Not a question; here is what happened to me this week. My 9.3 Chapuis X4, shoots into one inch easily, at 50 yards, without even trying and without adjusting the barrels. And with a random hand load. Luck? Maybe. Now, I decided to put a different scope on it, one that weighs 5 ounces less than the zeiss with which it shoots the little left and right groups of any number of shots.
It immediately was turned into a 3 inch left and right horizontal dispersion rifle!!!
I couldn't believe it so I fired more lefts and rights; each barrel into one inch, but separated by 3 inches. Go back to the Zeiss, 5 ounces heavier; BAM; all shots into less than one inch every time.
Just goes to show you how they can react. Can the barrels be adjusted to bring them back together? Probably. I ain't going to mess with it.

[QUOTE]Originally posted by dpcd:
Not a question; here is what happened to me this week. My 9.3 Chapuis X4, shoots into one inch easily, at 50 yards, without even trying and without adjusting the barrels. And with a random hand load. Luck? Maybe. Now, I decided to put a different scope on it, one that weighs 5 ounces less than the zeiss with which it shoots the little left and right groups of any number of shots.

Yep, been there done that. However, I would really be interested to see if you could get the same size grouping with the 5 oz. less weight scope by decreasing the velocity of the same projectile by 100 fps.

I find that the smaller the bore diameter is, the more finicky they can be. Larger bores (400, 470, and up...) seem to be more forgiving.

9.3x74r doubles win the award for consistently being the biggest PITA to regulate. As new guy said, smaller calibers are more susceptible to changes than th big guys.

quote:

Originally posted by Aaron Little:
9.3x74r doubles win the award for consistently being the biggest PITA to regulate. As new guy said, smaller calibers are more susceptible to changes than th big guys.

Amen. I just talked to JJ tonight. I am just going to mount the scope I want on my Chapuis, send him the ammo I plan to use and just have the rifle reregulated for the specific configuration I intend to use. Life is too short to frick with it.

My cheap bolt guns seem to be more agreeable. Those fancy big doubles might not...

Once again, it sounds like my exes.

Gents:
Here is my take on the subject.
Cal


Double Rifle Regulation and Accuracy:
Are We Over Thinking the Whole Situation?

text and photos by Cal Pappas

Double rifles have been a big part of my life since the late 1980s. From day one, and remaining constant all these years, have been the tales of double rifles only shooting one bullet weight at one velocity to achieve acceptable accuracy. Some have gone so far to state the bullet shape must be kept to the original. I believed everything I heard along these lines and wrote about it myself. When I started to develop loads for my doubles (beginning with the .500 and .450 black powder express rounds in the late 1980s) I found the best load I held on to that load as if it were gospel. Now, after close to 30 years and having dozens of double rifles pass through my hands (both my own those of friends) I think I have been incorrect in at least some of my beliefs. Allow me to explain some of what I have heard over the years.

First, let's remember the vast majority of double rifle shooting is done with open sights. Off hand or over a rest (standing, seated, or at a bench) two barrels will never shoot as accurately as one barrel. There a too many variables in shooting to make many carved-in-stone statements. The weight and balance of the rifle, the size and experience of the shooter, if the rifle fits well (pull, cast, and drop), if the shooter ingested caffeine or sugar prior to shooting, etc. Some will add temperature, humidity, and elevation to an already complicated list.

So for double rifles, what is acceptable accuracy? In my experience I think if four to six shots that fall in a 2-inch square is outstanding, and within 3 inches acceptable, at 50 yards. I have seen much better groups and many far worse, too. If I can develop my hand loads to fall between 2 and 3 inches I am satisfied.

Here is what I have been told or read and my opinions about such:

Use only one bullet weight:
Easy to understand as well as to do. Just use the same bullet. The .450 to .476 class of nitro cartridges all generated approximately the same energy using a variety of cordite charges to propel bullets of 480, 500 and 520 grains. Higher charges of cordite were used in cases with a larger internal capacity to keep pressures equal. Other bullet weights are used. However, in the 1900 edition of Holland and Holland's catalog, in discussing the new .500-450 nitro express, it is listed as shooting three bullet weights to the same accuracy: 370, 420, 480 grains. The rifles were also constructed to shoot black powder express ammunition accurately!

