Hello, all of you

I would like to know your opinion/experience regarding action looseness and its effects over regulation. I have read somewhere that a double will not regulate correctly if the action is loose, and in other place(s) that action looseness will not have a measurable effect over it. My theoretical calculations are as follows: Imagine (The Lord will not let it happen...!) that your double has a worn hinge pin, and you have a fore/aft play of, say, one thousandth of an inch betwwen the action and the barrels. With an action width of say 1,5" and a barrel length of 26", the muzzle end of the barrels can move about 35 thousands (the distance between the center of the barrel and the center of the action is less than half the width of the action). At 50 yards, this movement corresponds with nearly 2,5 inches of outward movement of each barrel, or a theorical movement between the two bullets of (aargh...) of five inches more that what the regulator planned. If you fix the rifle and tighten the action, this barrel movement is not more possible, so the double will regulate different (hopefully, as the regulator planned)
Any of you has had some experience of changes in the regulation of a "off face" double after being tightened? What do you think about it?

Thank you

Antonio

Can't say much on what you are asking as if I ever came across a DR that
I purchased that was loose, I had it tightened and brought up to spec before
shooting it.

I will say that loose ribs can have a big effect on Regulation.

.

I don't know about your theoretical measurements, but IMO a loose "OFF FACE" double rifle could certainly have an adverse effect on regulation! However where double rifle repaires are concerned, the cost of putting the rifle back on face is comparitively cheap!

A double rifle MUST be tight on face to be effectively regulated. If loose/ off face, a D/R will usually shoot inconsistantly. The only way to achieve consistant groups for regulation is to have the action tight and barrels and ribs properly soldered.
After tightening the barrels and action, the groups will invariably change position (usually by several inches) and will become more consistant in their placement.
John Maples

off -face = unsafe

and yes, it wont' regulate properly

getting one on face is not rocket surgery

Thank you for your advises regarding the safety (or lack of it) of a worn double. When I ask if someone has some experience with a off face double is to confirm if the aforementioned theory and table calculations are true and if tightening the rifle really makes a "shooting apart" double in one with better regulation.

Three years ago I got a nice Auguste Francotte in 450 BP for a nice price. The rifle was clearly off face,and shot something like a foot apart at 50 yards. The hook and the bites were fixed, a good load was developed, and now it shoots 2-3" apart at 50 yards. So far, my theory is correct. But in my other life I am a medical doctor, my work is usually considered as "scientific" and a scientific paper with a number of subjects equal to "one" is considered as "low statistical significance"...
Really, no one of you has tightened a double and seen changes in the shooting?

Thank you

Antonio

antonio .. i have tighted shoties that became double rifles when i built them ...

if you have a loose scope mount, do you expect it to group?

herrdoktor

The quickest way to make a double even more off the face is to shoot it when it is loose.
And this can then cause uneven wear / damage.

As I said before, if I buy a gun that is loose,
it gets fixed up BEFORE I shoot it for groups. (I shoot it 2 - 4 times to see if any firing pin or trigger / safety issues are evident).

Then off to the gunsmith.

.

How exactly is the rifle brought "on face"? In laymans terms,please, I am no engineer. Asking because a 475 no2 francotte I love is not on face, and I WANT IT if it can be fixed safely and relatively inexpensively

Depends partly on why it is off face but the ways I know of are (this is NOT to say that these are the recommended methods:-

1.Replace the hinge pin (not always possible ie Webley actions)
2. Use a thin metal sleeve or bearing on the inside of the hook
3. Insert a wedge into the inside of the hook
which is made of harder metal than the wedge.
4. Build up the hook by Tig welding or some other method. I believe some hinge pins have also been built up this way.


I am sure others will add a few more and / or more detail.

.

The simplest fix is to simply re-index the hinge pin. It only wears on the bearing surfice and you have brand new 180 degrese away.

quote:

Originally posted by Akshooter:
The simplest fix is to simply re-index the hinge pin. It only wears on the bearing surfice and you have brand new 180 degrese away.

I'm not a DR shooter but with my Miroku O/U shotgun which has shot thousands upon thousands of rounds on competition and game, I have always had a small syringe filled with the highest quality EP grease and the last thing I do on assembly after cleaning everytime the gun is used, is to apply a dob in the hook and on the bearing surfaces between the fore-end and the action. The action is as tight as the day it left the factory.

