I have a Krieghoff Plus drilling, with a clawmounted scope. Without the scope, the rifle- and shotgun barrels will fall together. But with the scope mounted the shotgun barrels will shoot a little low..
Not much. Actually I think it won`t make much of a difference in a practical hunting situation. But I really can`t get it out of my mind..
Any suggestions about what to do..? What`s the reason for this problem..?
(posted also on Gunsmithing)

The reason most likely is barrel harmonics which are different when a scope is mounted.
Usually the shotgun barrels are used without a scope so the gun�s reagulation seems to be correct. If you want it differently, try different bullet weights. I would presume that a lighter bullet *might* shoot a little lower. This is what happens in my combinantion shotgun/rifle.

I also thought of barrel harmonics. But since the barrels shot well together without the scope, it seems that the gun itself haven`t been affected by scope-mounting.
Or did you mean that the barrel harmonics will change everytime I take the scope on and off..?
When a gunsmith is mounting a claw mount, will the barrels usually be affected, or will a good gunsmith avoid this?
Thanks!

Do you mean that that slugs in the shotgun barrels shoot low? If so then change the load or just aim off. These guns are so complicated anyway that you must expect things like that.

Sometimes other reticules in the scope can be used for aiming such as the top of a plex. Changing the power on a variable moves the point of impact also on such reticules that are not single plane.

No, not slugs.. "Normal shots"..
The centre of the pattern seem be 4" low. I like a shotgun barrel to shot a little high. Maybee centre 4" high or something. Something like a 60/40 pattern, 60% of the pellets above aiming point, and 40% below..
I agree with you. Combination guns and doubles seem to be pretty complicated..

Are you hunting birds with a scope? I happen to have a drilling and also have 1X and 4X scopes. When I am bird hunting the scopes stay in the car. At this point in the season the black bears are open too and I would use irons for them with the rifle barrel in my Sauer 16X16X8X57JR.

I have shot skeet and crazy quail with the 1X on but for woods walking the gun is a really neat shotgun at 7lbs and it's 23.5" barrels without the scope. It's really ideal in that application. I only put the scope on for deer hunting or group shooting.

On drillings in general. If you really want to get "something" a drilling is about the deadliest gun in my experiance.

Normally I hunt birds without the scope attached, so the scope is primarely used for shooting with the rifle barrel. An exception is driven hunts, where roe deer might be shot with shotgun and scope.
The drilling is a great gun! And I use it as often as I can. Especially when combining birds and other small game with big game..

Anders, I tried to contribute my $.02 over on the Gunsmithing forum.
- mike

Anders

The added weight of the scope above the barrels can retard the barrels rising at the normal rate. This would throw the shot and even the rifle bullet low. Since the scope is set for the rifle you will not notice this on it but the shotgun will tell the tale.

What kind of scope do you have? Is it a heavy scope? You might try to use a light scope or sight the scope for the shot. Since the velocity (time in the barrel) between the rifle and the shot is much different the rifle will be less effected.

The scope I have mounted is a Schmidt & Bender 1,5-6x42. It`s a pretty heavy scope, compared to normal "drilling-scopes" (1-4x..).
I guess the added weight will influence the gun.
I have thought of sighting in the scope for the shotgun, and then try different riflebullets/-loadings, and see if they fall better together. But I think it will be very difficult. 10 cm difference on 25 meters is 40 cm on 100..(?)

I have seen a little difference when using different shots, so I`ll keep on shooting..
I might just try to calm down, with the fact that this guns really are sensible..
Thanks to everyone for very informative answers!

Anders, I have to agree with DUK and Sauenjaeger. Mounting a scope (or anything else) on the barrels will change their harmonic frequency, and thus you will have variation in POI.

Not much you can do about it. It's one of those things that you have to accept when shooting a drilling or double rifle.