Only one velocity:
This one concerns me the most. When the regulation facts (or myths?) were standardized (probably the later 1800s), keeping a double rifle to proper regulation the velocity must be kept to the standard load that was used in targeting the rifle. How can this be correct with so many variables? Look at the barrel lengths. Shorter barrels produce less velocity and longer barrels more velocity. In nitro doubles, 24- and 26-inch lengths are the most common but there are many examples with longer and shorter barrels. Even more so in the black powder express rifles. How about the short-barreled howdah rifles that could be 14 to 20 inches? I have never seen the ammo makers (Eley and Kynoch) state on the boxes "for use in 26-inch barrels only." And remember, in order to make their propriety cartridges market with a bit of blue sky in the figures, velocity was often taken from 30-inch barrels.

The 75% rule:
Commonly spoken of today, not so much 20 years ago, the 75% rule is often attributed to Elmer Keith. This magic formula states that with a full powder charge but using a bullet that is 75% (3/4) of the standard weight, acceptable accuracy will be obtained. Elmer may have written about this but it predates Elmer Keith by decades. The 350 Rigby fired a 310 grain bullet at 2000-2150 fps, with 51.5 grains of cordite. This cartridge dates from 1899. In 1908, nine years later, the .350 no2 Rigby fired a 225-grain bullet at 2575 fps with the same cordite charge. The Brits were playing with the 75% rule 100+ years ago! A second example predates the above. In Rigby's 1901 catalog the approximately 3-year old .450 3 1/4" nitro express cartridge is touted. Three bullets of 480-grain weight are listed as is a 350-grain. All are loaded with the same charge of cordite. "The sighting being the same for both within sporting ranges" Holland claims. Again, the (approximately) 75% rule in use in 1901!

The 75% rule in reverse:
In my (limited) experience, accuracy almost as good can he had in a double by using the full bullet weight with 75% of the powder charge. I can't stress enough that if you do this you MUST use a filler to keep the powder next to the primer for proper ignition! You may ask, "Why use the 75% rule in reverse if the original 75% rule works well enough?" The answer is found in a limited supply of bullets for some double rifle calibers. Finding a variety of bullet weights for a .400 or a .450 is easy enough, but near impossible to do so with a .475, .577, or a .600. It is far easier to reduce the powder charge and keep the original bullet weight.

Use one bullet style:
Bullets have made tremendous advancements over the past 40-50 years. Today I feel it a matter of oneupmanship to state one makes a better bullet than a competitor. All are far superior to the construction of the old Kynoch softs and solids. I won't get into the debate of mono metal bullets and OSR (over stressed rifling) here but will state the old rifles should be used with the same ballistics as they were made for in the Victorian and Edwardian eras.

Use one type of powder:
This one can't hold any weight. Today's gunpowder has different characteristics than cordite although some do have similar burn rates. Different charges of smokeless powers will generate the same velocity when adjusted for burn rates (faster powder equals less powder). I have found that using different powders in nitro cases (3031, 4064, 4350, 4831) all will shoot accurately if pressure and velocity are kept to original specifications. Cordite was very sensitive to heat (sun) and black powder was not.

Nitro for Black:
Here's one that will shake the one bullet weight to the core. The most popular example is a .500 bpe charged with approximately 5 drams or 136 grains of Curtis and Harvey's no6 powder and a 340-grain bullet. To produce a good target when these rifles saw the smokeless era, a NFB load was developed. Using 55 grains of the then new cordite and a 440-grain bullet, these rifles shot very well. We won't mention the difference in rifling twist to stabilize the different weight of projectiles. They all shoot well: cordite and black, 340- and 440- grain bullets, the same rifling twist, and a variety of rifle weights and barrel lengths (I've seen .500 bpe barrels from 16 to 30 inches).

One chamber pressure:
Cordite was very sensitive to heat. Tropical climates increased pressure and velocity. The makers in the UK loaded some calibers for a "tropical load" or cordite--55 grains in the .450-400 rather than the standard 60 grains. There are other examples. If a tropical load was used in a moderate climate would accuracy suffer? A few years ago, some mates down under were experimenting with pressure and velocity by adjusting the depth the bullet was seated at. News of this practice stopped so maybe it was not a successful experiment.