As identified here, coming off the face is most always due to wear on the pin and hook. Prevent the wear and the rifle will stay on face. Steel will not wear if it has a lubed bearing surface.

The old steels will streach though and wear some with 100 years of service. Lube isn't the only answer though it helps alot.

quote:

Originally posted by emron:
How exactly is the rifle brought "on face"? In laymans terms,please, I am no engineer. Asking because a 475 no2 francotte I love is not on face, and I WANT IT if it can be fixed safely and relatively inexpensively

The best way to have your 475 no2 francotte repaired is to ship it to Champlin Firearms att. JJ Perodeau.
Bill

I think the best method of retightening a double, if possible, is making a new hinge pin of the correct hardness and of a little bigger diameter, a very few thousands of an inch. This will move the barrels backwards, correctly against the face of the action, and also move the lugs so they interact with the slide which runs inside the action under the barrels flat the way it should (excuse me if I don´t use the exact words, please...). Sometimes the slide needs some material built up and file adjusted so it makes full contact with both lugs.
I have never seen a "thin metal sheet" welded inside the hook. The correct thickness would be too thin, in the order of thousandths of an inch, welding included. It is much esasier the Tig welding inside the hook 500N mentions.
If you can find a good gunsmith, it is possible to have your double retightened at a reasonable cost.
I will not mentions the "dirty tricks" like peening or pressing the hook... that will not work more than a few shots.

Antonio

quote:

Originally posted by herrdoktor:

I will not mentions the "dirty tricks" like peening or pressing the hook... that will not work more than a few shots.

Antonio

Funny you mention that.

I was going to put the unscrupulous method of back yard gunsmiths who
use the Vice but deleted it before posting.

IMHO, it is always worth checking the hooks of any shotgun and DR barrels
for tell tale marks, especially on old guns.

.

An off face double at some point will lose its accuracy and probably shoot larger groups..barrels coming unsoldered will ruin both.
A slightly off face gun won't be much of a problem, but will become increasing worse in time. When it quits shooting is anybodys guess.

To see if your gun is off face, take off the forend and see how much play is in the barrel to action juncture. There is usually a tad in most doubles.

quote:

Originally posted by Mike Brooks:
The old steels will streach though and wear some with 100 years of service. Lube isn't the only answer though it helps alot.

That is true and that's why I said coming off the face is almost always due to wear on the pin and/or hook surface. Just re-indexing the existing pin or replacing it with another of the same size won't always work.
I wonder why nobody has come up with a camming pin arrangement, probably not practical considering the few thou we are usually talking when off the face.

quote:

Originally posted by eagle27:
I wonder why nobody has come up with a camming pin arrangement, probably not practical considering the few thou we are usually talking when off the face.

The Webley Screw Grip goes some way to overcoming a loose gun by the way it works.

.

quote:

I wonder why nobody has come up with a camming pin arrangement, probably not practical considering the few thou we are usually talking when off the face

In many cases hinge pins are tappered so reindexing them dose have somewhat of a cam effect.

eagle27 Your idea of a cam is a good one I have pondered that very thing myself. Some high end Germand scope mounts have this very same idea too allow for wear.

Akshooter:
The idea of a hinge pin arranged as a cam is interesting, and, as you mentioned, German mounts, specifically EAW Apel, have a cammed pin to adjust the rear base in place; but that cam is arranged in the same direction of the barrel and do not suffer from recoil. I think a cammed hinge pin in a double would move under recoil and you would have "automatic off face" in a few shots. A hinge pin of the correct size and esay to machine and install should be simpler and better.

Lefever took care of it with a ball joint. Still unique after all this time.

quote:

Originally posted by herrdoktor:
Akshooter:
The idea of a hinge pin arranged as a cam is interesting, and, as you mentioned, German mounts, specifically EAW Apel, have a cammed pin to adjust the rear base in place; but that cam is arranged in the same direction of the barrel and do not suffer from recoil. I think a cammed hinge pin in a double would move under recoil and you would have "automatic off face" in a few shots. A hinge pin of the correct size and esay to machine and install should be simpler and better.

I am wondering what you have done to repair your rifle.
Bill