Sabatti double rifles

CTDolan

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As a general rule of thumb, with common NE calibers, SxS rifle barrels are set to converge 0.003"-0.005" per inch of barrel length. This is the starting point and the degree of convergence which should be in place whether doing up a monoblock, a chopper lump, or any other joining system. Regulation is then a matter of making very minor adjustments, not bending the tubes.
 

CTDolan

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By the way, this rule holds because as the caliber (recoil) goes up, so does the weight of the double. And, as you know, all bullets from NE rounds exit at approximately the same velocity, so barrel time is pretty much a constant.
 

johneracer

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Thank you for good info. I am one of the people that is fascinated by all aspects of shooting, so the physics of how and why intrigue me. Great info
 

sestoppelman

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Thanks CT! I confess to knowing near nothing about a fine double other than that they are quite expensive.
 

edward

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DUGABOY1

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Gentlemen, I did not mean to start a crap fest here! All I am doing is making you aware of the facts. You are free to believe them or not, but until you do you will never understand how a double rifle works. You would not believe the number of double rifles I have bought because a guy bought a double and couldn’t make it shoot right, and thought they had bought a bad rifle.


Because a double was regulated with a certain factory ammo doesn’t mean it will shoot with that factory forever. Little things like different powder lots can cause a need for adjusting the load to fit the built in regulation. It is my experience that the only way to get the best from a double rifle is by understanding how regulations works, and how to hand load to restore proper composite groups. If a double rifles’ barrels are shooting too wide, the load is too slow, if crossing the load is too fast.


As I said before what you are regulating is the centers of each barrels’ individual groups to place that CENTER on it’s own side of the aiming point by an amount equal to half the distance between the CENTERS of each barrels individual bore.


Certainly the bullets on the LEFT side of the RIGHT barrels’ group will spill over into the RIGHT side of the LEFT barrels’group.


The bullets on the RIGHT side of the LEFT barels’group will spill over into the LEFT side of the RIGHT barrels group. That is called a COMPOSITE GROUP of both barrels.


But when properly regulated the CENTERS of each barrel will remain on it’s own side of the aiming point and the combined group of both barrels will be a slightly oval shaped COMPOSITE GROUP of both barrels along a horizontal line through the aiming point.


So if both barrels are shooting a one inch individual group the composite group of both barrels will a mix of approximately 3 to 3 and one half inches wide, and one to 1 to 1 and one half top to bottom of the group using the 50 yd sight.


There is a perfectly valid reason the barrels on a double rifle are soldered to converge. The reason is a thing called barrel time and recoil flip that makes this convergence necessary!


That reason is because a side by side double rifle has to be soldered converging so the rifle will shoot side by side. Now I know that sounds like nonsense, but it is fact. There are physical reasons for this need.


When the RIGHT barrel is fired with the sights pointed dead on the center of the bull on the target the line of sight through the RIGHT barrel is pointing to a spot on the target that is LOW and LEFT of the aiming point. The right barrel will move BACK, UP and AWAY from the left barrel(to the RIGHT)

The barrel time is the time the bullet is moving down the bore to the muzzle. The regulation is adjusted to have right barrel pointing at the place where the sight was on the target when the trigger was pulled when the bullet exits the muzzle. The exact opposite happens for the left barrel by an equal amount when that bullets exits its’ muzzle. This is how a double rifle is regulated by trial and error.


If you don’t believe this to be true, then take the barrels off you double and place them in a padded vice. Adjust the barrels so the sights are pointing to the aiming point at the distance engraved on the back sight. Now, take a pair of empty cases and pop the primers out and place them in the chambers. Use the primer holes like a peep sight and look at that target through the bores of each barrel. What you will see is, the RIGHT barrel will be pointing to place on the target that is LOW, and on the LEFT of the aiming point. Now, look through the case of the LEFT barrel, and what you will see is the LEFT barrel will be looking at a place that is on the RIGHT and LOW of the aiming point.


Because the barrels are physically converging is one reason folks who don’t know better think a double rifle is regulated to cross, that and the factories’ habit of using the same word for stating how the sights are filed. That word is REGULATE. In regard to the sights to regulate simply means the distance the sight is filed for. It doesn’t mean the rifle crosses at that range. It simply means the rifle will form a composite group at that range when that sight is used. The regulating of the sights and regulating of the barrels are two entirely different things.


To answer the confusion about the word INFINITY. The rifle has its’ own infinity which is the effective range of the caliber of the rifle. No rifle of any kind will shoot any bullet to infinity in the normal meaning of the word. The curvature of the earth would stop that if nothing else.


The mistake is made all the time by folks who are new to double rifles of thinking all one has to do is make the barrels side by side with the use of a laser to make the rifle shoot side by side. They say then the doubles could be made like any cheap bolt action, but sorry that will not work. Done that way the rifle would shoot very wide. The reason is because of the way a double rifle recoils during BARREL TIME.
 

sestoppelman

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I don't think anyone would accuse you of starting a crap fest. Only one poster said anything silly in my view, not helpful. I appreciate your concise descriptions on the ways of the DR. Thanks!!
 

Heym 88

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Duggaboy I remember you posted something like this a long time ago. It has served me well in explaining to others how a double rifle works. Thanks for posting this so others can learn as well.
 

johneracer

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Lots of good info, yes we agree with your statements so no you did not start a crap fest. That info will help anyone that is getting into double rifles not rush off and think the rifle is crap and not shooting well. If the left barrel is shooting 1.5 inch groups at 50 and so is the right, then you could have spread of converging to 3 inches. The important part is like you stated to find the center of multiple shots and use that instead of a single shot
 

DUGABOY1

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Thanks guys! Hope any of this helps.:Peeking:
 

edward

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when i bought mine,3500-5000 was the price in 2012. ive posted this before but will again.this is a 50 yard target,upper right groups are right barrel,lower left are left barrel.two tightest shots are with the hornady 286 gr softs the gun was regulated with.the wider two shots are with hydro solids hand loads.my eyes require i use a srs1 red dot.

View attachment 57766 View attachment 57767
duggaboy, how much better than this do you want ?
 

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