doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com What's the biggest problem ..........updated

Since the question starts with the potential buyer "wanting" a double gun, the pool is limited.

I'd say the biggest "problem" facing a potential buyer is justifying the purchase.
Whether it's cost or utility.

There are fabulous guns out there at several price points that will function in casual use for decades.

For a dedicated shooter, not so much.
So, service availability is a real issue. They are going to break in heavy use.

Stan is right.

In the mass production world, products are sold that are simply defective because of lack of effort on the part of the manufacturer.

Barrel sets that are simply brazed up in a jig are not 'regulated'. 'Regulation' is a process whereby a gun maker adjusts his product to shoot to point of aim with a specific load.

Patterns do not 'converge'. Barrels converge at the muzzle to make the axes of the bores and thus the flight paths of the shot clouds parallel to each other at bore exit.

A shotgun is a second class lever like a wheelbarrow. Forces during barrel travel cause torque. 'Convergence' compensates for the torque and points the gun at the aiming point at bore exit.

Ideal regulation results in patterns that have centers the same distance apart from the muzzle to infinity. That distance apart is the same as the distance between the muzzles, and is so small that it just gets lost in the noise. Observable cross firing at any distance is an error.

A cursory search found this thread:

http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=88393&page=1

Pay particular attention to the posts of Jim Legg and 2-Piper.

Are shotgunjones and I the only two shooters on earth that understand that "there is no converging of a shotgun pattern"? There is no convergence simply because the distance from bore center to rib center is less than a half inch. Someone may claim to know what the difference is in two patterns with centers a half inch apart, but I sure can't see that difference.

I'm here mostly for what I learn about shotguns and what others do and think about them. Thank you.

As an amplification -

Suppose a well-heeled man places an order with (insert favorite custom shotgun maker here).

They ask him which load he wants the gun to be regulated with.

Seriously, they do. If they forget to ask, the customer should tell them. He should fully expect that for his (insert vast sum here) and several year wait that the gun should shoot as specified.

Now, suppose the load chosen was the classic 1 1/16 oz. 1250 fps Eley Grand Prix.

Should our sport now choose to warm up for the season with the ever popular 7/8 oz. hand load that the books all run at 1300 fps he should not be shocked when the gun cross fires a good bit.

When stuffed with a 1 1/4 oz. load running at a lower velocity, say 1125 fps, to 'tame recoil' that gun will spread fire, ie the right barrel will shoot to the right. Guaranteed.

Bore time trumps mass of ejecta. A heavier bullet will cause a pistol to shoot higher.

So, field guns that crossfire with target loads are not necessarily built wrong. Neither are trap guns that throw duck loads off to the side.

Eightbore in theory you are right. I've seen doubles that had patterns not together at any point. I had a 20 bore which sent the left bore pattern down six inches and left a foot at 21 yards when you compared it to the right barrel or the point you were aiming at. The right barrel was dead on at 21 yards. The left was not. Those patterns did not converge or stay together. They diverged. At 35 yards the left barrel was useless. Don't know if it was poor regulation or chokes being poorly cut. I sent it down the road.

We assume barrels are regulated but have no way to know this without patterning them. Gun makers use a jig to align barrels for joining and statistically it must work almost all the time. I've seen screw in choke tubes which were certainally cut off bore so much that eccentric choke tubes were required to correct where the pattern was. When in doubt go to the pattern plate.

It might still have more to do with the bore time than the heavier bullet.

Which is what I said.

Or thought I said.

One would perhaps expect a heavier bullet to shoot lower, because it's going slower.

It does not, due to 'bore time'.

You have to see where the pattern is being thrown from each barrel. Where's the POI in relation to the POA and where is the pattern in relation to those two plus how uniform is the pattern for a particular payload.

Is it low, high to the right to the left, a lot goes into patterning a shotgun.

I wish more people would pattern their shotguns and post the results for discussion.

You also have to ask yourself how close is close enough.

Correcting a 5" impact error for a guy who can't consistently point within that tolerance is, pardon the pun, pointless.

That's roughly the diameter of a clay target. Can you tell if you're pointing at the forward edge of the target or the trailing edge?

I can't.

This can be rather like a piss poor shot blaming choke selection for a pattern that's 6" too small when he just missed the friggin' target by 6 feet.

There's no excuse for the enormous lack of regulation reported by some, but I've only encountered one gun that was truly made wrong and utterly useless. It was a Rem Choke installed sideways.