Use a standing position only:
Too many variables here for any acceptable standards of accuracy. Off hand shooting is the least accurate and adding a rest brings accuracy into more realistic picture. It has been said that if using a rest one must hold the double rifle as one would when standing and let the rifle recoil as if standing. My best shooting position is seated when over a rest. With my butt as well as both feet on the ground I have a third point to balance on and the rest stabilizes the barrels about as good as can be. (I know bench shooting perhaps is more stable but you don't want to try bench shooting with a 4-bore charged with black powder! I have experimented with shooting from a rest with my front hand between the barrels and the rest and just laying the barrels over the rest. While the double fraternity states the former must be used, I have noticed no difference.

Fire the right barrel first:
Some triggers may have a different weight of pull depending on which barrel fired first. Most hunters and shooters will fire the front trigger and right barrel first. If the game is dropped with the first shot, the barrel is reloaded and the hunt continues. This is evident by the number of vintage doubles on the market with shot out or worn right barrels and the left barrel is in much better to almost new condition. Remember cordite burns very hot, and with corrosive primers barrel wear was common in the old days.

Never lay the barrels directly on a rest:
The barrels must be held in the hand--just ahead of the forend--only. I've heard this for decades and in my shooting my targets don't change if I hold the barrels or lay them on the sand bag rest (or a tree branch whilst hunting).

Wait a specific number of seconds before firing the second barrel:
This one had to be invented by some nimrod trying to create a problem and a solution. Even if true on the bench at the shooting range, no one, and I mean no one will time his shots when hunting anything--deer to elephant.

Muzzle loading double rifles (flint and percussion):
Even more variables as to powder charges in the front stuffers. I have not shot any muzzle loading double rifles but accuracy must remain at an acceptable level as they were common in the 1700s to about the1860s. I've read of the hunters of old pouring an handful of black down the muzzles. No precise measurement of powder weight here for the best accuracy!

How about powder coating?:
In my shooting in 2016 and 2017 I can find absolutely no difference in accuracy or velocity with powdered coated bullets when compared to the same bullet with lubed grooves. I can't comment on paper patching as I have never done that. I have, however, fired grease grooved bullets in rifles specifically made for paper patched bullets (the case contained the original mould) and accuracy was fine. While I do not have a pressure tester the more mundane indicators of high pressure (more recoil, difficulty in opening the action, blowback around the primer, primers pushed back a bit) did not manifest themselves in my shooting.

Doubles all have average accuracy but not outstanding.
This is true when compared to single barrel rifles. But, using open sights in hunting conditions a double's potential will be greater than the average hunter's potential for accuracy. I have read that most hunters can't hit an 8-inch plate at 100 yards off hand. A double will certainly do that. I have also found that the larger the bore, the more forgiving the rifle is to changes of loading. Change my mid-caliber double's load characteristics and targets may change some. Move to a .600 or the 8- and 4-bores, and change the bullet weight by hundreds of grains, and the velocity by 2-300 fps, and they will still shoot the same group size. Remember if a double is too fast it will cross fire and if too slow it will shoot apart (but that is not carved in stone and even more so in the large calibers).

In conclusion, double rifles will shoot fine with a little adjustment to the bullet weight, velocity, and shooting style. No doubt, there are limitations but after nearly 30 years of double rifle shooting I feel the "rules" can be relaxed a bit. The most important thing to remember is to keep pressure (i.e. velocity, bullet diameter and weight) as close as possible to the original cartridge. With all of the above said, I will state when I regulate a double rifle by powder charges, my targets print wide when the bullet is too slow and the projectiles crossfire when shot at a velocity that is too fast. However, when the proper regulation is achieved there may be several reloading variables that will achieve a good target.

Today's black powder does not burn as efficiently as in the days of old so I have found it quite difficult to get my express doubles to shoot well with the same charge of black powder today.

Here's a piece I wrote on the subject, some time ago. Bis repetita placent...

My FN-Browning CCS25 in 9,3x74R rifle left the factory without scope bases and was regulated with iron sights to FN's standards, i.e. 2x2 shots within 5 cm (2") at 80 meters (88 yds). Each bbl. kept its shots touching but I've always been bothered by the "gap" between respective groups. I'll admit it never made a difference in the number of animals killed or missed in drive hunts but then, it's all in the head I know, I'll only be satisfied when both of my bbls. shoot in 1 hole... Later, I had the rifle scoped (bases were hand fitted and silver soldered on the top bbl.).



