doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com What is the ideal convergance of SXS barrels?

Vol423,
It was I believe standard practice in the British gun trade to set the convergence of 12G barrels at 40 yards. Packing blocks are made to space the barrels during the manufacturing process so as to guarantee the point of impact.
In the case of the double rifle, in particular large calibre ,the point of impact was set at 100 yards. Once again guaranteed by the use of packing blocks during manufacture.
[IE: I recognise that in the case of the double rifle regulation may be required despite the use of packing blocks]
I recall that years ago when visiting H&H they had on display a very large block of teak sectioned to show two bullets entering the block and impacting on one another.The bullets were said to be fired from a fixed bench rest at 100 yards.

Roy;
Don't want to seem overly picky but the first part of your statement doesn't jive with the 2nd part. The bbls themselves were Not set to converge at 40yds, they were set to have the patterns impact together at 40yds. As has been well pointed out by several in this long thread the bbl's axis themselves are set to converge very close to 2 yds (between 6&7 feet).

I'm thinking that I would not want to shoot a 1 3/4 oz load in a sub-6# gun. Flinch city, here we come!

Maybe a .75 oz load?

Larry ya gotta be careful with that quote and paste stuff; that ain't my words. I would not want to suffer the recoil of that load either...Geo

2-piper
Recommend that you refer to "The Modern Shotgun,"Vol,1 by Major Sir G Burrard, pages 31-35. These pages review the need for shotgun barrels to converge at 40 Yards so as to hit at the same spot. Also seen are illustrations of correctly designed barrel spacers.
William Greener in his book, "The Gun" 1834,also discusses the need for shotgun barrels to Converge.

Roy, you're missing a difference in careful definition of terms -- barrel convergence being where the bore lines cross, not where shot patterns hit. Burrard may not have made the distinction, but it's been drawn in this thread. Jay

This topic reminds me of the patterning thread in some ways.

The convergence of a production gun is done by dimensional control of what the maker developed and validated on a prototype just as virtually all chokes in production guns are machined to dimensional specification rather than individually tested and developed.

The maker chose the load for convergence testing and also chose the shooter(s), whose individual physical characteristics can affect POI. Even the H&H video showed an employee shooting for POI rather than the customer of the bespoke gun. It must work out well a high percentage of the time or they'd do it differently. But there was a recent post about a bespoke gun that hit off target by enough to perturb the customer.

If the POIs remained parallel out to infinity that would be just as acceptable as them converging at 40 yards. What is the difference in the muzzle centerlines of a 12 gauge SxS - 0.9 inches?

I used the "Shotgun Insight" program to anyalyze somewhere around 200 patterns, including POI. I shot 20 rounds out of each barrel freehand. The average POIs for each barrel were typically a minimum of 6" apart at 40 yards, both for SxSs and OUs. It is also very likely two shooters shooting the same gun would get different POIs.

There is no inherent need for convergence of the POIs at 40 yards. And divergence is probably the norm.

Best,

Mike

Sorry about that, George. You'd responded to Coosa, who was the guy who said he used the 1 3/4 oz load.