The wedge should be tight top to bottom to hold the barrels snug to the forend, but have some slack fore and aft to allow for heat expansion, movement of the barrels.

Guns shoot high or low due to many factors - one is they put sigths on the gun and sell it. No commercial mfgr sights a gun in. Only 'some' custom makers do this.

Having to change the sights on a comercial gun to get it sighted in with the load you are using, is nothing new.

Off centre crowns, ie: more material removed off the bottom than the tops of the muzzles can also throw shots high.

Many American double rifles of the muzzleloading era had the muzzle's filed on the outside to throw shots together when diverging, or filed in the centres to open up those which crossed. There are guns in private collections which show this filing. I am not suggeting you do this- just for your information. It was not done by the mfgr, which was usually Colt, this side of the pond.

The muzzle treatment I do is not "coning". Coning is done with a long tapered reamer, which leave a long gradual taper to the rifling height from the bore diameter to the tops of the lands, extending down as far as 2" into the bores. I have tested coning in several different guns and found coning reduced accuracy in every one of them. In effect, it really was no benefit at all. I have heard some say it improved accuracy. This is possible because: My experiments with coning show these shooters must have had too-sharp a crown to allow using a tight enough ball and patch combination to seal and therefore, once coned, they were able to use a thicker patch or larger ball, and thus accuracy was improved over their original dismal results. However, a properly crowned muzzle is just as easy to load as a coned muzzle- the video's show this, with the added benefit of better accuracy over any coned muzzle.

When I do to the muzzles, allows tight, bore sealing loads to be used. Failure to do this, results in having to use a combination that will not seal the bore, therefore, fouling builds up shot to shot and you have to wipe the bore evdry shot or too damn often, anyway. Due to the buildup of fouling the bore never remains consistant. In ML shooting consistancy is 50% of your accuracy. Shooting a load that fouls makes the bore ever changing and therefore accuracy is degraded due to inconstancy of the fouling in the bore. As you load the next, you clean the prior shot's fouling from the bore, pushing it down on top of the powder. This happens the same every shot and thus, accuracy is assured - if the load is right for that bore, of course.

Some people are resistant to 'fix' their muzzles and thus they put up with having to wipe the bore often due to the fouling buildup. It's your choice - but please, don't complain about poor accuracy or fouling problems or having to wipe the bore due to fouling buildup. The 'fix' is easily accomplished by anyone with a strip of emery cloth and a thumb. Wrapping the emery cloth around a tapered dowel is also a method that works and one I use to get the initial angles right on a larger bore, as in the .69 pictured. I finish the job with 320,m then Crocus cloth for the final polish. The last 2 groups this rifle shot(last summer) were: at 100 meters 1.3" for 5 shot group, and at 200 yards, 6 shot group of 1 1/4" wide X 3 1/2" high - both open sights, off the bench, single bag up front. This should show that minor inconsistancies in my thumb and methods seem to have little impact on the gun's shooting abilities. There are many modern rifles won't do this well - with a scope sight.

One thing to look for, is each barrel of your gun should shoot at most, a 1" to 1 1/2" group for 5 shots at 50 yards off the bags. Large bores easily meet this accuracy & large bores are the easiest to get this accuracy from. they are more forgiving of minor inconsistancies. If the gun does not deliver this accuracy with any load, more load development and/or a muzzle re-crown is in order. The 50th shot should have loaded as easily as the first - no wiping at any time.

The more accurate the gun will shoot off the bags, the more accurate you will be able to shoot it from any position when hunting or target shooting.