Rib Picture And POI


Dear Technoid,

I am a little confused, I just purchased a 12 guage Browing Gold sporting clays automatic. The gun comes with three shims, that go imbetween the reciver, and but stock. The shim that came with the gun has the same thickness at the top and bottom. The other two are opposites, one is thinner at the top, and one is thicker at the bottom. I patterned the gun with holding the center bead just below the front bead, and the gun shootes low. and very low when using the shim with thin top, and thick bottom. I have used both shims and no better results. How can I make this gun shoot higher without using the center bead?

Jerry

Dear Jerry,

It’s only been recently that Browning has followed Beretta and Benelli to use a shim adjustable stock. That’s my excuse for not having looked over Browning’s arrangement yet. When I tested the Browning Gold sporter a couple of years ago, the shimmed stock was not offered.

The idea being shimming a stock to make it fit better is good as far as it goes. Your point of impact (the center of the pattern) will move in the same direction as you move the stock. Example: if you move the stock up, the center of the pattern will move up. A move of the stock to the left (cast on) will move the pattern left… and so on. It’s exactly like the rear sight on a rifle or pistol. Of course, what is really happening when you adjust a stock is the “aiming” eye is what is being moved and the front bead is what is remaining steady.

I’m a bit unclear what you are doing with your bead alignment and stock movement. If your bead (front and middle) alignment remains the same even after a stock shift, then your point of impact (POI) will remain the same. Even if you raise your stock with the shim (the one that is thin at the top and thick at the bottom will raise the stock the most), if you scrunch your face into the stock a bit harder to retain the previous sight picture of the middle bead just below the front bead, then your eye really hasn’t moved in relation to the front bead, so the pattern will not change.

The pattern may or may not change dynamically when you shoot the gun the way you do at targets, not by aiming it at the paper. It all depends on how much cheek pressure you use. By adjusting your cheek pressure, you can adjust how you see the beads. Of course, this amount of flexibility really isn’t good. You should always shoot with the same amount of cheek pressure if you can. This will assure the same sight picture for each shot.

In theory, if you change shims to move the stock comb up, your sight picture will change and your gun will shoot higher. If this isn’t happening, it’s quite possible that the stock is so low for you to begin with that you use very faint cheek pressure to see the beads and a small adjustment in stock height doesn’t make any difference.

Do a couple of tests. With an unloaded gun mount it a few times with your eyes closed. Then open the aiming eye. What do you see? Is that the rib and sight picture you want? Fool with the shims until you see what you want when you raise the stock with your eyes shut with normal cheek pressure.

Now go and check the gun for POI with that sight picture. Aim it like a rifle, but use the sight picture that you get when you raise the gun with your eyes shut. How does it shoot? If you are getting stacked figure 8 beads and the gun still shoots low, then you are going to have to see more rib to raise the point of impact to what you want. Usually, my guns seem to shoot flat (50/50) when I have a figure 8 bead setup and am seeing a bit of rib. You’d think that they would shoot high when you see a bit of rib, but all my guns are flat rib guns. None have ribs raised at the rear. My guns shoot flat with a very slightly squashed figure 8 and that’s what I consider ideal for how I shoot.

So, you have the bead picture you want and you have the “highest” shim in the stock that the gun comes with. The pattern is still low. Now what? You have to raise the stock more, that’s what. Go the local drug store and get some Dr. Scholl’s “Mole Skin”. It’s in the foot care section. Cut three or four thin strips and layer then on the top of the comb where your face goes. Don’t add tape over the insides of the stock as that will alter cast.

Now your sight picture may show a separation between the middle and the front bead when you cheek the gun with normal pressure. Go check POI. It ought to have moved up. Add and subtract Dr. Scholl’s Mole Skin until you have the POI where you want it. Ignore the middle and front bead relationship. Just shoot off the front bead. Sooner or later you’ll get the POI where you want it. It may not be with the middle/front bead relation you want, but that’s not as important as having the POI where you want it.

Now go shoot the gun with that nasty moleskin on it for a month. This is because you may find yourself adding and subtracting moleskin as you fine tune the POI. When you get it to shoot the way you want, even if it is showing more rib than you would like, that’s how the gun shoots for you. To make your adjustment permanent, you can either tinker with stacking shims (I don’t know if this will work on the Browning) or take it to a gunsmith and have him do it right.

Bottom line: many people think that a certain rib picture automagically dictates a certain POI. That’s not always the case. Unless your rib is adjustable as it is on a few trap guns, if the POI you want and the rib picture you insist on don’t coincide, it’s new gun time. Either that or pay to have the rib replaced.

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)

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