I can assure you that the newly scoped rifle did need regulating over (I attended the works and after 3-4 sessions of unsoldering - moving wedge in/out - resoldering, I was finally satisfied to see both bbls. making a single hole. Under field conditions (well nearly, I held a stalking stick in my left hand to stabilize), it shoots 2x2 handloads like this at 50 meters :



NB : holding rifle and stick together made the rifle shoot slightly left (most probably because it impedes free swinging under recoil).


I expect some reactions about my possible exaggeration of trivial details, but then, anecdotally, the literature that came with the rifle goes much, much further when describing all conditions which may/will affect bbls. grouping together. Be my guest :

1. bbl. convergence is dictated by many factors. Muzzle jump (different according to ammo used), rifle mass/weight, its center of gravity and balance point (an individual rifle's characteristic). I'll give you one more : each bbl. will/may react with a different torque than its brother. All this explain why only experience and patience will make a competent double rifle regulator and the latter will never be matched by any robot or laser, present or to come ;

2. the rifle is regulated with one kind of ammunition, even a change in production lot may bring changes (it is advised to buy a provision of ammo from the same lot) ;

3. the U bbl. should be fired before the O. Otherwise, the mean POI will be lower than expected ;

4. regulation is attained with both chambers loaded, charging only one barrel may affect results.

All in all, these rifles are no target guns but are meant to be shot under field conditions. Depart from these in any way and you may expose yourself to unpleasant surprises

Great scope there Andre.

Right; any little change can and does change how they shoot, which is my point.
OTOH I mounted a scope on my Krieghoff 450-400 which was not factory regulated for one; it shoots as well or better than the factory regulation target. Showing that the rule is; there are no rules that apply to all double rifles.

And putting up with all that trouble for.....?

quote:

Originally posted by Biebs:
And putting up with all that trouble for.....?

…so we don't have to shoot/own Blasers!
Cal

I don't know anything about this but ask.

Could a barrel be thought of as a box beam?

big caliber fat barrel, less whippy?
smaller caliber small barrel, more whippy

Nope; it ain't just or necessarily, the barrels that are moving; it is the entire platform, meaning the whole rifle. The big calibers do not necessarily have fatter (thicker) barrels. Regulation and points of impact of each barrel is a function of myriad factors, such as muzzle flip and jump, recoil, velocity, even the powder charge and the rate of acceleration the bullet, all affected by how the shooter holds the rifle. and all affect regulation to some degree. Even cadence of firing shots matters.
All this and more, which is what makes shooting double rifles so much fun. And not all of them follow all the rules.
And it's no trouble at all to shoot them.

quote:

Originally posted by cal pappas:

quote:

Originally posted by Biebs:
And putting up with all that trouble for.....?

…so we don't have to shoot/own Blasers!
Cal

AMEN to that..

quote:

quote:
Originally posted by Biebs:
And putting up with all that trouble for.....?



…so we don't have to shoot/own Blasers!
Cal

But just think of the money you'd save! You could use Avery labels for 100 yard targets instead of Hula-Hoops! :-)

Not all Blasers are bad, just the people who shoot them.

I must be reformed! I recently sold my last Blaser, and just bought a fine old British NE double rifle. I guess I'd better order some Rel-15 and some Hula-Hoops! :-)

quote:

Originally posted by Biebs:

quote:

quote:
Originally posted by Biebs:
And putting up with all that trouble for.....?



…so we don't have to shoot/own Blasers!
Cal

But just think of the money you'd save! You could use Avery labels for 100 yard targets instead of Hula-Hoops! :-)

Minute of hula is fine for my 4-bore, Jon.
Cal

Cal, the vacuum alone would kill them as the pound of lead went whizzing by them!

This is a very well "REGULATED" thread, and has just about listed every drawback that any double rifle can have under all circumstances!

Also, there seems to be a rule for everyone to claim doesn't exist, and is simply an excuse for poor shooting by the owner.

The real fact is everyone of the so-called myths are real facts in one rifle or the other.

There is one rule that is constant and always has been since double barreled rifle were made. That is the larger the bore, the less problem one will have finding a regulating load, and on the other end, the smallest, and fastest, chambering in a very light double rifle the regulation will be a real chore to find regulation for.
I talked to a regulator who works for Holland & Holland who told me back in 1964 a customer ordered a double rifle chambered for the new Winchester cartridge the 225 Winchester. That cartridge is a very fast little cartridge, that develops a very sharp recoil and fast barrel time that only moves the barrels a tiny amount during barrel flip. He told me he had a terrible time getting this rifle regulated, and swore he would never again try to regulate a double that light, with a very fast tiny amount of recoil. He said the big bores were a snap to regulate, because of a decent amount of rifle weight, and with a barrel flip that was readily evident!

