doublegunshop.com - home Forums General Discussion German & Austrian Sporting Guns @ doublegunshop.com Regulating a Drilling scope.

Twice I've seen examples where a Drilling scope is wound out to minimum vertical adjustment and yet it is still not where the shooter wants it to be. Where does one make the next adjustment?

For instance, a particular 1971 made Krieghoff Trumpf with a Krieghoff factory 3-claw, 2-piece mount and European mounted scope. Using Sellier & Bellot factory loads, 131g, it shoots 2" high. Using published a Vihtavuori N140 load for rimmed 6,5x57R and various 125-grain to 130-grain bullets, it shoots 3,1/2" to 6" high. There's simply no more adjustment left in the scope to regulate it any better than that. These loads chrony to the published spec, by the way.


The rifle barrel is very accurate, it's not a case of a damaged crown shooting away from point of aim either. It looks fine under magnification. The Drilling itself is in well maintained condition, not much used, (perhaps now we know why!)

The front mount is dovetailed into the rib and high enough it looks like it could be driven out and replaced without needing soldering. I'm guessing that one option would be to replace it with a slightly higher mount. But fitting it to the 2 claws of the old front mount would be a job for a skilled European gunsmith, surely. Not too many of them around here.

The other option that occurs to me would be to take a few thou off the leg of the rear scope mount, where this flat metal around the rear claw sits on the base-mount fitted to the barrel. This would tilt the scope upward somewhat and the barrel downward in a relative sense. Foolhardy or a simple cure? Please let me know.

The mounts are about 4" apart, so any removal of metal would have 900x the effect at 100 yards, so 1 thou removed would equal 900 thou change in POI.

Am I on the right track here or should I just give it a whack with a big hammer? What's the usual procedure?

BTW, the serial number is 71*** and looking at a 'Waffenpass', the small owner's booklet that came with a near-identical Drilling of this era, (serial 74***), Krieghoff used a 6-gram (c. 100 grain) 6,5x57R bullet to regulate the sights, so perhaps a change of bullets, powders and etc., might work. However I'd anticipate a lighter bullet only making matters worse.

Thanks in anticipation.

I solved this issue once by placing a shim under the scope on the rear mount.

Kiwi,
Give the 10gram bullet a try.It is highly likely that Krieghof didn't mount the scope, but maybe used the 6gram bullet with open sights.If the original owner intended to hunt game larger than Reh(Roe), he very likely had the scope mounted to shoot the 10 gram bullet.S&B ammo may be avaliable with this bullet weight.
rtenenbrown,
It seems that shimming under the rear would make it shoot even higher.
Mike

I think you are correct, must have shimmed the front.
it's been about 30 years.
A heavier bullet may be the answer.

Do NOT lower the rear mount by milling or you will move the slot for the claw slider downward absolutely ruining it! If you shim at all, let it be inside the rings, assuming they are not soldered on. Replace the front dovetail at your option. It could be that the scope is the problem--can it be replaced? Often, drillings and other regulated arms must be handloaded till the shot is adjusted to the sights without regard to anyone wanting that extra 100 fps. A dead deer won't know the difference between the two anyway. I would try to get the load to be accurate with the iron sights and then be also doable with the scope. Der Ami may be right about trying heavier bullets...Steve

Thanks guys. Milling the mounts even a few thou did seem to be like fooling with a big, blunt screw driver inside the mechanism of a Swiss watch. But you've given me some much better ideas to check out.

I had a JP Sauer with exactly the same problem and I assumed the previous owner, (a real gun tinkerer), had replaced one of the mounts with a higher one. It was hard to look/sight down the shotgun rib, for instance. But it would let me sight the rifle in to 2" high at 100yds so I could live with it. But this Krieghoff is worse!

I should have mentioned that the Swarovski scope is of the rail type, so any shimming would need to be under the front clamp and how to do this would be a challenge for a skilled gunsmith. I'll see what joy I can get with different bullets and powders worked up,(if possible)to POA.

The scope elevation is marked ab /auf which, if you ever come across it, must I presume mean absteigend (descending) and aufsteigend, (ascending). That had me scratching my head at the range.


Cheers.

Kiwi,
Be very leery of making any changes to the mounts.The "default" position should be the mounts are correct for "something", and the task is to find out what that "something"is.If you can verify that the scope is defective, the maker has a very good reputation and they may repair it(not likely).Replacing a scope in railmounts is not nearly as hard as if it were soldered in.
Mike

Next trip to the range will be with heaviest bullets in calibre to see, as you say, what they might have been thinking when they set this up. However, I'll also try a different powder to see if a different barrel time causes the muzzle flip to select a somewhat different POI for the 125g bullets tried previously. Something must gel sooner or later.

Gale force winds at present so not to best for a sight-in. Good time for reloading though.

What a "European scope" is on your drilling? It may be the elevation adjustment is blocked at the wrong place, if it is f.i. a Hensoldt or Zeiss (west) DIATAL or DIASTA scope or a copy.

Kiwi,
Kuduae, makes a good point.If your trip to the range with heavy bullets, doesn't square you away, check the elevation turret of the scope.Some scopes provided a means to lock the setting( to prevent accidental movement). If there is(are) a (some)small screw(s) on the top or side of the dial, loosen them (don't back them all the way out)and try again.If that works, be sure to retighten everything.
Mike