I didn’t know were else to turn to get an honest answer. I am specking out a new Spanish double and I was told that ordering a 3″ chamber in a 12 gauge will effectively reduce felt recoil as it acts like a longer forcing cone. I read your section in the shotgun report and you didn’t mention chamber length as a factor.
OK to the meat of my question: say I had two equal 12 gauge shotguns weighing 6#12oz (same bore size, length of forcing cone, shooting same loads, ect..) gun #1 had 2-3/4″ chamber and #2 had 3″. Will gun #2 with 3″ chambers “shoot softer”?
Thanks as always for your help.
I don’t know if I can supply an “honest” answer, but I’ll tell you what I think. Warning: I sometimes have dishonest thoughts.
Personally, I have never been able to prove that longer forcing cones reduce recoil in every application. I’ve had two identical gun, one with long cones, one with standard 1/2″ cones. Both kicked about the same. Other people swear that lengthening the cones on their gun changed it. So often when cones are lengthened, other work is performed so it’s hard to tell what does what.
One of the disadvantages of long cones that no one talks about is that you can get gas blow-by if your wad fails to properly obturate in cold weather, due to inferior plastic or due to a fiber wad. The longer the cone, the worse the problem. I’ve seen it happen with “promo” loads in a gun with 5″ custom cones. Nothing is for free. If long cones were all that perfect in every way, all the manufacturers would use them. They don’t cost any more to cut in at the factory. Why doesn’t anyone ever ask that question? Most manufacturers don’t use very long cones for a reason. They don’t work well with all types of ammo in all conditions.
Do 3″ chambers act like long cones? Dunno. The whole point of long forcing cones is to provide a smooth transition from chamber to bore. 3″ chambers don’t exactly do that. Most standard 12 gauge bores have 5 degree forcing cones of around .4″ in length. Obviously, many manufacturers alter this. Brownng keeps short cones, Beretta usually has medium length ones and Krieghoff comes with longer ones. Still, the forcing cone in a 3″ chamber isn’t any different than it is in a 2-3/4″ chamber other than the fact that the loads gets an extra 1/4″ to “run” before it hits the cone. That extra 1/4″ is at the full .800″ chamber diameter. Modern plastic wads “usually” obturate properly even in an .800″ bore (see Stan Baker’s .800 bore Big Bore barrels), but nothing is guaranteed. With the wrong shell under the wrong conditions, 3″ chambers could cause blow by.
Does it concern me? Nope. I am currently awaiting delivery of a Poli shotgun from Italy that I have had made. Though it is a SxS field gun and I won’t use magnums, I did specify 3″ chambers. I did this because the test Poli Ivory Deluxe pigeon gun I shot for a my gun review column in The Clay Pigeon also had 3″ chambers and a .731″ bore. It was the softest shooting SxS I have ever used, so that’s the bore measurements I ordered on my gun.
Many, many manufacturers chamber just about all their 12s in 3″ and don’t report any problems. I figure that they wouldn’t do it if modern shells experienced blow-by.
One thing that you should consider though. Usually, when a SxS is made with a 3″ chamber, the maker assumes that you will be using 3″ shells in it. Thus the gun will be proofed for 3″ magnums and must often be built heavier. This is particularly true of Spanish and English guns. Some of these makers won’t make you a light 3″ gun. When you are dealing with light field guns, the barrels are built to the shell. 3″ is heavier than 2-3/4″ than 2-1/2″ than 2″. A properly designed gun is designed around the shell it will shoot. Mass produced guns are so overbuilt, it really doesn’t matter, but the custom stuff is another story. Check with your makers about what a 3″ chambered gun will weigh.
The Technoid writing for Shotgun Report, LLC