Cal shoots mostly "BIG BORE" rifles that really need a tow-bar, and wheels and a shooter that is a weight lift champion to lift the cartridges one at a time. That is why he gets a lot of easy loads that regulate. As far as I know his "LITTLE PLINKER" is a 450-400NE that he carries in a shoulder holster rig under his hunting coat, and shoots it with one hand like a pistol.

All kidding aside, the small double rifles like 9.3X74R, and smaller, are often heavily effected by the addition of a scope, rings and bases, than it would be on a larger heavier double. These usually are more effected by two things the weight of the scope and bases, and how heigh the scope is above the barrels, because the flip is changed by these two things.
Todd had a scope mounted on a Chapuis (spl)9.3X74R double the completely destroyed the regulation. He worked for a very long time experimenting with bullets and powders and finally found a load the worked with both scope and irons. The fact is, in most cases like this, a re-regulation is needed to fix.

SOME FOLKS who have never used anything but single barreled rifles think the rules for doubles are the same, and that is why many first time double rifle owners find those rules do not work for doubles. These two are only the same because they are both rifles, but operate by very different rules.

Then there are BLASER owners!!!!!!!!!!!!!!!

Riddle me this: given all the potential factors of getting a double to shoot, how do you work up a load for one? Does the fact that you are regulating the barrels negate the finikiness like we see in a bolt gun regarding powder/oal etc? Is it a matter of getting a bullet to the FPS you want them just send it to JJ? How are both jobs accomplIshed at the same time? Thanks.

quote:

Originally posted by BaxterB:
Riddle me this: given all the potential factors of getting a double to shoot, how do you work up a load for one? Does the fact that you are regulating the barrels negate the finikiness like we see in a bolt gun regarding powder/oal etc? Is it a matter of getting a bullet to the FPS you want them just send it to JJ? How are both jobs accomplIshed at the same time? Thanks.

BAX, if you want a particular load before the rifle is regulated for it, what you do is forget regulation and find a load the prints tight groups from each of the two barrels.
Shoot each barrel like a single shot on it's own target, when you find the load you want shot from each individual barrel, then send the rifle to the smith to regulate the barrels to shoot that load in a composite group.

When properly regulated for that load, the "CENTERS" of each barrels individual groups center will be on it's own side of the aiming point on the target in a composite group of both barrels on the target. A properly regulated will shoot the CENTERS of each barrel
parallel no matter the range, even though the right side of the left group will spill over into the left side of the Right barrels group and vice versa forming a slightly egg shaped composite group of both barrels.

All this is a PERFECT composite group which is only possible if everything is PERFECT! However nothing is always perfect, but in reality one looks for a composite the is as close as he can find. Suffice to say if all bullets were hitting one hole on the target at any range this would mean the rifle was crossing at that range, and would get wider crossed down range. SO what you want to do is look for centers of each barrels individual group to remain on it's own side of the aiming point close enough to make a good composite group of both barrels without the centers crossing.

..........................................................Clear as Mississippi mud, I'm sure!.................

quote:

Originally posted by MacD37:

quote:

Originally posted by BaxterB:
Riddle me this: given all the potential factors of getting a double to shoot, how do you work up a load for one? Does the fact that you are regulating the barrels negate the finikiness like we see in a bolt gun regarding powder/oal etc? Is it a matter of getting a bullet to the FPS you want them just send it to JJ? How are both jobs accomplIshed at the same time? Thanks.

BAX, if you want a particular load before the rifle is regulated for it, what you do is forget regulation and find a load the prints tight groups from each of the two barrels.
Shoot each barrel like a single shot on it's own target, when you find the load you want shot from each individual barrel, then send the rifle to the smith to regulate the barrels to shoot that load in a composite group.

When properly regulated for that load, the "CENTERS" of each barrels individual groups center will be on it's own side of the aiming point on the target in a composite group of both barrels on the target. A properly regulated will shoot the CENTERS of each barrel
parallel no matter the range, even though the right side of the left group will spill over into the left side of the Right barrels group and vice versa forming a slightly egg shaped composite group of both barrels.

