groups: irons vs scope

[darkgael]

I have a problem that I have been unable to solve regarding my DR and barrel to barrel grouping as well as sighting in general.
The rifle is a Rizzini 90L Express rifle, an O/U .30-06.
Pic:

It has a simple, standing rear sight, drift adjustable for windage only. It has a scope mount on it for a Leupold 30 mm scope. I have used it with the scope pretty much all the time. Bottom barrel fires first and is dead on at 100 yards. The upper barrel shoots about 4 inches higher and a couple or three inches left. This grouping is with factory Winchester or Remington ammo 180 grain bullets at 2700 fps. It is the same with my handloads, 180s at 2700 fps.
The other day, I took the scope off and tried using the irons. Well.....the barrels put both bullets within 1.5 inches of each other - with factory and handloads. The problem is that the two shots were 10 inches high.
So...in a sense, the irons shoot better than the scope except for elevation.
I thought that, if I had the bottom barrel sighted in,  the upper barrel would follow. It does not. The second shot using the scope is not nearly as tight as it is with irons.
I, actually, prefer irons - trimmer gun - but at 10 inches above POA?
What to do? suggestions welcome. I  hope that my explanation is clear enough. The simple (not so simple with this gun)  solution would  be to install a taller front. I'd like to avoid that, if possible and not change the original configuration of the gun. Is there any thing to be done sighting the scope that might bring that second shot in?

Pete

[Drilling Man]

  Your rifle must have been "regulated" (the bbls.) without the scope on it, so it goes out of regulation when you put the scope on.
 
  You may find a handload that will get it back into regulation IF you play around with bullet weights and speed, to see if you can find something that will work.
 
  Some DR's will change regulation when a scope is put on and some don't.  It's pretty much the luck of the draw with DR's.
 
  DM

[Black Fly]

I am not an expert on doubles, but have owned and shot several, and done a bunch of stuff wrong in the process. Often doubles dont regulate with a scope when they were regulated without one. I noted you mentioned a 30mm scope. They tend to be heavy. You might try a lighter, smaller scope.  Sometimes that can make a difference. Change in impact with a scope on is a lot about the flex of the barrels. Might be worth a try rather than just give up the scope option, Just a thought.
Bfly

[darkgael]

Checking back after another afternoon at the range.
I have happened upon a solution of sorts. I tried a lighter bullet.
When I acquired the gun, I was told by the previous owner that 180s were the bullets of choice. I could find no contradiction and went with them. Factory 180s (and my handloads) are at 2700fps. Those were 10" high with the iron sights as noted earlier. I tried 165s (Remington PSPs, 54 grains of 4350....my all round favorite load) with the iron sights - i had not tried this before. Too bad, because this load worked very nicely for the way I shoot.  The POI was about 4 inches above the POA as referenced by the top of the front sight. The barrels shot within two inches of each other.
Much better than the 180s.
Pete

[dougk]

...

 I tried 165s (Remington PSPs, 54 grains of 4350....my all round favorite load) with the iron sights - i had not tried this before. Too bad, because this load worked very nicely for the way I shoot.  The POI was about 4 inches above the POA as referenced by the top of the front sight. The barrels shot within two inches of each other.
Much better than the 180s.
Pete

Is this a regulation issue or a harmonics issue?

Also, are double rifles regulated for one barrel to shoot higher for longer shots.  For example the right barrel is set of zero and the right barrel is set for 2 inches high?

[darkgael]

Doug: Thanks for the post. This DR is an O/U, not a SXS.
I don't know the answer to your question. Wish that I did. I don't even know how I would discover which it is.
Here's a pic from Friday, six shots - three each from the upper and lower barrel - 165gr. PSP/54 grains 4350.
Factory iron sight. 100 yards. The hold was on the edge of the seven ring. I was shooting off my elbows. I was happy with this result.

[dougk]

My DR is an O/U also.

