I WILL AGREE- YOU'D NEED A SMALL STEPLADDER GET UP ON THAT 11/2" RAISE ( ASSUMING THAT IS MEASURED FROM THE TOP OF THE FLAT RIB SURFACE)
Answer me this, if the gun shoots 90/10 at 13 yards then what is the pattern percentages at 40 (you cannot just multiply by 3 to get the pattern at 39 yards since the shot is still rising at 39 yards minus the 3 to 4 inches that gravity effects the shot)?
So Neil and all you other guys , if I would like to add say 1 inch to the rib, that way I would be able too level my eyes. Then what do I do with the comb so that the gun will still shoot a 60/40 pattern.
Just make the comb-change a tiny bit more than the rib one.
The change would be so small you can't "make" it that way in advance what with the many things that are going to change when you add that much to the comb. Better to make it higher than needed, then sand and file it down so you see a bit more front bead over the mid, or a bit more rib, or whatever it is you see.
If you go to the Keen Sight website and check in the "traditional bead barrel" section. There is a picture credited to Dennis. That is my gun, if you want to see what a 1.5" addition to a rib looks like. Mine was necessary because I am apparently related somehow to a giraffe and was having trouble getting down to my rib and still seeing out.
If you mount the gun in the same place on your shoulder (and this is key), there will no POI change. The only effect of adding the same rise to comb and rib is your head will be more erect. The gun will shoot in the exact same spot - you haven't changed the geometry - only your head position.
Joe, I ask you. Say the rib Rio was contemplating was a foot tall. And he wanted to add a foot to the comb. Would it shoot in the same place - or a foot lower? After all, all he's changed is his head position.
Although you are technically correct, for practical purposes, the vast majority will not notice a 1" shift in POI if we raise the sighting plane by 1".
Essentially, there is no discernible change in POI.
I cannot hold a gun steady enough to see a 1" offset at 30+ yards - where I hit the birds. None of us B shooters can hold well enough, or consistently enough, to notice a 1" difference.
AAA shooters are not the norm. Maybe they can tell if a gun is shooting 1" lower. But, from my limited experience in patterning, they will need to shoot more than a handful of shells - as there are shell to shell variations that could be at least that significant.
No argument from me on that, Don. It won't make any difference. But that's not what was asked
Rio: "Will the gun still shoot 60/40 ????"
And to that the answer remains no.
Remember, people are saying _exactly_ the same (or worse yet that angles will take care of it:
MRDucks: "The gun will shoot in the exact same spot - you haven't changed the geometry - only your head position."
And all I'm doing is pointing out that what they say isn't true. It's not different enough to measure, but it's _not _exactly_ the same.
I'm sort of assuming the Rio is estimating when he quotes 60/40 which really makes the difference a non-issue, nor do I think that adding an inch to a stock and making it fit again is any small task, but it's what he asked and I stand by my answer.
The reason I make my point is that at close-up POI testing, that sort of thing can be detected and will make a difference in the final calculation if you make one, though I don't anymore.
Sure I could have told RIO that he'll never know and that would be true too, but the geometric question is not one you can argue about; the gun will shoot lower.