All this is a PERFECT composite group which is only possible if everything is PERFECT! However nothing is always perfect, but in reality one looks for a composite the is as close as he can find. Suffice to say if all bullets were hitting one hole on the target at any range this would mean the rifle was crossing at that range, and would get wider crossed down range. SO what you want to do is look for centers of each barrels individual group to remain on it's own side of the aiming point close enough to make a good composite group of both barrels without crossing.

..........................................................Clear as Mississippi mud, I'm sure!.................

Totally clear. I suspected that you would load for each barrel separately but thought that once you began regulating them to each other it might throw the previous work out of the window. Thanks for the detailed explanation.

Don't have a double (yet) but can remember the first time I handled one - permagrin!

Thanks!

Ideally you will know what ammo the rifle was regulated for at the factory and use those. Which may not work either. Loading a separate load for each barrel might work but would not be ideal in the field.
So, working up a load for a rifle for which the regulating load is not known can be very frustrating and sometimes can't be done.
But for new rifles, the factory always tells you the ammo used. Which might not be as good as you think; Most DRs are made in Europe and some use Norma ammo for regulation; not easy to get here and certainly the exact lot is not available. Example, Searcy provides the exact hand load for his rifles and they always hit exactly like they should.
Loading for doubles is not just bullet weight and velocity either; factors such as the type of powder make a world of difference. It's also how the bullets arrive at the velocity that matter too. Flip and jump.
The regulation target described by mac is the ideal; certainly not possible for all rifles. I can show you the factory test targets for some that will never shoot perfectly side by side groups but meet the factory specification and are perfectly usable.
Now, the 9.3 Chapuis I am working with now is not regulated at the factory and soldered together; the barrels are adjustable by the user. Just in this case, it regulates beyond perfectly (sub inch composite groups at 50 yards) from the start, with a load picked at random by me. Luck.
Remember when I said there are no rules? There are rules but every rifle does not follow them.

quote:

Originally posted by cal pappas:

quote:

Originally posted by Biebs:
And putting up with all that trouble for.....?

…so we don't have to shoot/own Blasers!
Cal

Well played; well played...

quote:

Originally posted by BaxterB:

quote:

Originally posted by BaxterB:
Riddle me this: given all the potential factors of getting a double to shoot, how do you work up a load for one? Does the fact that you are regulating the barrels negate the finikiness like we see in a bolt gun regarding powder/oal etc? Is it a matter of getting a bullet to the FPS you want them just send it to JJ? How are both jobs accomplIshed at the same time? Thanks.

Totally clear. I suspected that you would load for each barrel separately but thought that once you began regulating them to each other it might throw the previous work out of the window. Thanks for the detailed explanation.

Don't have a double (yet) but can remember the first time I handled one - permagrin!

I think you may have misunderstood my meaning of working up a load that shoots good groups in both barrels regardless of where they are on the target. The smith will use that load to regulate the barrels to bring both barrels shooting into the same composite group.

All the load for the barrels is finding a load the shoots well in either barrel (same load for both barrels) All that does is find a load the shoots in both barrels. The regulation of the barrels will not change that. Once regulated with that load it will shoot to regulation with that load.

.......................................................................

quote:

Originally posted by MacD37:

quote:

Originally posted by BaxterB:

quote:

Originally posted by BaxterB:
Riddle me this: given all the potential factors of getting a double to shoot, how do you work up a load for one? Does the fact that you are regulating the barrels negate the finikiness like we see in a bolt gun regarding powder/oal etc? Is it a matter of getting a bullet to the FPS you want them just send it to JJ? How are both jobs accomplIshed at the same time? Thanks.

Totally clear. I suspected that you would load for each barrel separately but thought that once you began regulating them to each other it might throw the previous work out of the window. Thanks for the detailed explanation.

Don't have a double (yet) but can remember the first time I handled one - permagrin!

I think you may have misunderstood my meaning of working up a load that shoots good groups in both barrels regardless of where they are on the target. The smith will use that load to regulate the barrels to bring both barrels shooting into the same composite group.

All the load for the barrels is finding a load the shoots well in either barrel (same load for both barrels) All that does is find a load the shoots in both barrels. The regulation of the barrels will not change that. Once regulated with that load it will shoot to regulation with that load.

.......................................................................

I get it, I’m just surprised that after you find the same load that works in both barrels and you sent the rifle to be regulated, messing with the barrels’ orientation to each other to get it regulated ALSO doesn’t mess with how those loads performed.