doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Inherent inaccuracy of a SXS-How Much?

I am not addressing what physics are involved or the convergence rate of the barrels. Just "If the barrel centerlines are .85" apart and POIs converge at 40 yards, then halfway (20 yards) the POIs will be .425" apart. At 60 yeards they will also be .425" apart." I believe that is a fact of geometry.

I repeat, .425" at 20 yards and 60 yards is closer than I can hold the gun to or even see.

Best,

Mike

What about barrel time and the effect of recoil on the P.O.I.?

A lighter payload at a faster speed will have less time in the barrel than a heavier payload at a slower speed. So wouldn't the dynamics of the barrel's movement impact the P.O.I.

Seems these variances between the barrels would be more difficult to manage with a double rather than with a single barrel shotgun.

Hal,
It does impact the POI and it is more difficult to manage than a single barrel gun, as illustrated by some recent POI problems related by other members recently, where stock bending and other methods had to be employed to bring a gun to shoot both barrels acceptably to point of aim.

The ultimate will be the last target for 200x200 at the world FITASC championship....the others have been done.

I used to fly sailplanes. Every landing I made was "dead stick". BFD guess it's all a matter of perspective.

Dr.WtS

Chuck:

I think there is a message for you in 5 dead engine landings .......with over 20,000 hours I've yet to make an unintentional dead stick landing......from large jets to J-3's........and everything in between.........

Made many intentional dead stick landings (zero thrust) as an IP and line pilot in the Navy and also as a civilian airline, CFII and check pilot.....

If you were a Democrat I could understand it......?......

Mike;
I will say this as nice as I know how, but the situation you describe simply does not exist. If you insist on ignoring the dynamics then it becomes necessary to extend your lines rearward for the length of the bbl. Assume 30" bbls then it would be found the bores there would be seperated by only .868". With chamber dia's of .813 at rear this would only leave a web of .055" between the tubes. Two shells I picked up at random 1-AA & 1-RXP both had rims which mic'd to .880" thus two shells could not even be chambered side by side as they would overlap.
Fact Is; The bbls do converge from breech to muzzle. L C Smith specs as I pointed out said .011" per inch. Some Lefevers I carefully measured had virtually identical convergence. They do so at a constant rate for their entire length, they do not converge quicker near the breech & then "Bend" back to near parallel as they approaxch the muzzle. Using that .011" figure with an .850" muzzle spacing would give a breech spacing of 1.180". This is certainly a realistic figure.
To extend those lines from a static position & using the .850" muzzle seperation then the two charges would hit together at 6' 5¼" & at 40 yds would hit 15" apart, opposite of which bbl they were fired from.
This is Not the Situation which Actually Exists
Assume the sight line bisects the angle between the two bbls & is on target when the trigger is pulled (for the right bbl). By the time the shot has reached the muzzle the bbls will have moved slightly Back, Up, & to the Right. Again on the assumption the guns regulation hits POA at 40 yds the bore axis will be pointed at the center of the 40 yd target, but the sight line will point some 7½" to the right of it.
The muzzles will of course still be .850" apart, but the axis of the left bbl will be pointing some 15" to the right of the target. That .425" at 20 yds just completely vanished from the picture.
It does not take a great deal of movement to bring about this "New" alignment, but it dafinitely cannot be stated that it will be at exactly half the muzzle spacing when the shot leaves the bbls.

Could someone please provide an opinion of the magnitude of lateral displacement during "barrel time" due to cast. G. T. Garwood made much of the "fact" that a stock doglegged to the right (cast off) will tend to decrease lateral displacement of right barrel to right hand side and increase lateral displacement of the left to left hand. I have always assumed that a cast off stock gave a "natural" lead on a right to left crossing target particularly with the left barrel. Is that indeed the case? If such effects of cast are appreciable, a crossover stock should produce a relatively large lateral displacement of both barrels and would seem to me to demand some compensation in the view of the old target/muzzle or target/pointin finger relationship. What say all of Ye?

jack

I think you need to go shooting

Possibly but don't quote me on that. Pretty hot for Weds nite skeet or trap; maybe Sunday if this weather blows out.

jack