The Valmets allow the lower barrel to be adjusted for windage and elevation.  I regulated my 30-06 for top to be zero at 100 yards and the lower barrel to be 2 inches high at 100 yards.

Which hole was the first from the top and the first from the bottom?  I am wondering if your barrels being heated produce a different POI.

Doug

[darkgael]

The barrels definitely heat up quickly; they are quite thin at the muzzle.
The shot pairs: the two at 11 o'clock in the 8/7 rings are the first pair. the two at 10 o'clock and 1215 on the 9 ring are the second pair. The remaining two are the third pair.
The lower hole is the first shot/bottom barrel in every case.
Some of the spread is, of course, me. Not the most precise sights. Not the steadiest position.
Pete

[dougk]

Hey Pete

The first shot from each barrel looks pretty darn good to me...  If your lower first shot was on zero, the second woul be approximately 1.5 to 2 inches high and approximately .5-.75 inches to the right.  With open sight  not to shabby.

When you scope the gun in you might want to use the low barrel as the primary and see where the top barrel goes after the lower barrel is sighted in.  During sight in I found cold bore shots provide the most accurate depiction of hunting situations.

also I like the 1 inch square targets for sighting in and evaluating the regulation of a combo or drilling.

[Drilling Man]

My DR is an O/U also.

The Valmets allow the lower barrel to be adjusted for windage and elevation.  I regulated my 30-06 for top to be zero at 100 yards and the lower barrel to be 2 inches high at 100 yards.

Which hole was the first from the top and the first from the bottom?  I am wondering if your barrels being heated produce a different POI.

Doug

  Your O/U is NOT regulated properly...
 
  First of all, moveing the center bbl band DOES affect the TOP bbl too.
 
  Anyway, a PROPERLY regulated DR (S&S or O/U) will have the individual groups from each bbl. shooting apart, at any range, the SAME distance the bbls. are apart at the muzzle.  It's just that simple.
 
  If the bbls are apart 1" at the muzzle, then the groups should also be 1" apart at any range it's shot at.  That is, the center of the bbls. groups would be 1" apart.
 
  DM

[dougk]

My DR is an O/U also.

The Valmets allow the lower barrel to be adjusted for windage and elevation.  I regulated my 30-06 for top to be zero at 100 yards and the lower barrel to be 2 inches high at 100 yards.

Which hole was the first from the top and the first from the bottom?  I am wondering if your barrels being heated produce a different POI.

Doug

  Your O/U is NOT regulated properly...
 
  First of all, moveing the center bbl band DOES affect the TOP bbl too.
 
  Anyway, a PROPERLY regulated DR (S&S or O/U) will have the individual groups from each bbl. shooting apart, at any range, the SAME distance the bbls. are apart at the muzzle.  It's just that simple.
 
  If the bbls are apart 1" at the muzzle, then the groups should also be 1" apart at any range it's shot at.  That is, the center of the bbls. groups would be 1" apart.
 
  DM

I set up my DR for a quick 100 yard shot with the top barrel and quick 200 yard shot with the bottom barrel.

[Drilling Man]

  It's your DR, and of course you can regulate anyway you want.
 
  Personally, i'd want it right!  The 30-06 and most other cartridges of this size, shoot plenty flat enough to be regulated properly, and then used for a dead on hold, out to 200 on big game animals.  I mean, that's what you would do if it only had one bbl..
 
  BTW, with proper regulation, the bottom bbl. should be fired first.
 
  DM

[dougk]

good point DM. 

I feel I have better trigger control with the back trigger.  Maybe I should make it my primary.

Doug

[pastorp]

There was reciently a interesting discussion over on the double rifle forun on accurate reloading. com . About which barrel was proper for the first shot.  Having been raised on double shotguns, with two triggers, the choise of barrel was always decided by weather the birds were flying away or toward you.
With the double rifle the main concern seamed to be the possibality of doubeling the gun under recoil.    Regardless of your opinion, it was a interesting read..

Regards,