Couple Barrel Questions

[Matt Valinsky]

In doing some reading about barrels on SxS guns, they talk about the centerline of the barrels converging some distance from the muzzle. With Parkers, what generally would that distance be? Or, did it vary by gage, choke, barrel length or all of the above?

Also, is there a typical choke length or did that vary? How is that determined so one might know if a barrel had been cut back?

Just stuff a new guy would like to know.

Thanks much. Matt

[Bruce Day]

Matt, your post has been here a while with no responses, so here goes what I know. I am limited to Parkers, can't answer for others, and this is a PArker forum.

Choke lengths: in Parkers 2" to 4". 2 1/2 to 3 is common, and varies by amount of constriction.

Convergence: Its not like a double rifle set up to shoot to the same 1" at some distance. Shotguns are set up to deliver most of their shot in a 30" circle at some yards distance. 40 yards is standard patterning distance but some meant for close shooting were patterned at 25 or 30 yards. The less constriction the bigger the spread but what Parker called the killing circle is defined as a 30 " circle , or effective "pattern". You can attempt to determine the distance of convergence by sighting through the centerpoint of each bore. Ideally you should be able to sight down the rib and the shot pattern from both barrels should be centered in the same circle. However, some trap guns, including Parker trap guns, shoot higher than the aiming point; a built in lead for a rising target.

Its an interesting question, I've never been inclined to sight through mine and find out. Probably wouldn't make a bit of difference.....I can't hit anything anyway.

Maybe some shotgun ballistics experts will chime in now that I've got it started.

[Kensal Rise]

Matt:
All of the things you ask about depend GREATLY on many things. Just some are:
1) the quality of the barrels and their assembly
2) the quality and care put into their boring
3) the stock and its dimensions
4) the shooter him or herself

Bottom line: A SxS double is supposed to converge. But exactly where and how effectively it does can only be determined by shooting it. Yourself. Repeatedly.

Best, Kensal

[Matt Valinsky]

This afternoon I had the chance to do a little calculating on barrel centerline angles in relationship to the centerline of the rib for the barrel centerlines to converge at 40 yards. Interesting what a little math will tell you to debunk what you think your eyes are telling you and what I thought was happening.

I also plotted the published percentage of shot on a 30" target at 40 yards for full, modified and cylinder chokes and compared that with the published info of effective range for each choke and the published pattern percentages at those ranges.

Also took a gander at what ranges in yards 100 percent of the shot would remain witin the 30 " target.

Interesting stuff, at least for me and helped me to understand my first question. Guess I should have thought about it some before I asked.

Now I have to figure out Kensal's response #3 and how it fits into the equation.

Kensal, jump right in if you feel inclined.

Amazing what a guy can think about sitting at the office with absolutely nothing to do thanks to the wonderful economey waiting for 2/28 to roll around.

[John Taddeo]

Would the centerline question be similar or maybe the same issue as "point of impact" found when patterning an over and under for Trap or skeet , which is usually compensated by comb ajustment? I would think a P.O.convergence could be found by using two laser bore sighters (generally for slug barrels) and find the distance at which the two dots might intersect on a patterning target. I have heard a few shooters complain that of their high end multi barrel sets not having the same convergence point. The o\u gun would change the target floating point if the clay is shot at the same distance. I would think a sxs is a lead and distance issue if one wants to center the target. Amazing how we miss a target with a 30" diam. pattern of flying lead , isn't it? I believe modern manufactured guns are "supposed" to converge at 40 yds. It would be interesting to know what the Parker standard was. I think that was before I.S.O 9000.

[Kensal Rise]

Matt:
Much of your calculations have have already been reasoned out in:

The Mysteries of Shotgun Patterns by Oberfell and Thompson.

I recommend a copy.

And... how the stock fits -- or doesn't -- a person will alter the POI as indicated above. So will the load, shot size, etc. Lasers will only show you where the gun points with a laser -- not necessairly with a fired shot cartridge. It's a maddening game. Best to stick with one gun and get used to it if that's a concern.

Best, Kensal

[John Taddeo]

Shooting one gun and knowing where it hits with each load is by far the only way to go. The only problem is there are so many guns out there in need of a good home, and I can't help but feel obligated to help all I can.

[Autumn Daze]

Stick to one gun?? Oh hell no.....

[ed good]

daze: im wid you...shooting only one gun takes away one of our major excuses for missing...

i have several others, but would like to hear yours first.

[Matt Valinsky]

Having never shot Trap, Skeet or Sporting Clays and getting ready to give it a try, share those excuses, please! I believe I'm gonna need them.