SXS Question

[vitesse9]

I have a stoeger coach gun. It's actually the second one because the first had to go back to the factory and was replaced.

On the first one, the right bbl was dead on, but the left bbl was about 2.5 inches high and 2.5 inches left. Sent the first gun back and Stoeger sent a new one.

On the second one, the right bbl is dead on on elevation and about 2 inches right on windage. The left bbl is about 1 inch high in elevation and about two inches left in windage. All patterning was done at 15 yards.

BTW, these are the supreme models and thus have chokes. I went out and purchased two IC aftermarket chokes of the same brand and patterning was about the same.

This is my first SXS. I guess I expected windage to be a little different becasuse the bbls are, well, side by side. However, I'm concerned about the difference in elevation b/w the two bbls (left bbl is about an inch higher at 15 yards).

Any thoughts?

[Bill DeShivs]

They are shotguns, not slug guns.

[darkgael]

"On the second one, the right bbl is dead on on elevation and about 2 inches right on windage. The left bbl is about 1 inch high in elevation and about two inches left in windage. All patterning was done at 15 yards."
What gauge? What load? Shot? Slugs?
Usually, patterning is done at 40 yards. I'm wondering how you can be as exact about windage and elevation as you are stating.....inches. When you state those measurements, are you referring to the center of the pattern? Most patterning - could be my own experience only - is done to determine the density of the shot pattern at a given distance with a given choke and load, not so much to determine windage and elevation. If you are expecting the barrels to be regulated like they would be on a double rifle, they are not.
Pete

[zippy13]

Originally Posted by vitesse9

SXS Question
I have a stoeger coach gun...
...I'm concerned about the difference in elevation b/w the two bbls (left bbl is about an inch higher at 15 yards).

Any thoughts?

You didn't describe your testing procedures, so an evaluation isn't appropriate. If you're really concerned, contact Stoeger and ask them about their performance standards for your model. You'll probably find yours is well within their specs.

[vitesse9]

Perhaps patterning is not the right term. Maybe sighting is more accurate. My proceedure was as follows:

Offhand at 15 yards with the same brand and lot of rifled slugs in each bbl. That's how I evaluated the basic windage and elevation.

Then, I used the same brand and lot of 00 buck at the same distance. Ended up getting the same basic "pattern": i.e. a hand sized pattern from the shot about 2 inches to the right out of the right bbl. and about dead on in elevation. From the left bbl. a hand-sized pattern about two inches to the left and about an inch higher than the right bbl. Measurements were approximate, of course, but my conclusion was that the point of impact from the left bbl. was certainly higher than the right bbl.

When measuring the slugs, I treated them like bullets. When measuring the shot patterns, I measured from the middle of the pattern in approximating windage and elevation.

[darkgael]

Vitesse: Thanks for the additional info. That is actually very good for slugs in a SXS. Indeed, given what you are shooting, there was nothing wrong with the gun that you sent back to Stoeger.
Remember....A SXS is not a double rifle where the barrels are "regulated" to put slugs together at a specific distance. With DRs the distance is anywhere from 50 to 100 yards (or more, depending on the gun. I have a DR 30-06 that will keep both shots in the kill zone of a deer out to 200 or so yards.)
Try the SXS at what you expect your hunting distance to be. I have done what you are doing with a couple of SXS, just to see, and they are about what yours is doing at 15 yards. At 50, the barrels are quite far apart.
Pete

[zippy13]

If it ain't broke, don't fix it.

When evaluating your off-hand testing, don't forget: Double guns (SxS's) have a lateral eccentricity that's a component of the recoil dynamics.

[vitesse9]

Thanks for all of the advice.

[darkgael]

Zippy: "Double guns (SxS's) have a lateral eccentricity that's a component of the recoil dynamics."
Ok. You've piqued my interest but you are gonna have to say that in simpler terms. would you rephrase that for a simple soul? Thanks.
Pete

[zippy13]

Originally Posted by darkgael

Zippy: "Double guns (SxS's) have a lateral eccentricity that's a component of the recoil dynamics."
Ok. You've piqued my interest but you are gonna have to say that in simpler terms. would you rephrase that for a simple soul?
Thanks.
Pete

Okay, Pete, I'll give it a go...

Recoil keeps reminding us, when a firearm discharges the laws of physics come into play. Action and reaction -- applied forces and resistive forces. The applied force is the easy part (it's covered in a topic we know as internal ballistics) since it acts in-line with the barrel. However, the resistive forces are not so simple. With a typical stance (no barrels between the toes) the hands, cheek and shoulder each provide components of the resistive force. Shooters of different sizes and weights will distribute the individual resistive components differently -- so will different stock dimensions. To keep the ghost of Sir Issac Newton happy, the combination of the resistive forces will equal the applied force. If the combination of all the restive force components is also in-line with the bore, then the motion under recoil will be straight back and forth (perfect reciprocation). Yet, we're all aware that this isn't the case, the motion is back and upward... why?

Look at a typical rifle, or shotgun, and its shape tells you that the center of the reactive forces is below the barrel's axis. This dimensional difference is known as vertical eccentricity. When opposing forces are eccentric, a rotational force, known as a couple is created. It's this couple that causes the barrel lift we're all familiar with.

The greater this vertical eccentricity, the more the muzzle will rise. This is why it's important when shooting an O/U that the lower barrel be shot first. It has lesser eccentricity than the upper barrel. So, it lifts less and you get on your second target quicker than if you shot the upper barrel first.

A benefit of SxS geometry is that both barrels have the same vertical eccentricity. So lift is the same for either barrel -- an advantage over the O/U configuration. However, the SxS brings in another factor: lateral, or horizontal eccentricity. For the sake of discussion, let's assume the center of the resistive forces is in line with the SxS's center rib. So, now we've added a lateral component to the couple. Since the lateral eccentricity is less than the vertical, you might not notice the left or right components of barrel lift. And, since you're usually swinging a shotgun, the lateral part becomes almost inconsequential.

In reality, SxS shooter's resistive forces may not be centered on the rib, and will change each time the gun is mounted. If the resistive forces are centered behind the right barrel, then only the left will have a lateral component to the lifting couple. In this condition, the right barrel will lift without a horizontal component, and the left's horizontal component will double. Don't worry, in the greater scheme of things, these SxS lateral forces are minor, won't change your shooting style, but should be understood.

Remember what vitesse9 said about his off-hand testing: "...the right bbl is dead on on elevation and about 2 inches right on windage. The left bbl is about 1 inch high in elevation and about two inches left in windage." How can we determine what might be due to an inconsistent mount? That's why I said: When evaluating your off-hand testing, don't forget: Double guns (SxS's) have a lateral eccentricity that's a component of the recoil dynamics. To test how the gun shoots, you really need a more uniform resistive force obtainable only with a rest.