Clean the barrel. Then look in the barrel from the breech end. At the far end of the chamber you will see a dark ring, That is the forcing cone. If it is thin like a wedding band,the cone has not been done. The wider the band the longer the foring cone. The cone can also be highly polished, then there will not be a ring. This also indicates that the forcing cone has been worked on.
It is said that a long forcing cone will improve shot patterns and reduce felt recoil. I believe it does. HMB
I am not sure I can always tell by looking. What actually happens is that the angle of the forcing cone is changed and this increases its length. It seemed logical to me that this might improve patterns, so I had it done on all of my barrels. I could not see a measurable pattern improvement, but patterns can be difficult to measure and compare. I can say with certainty that the forcing cone work I had done did not hurt my patterns.
There is no logical way that changing the angle of the forcing cone could reduce recoil. Decreasing the resistance to the movement of the wad/shot through the barrel would increase velocity and increase recoil.
"There is no logical way that changing the angle of the forcing cone could reduce recoil. Decreasing the resistance to the movement of the wad/shot through the barrel would increase velocity and increase recoil."
Wrong answer Pat. Better get the "physics" book out.
No gun of mine with extended forcing cones shot any better than standard, so I took a very, very good 870, patterned it, sent it out for "cone work," and patterned it again with the same shells. Here's what I got. This doesn't mean it never works; just that it didn't work this time.
ebsurveyor - My Physics book explains: Decreasing resistance would increase acceleration and increased acceleration does increase recoil. Resistance to the acceleration does not have a direct relationship to recoil. Indirectly, it could reduce acceleration and reduce recoil. Decreasing the resistance would decrease chamber pressure but it has been clearly established that chamber pressure does not have a direct influence on recoil.
If we change the question to the amount of force required to achieve a given amount of acceleration, then it is possible that the angle of the forcing cone could have an effect, but that is not the question posed on this thread.
Please help me understand what is incorrect with my book.
when i set up an 870 for my 11 year son i reamed the forcing cone and lengthened the chamber. i then polished and reblued the fresh metal. the felt recoil is substansially less. the reason it reduces recoil is that the lenghthened cone reduces pressure by lessing the constriction or restiction for movement at the time when the pressure is the greatest. I believe the recoil curve is affected, in other words the absolute recoil may be the same but it has a gentler push at he beginning.
the cone i reamed has at least a 1 inch transition and the chamber is almost 4 inches long.
i load a 7/8 oz load of 7 1/2 shot and he has fun, without a great deal of recoil.
Lengthening a forcing cone (and/or overboring) can lessen actual recoil by letting gas escape around the wad and shot. The more 'blow by' the lower the velocity, there for less recoil. It is cheaper and more effective to use lower velocity shells to reduce recoil. Long forcing may reduce the number of damaged pellets and thus reduce the number of 'flyers'. Using the hardest shot available also reduces deformation/flyers. Using a shorter shot column (less pellets) has also been shown to reduce pellet deformation. Simply put... lowering velocity in lighter loads is the most effective way to reduce actual recoil. The best way to reduce felt recoil is a proper fitting gun and a mechanical recoil reducer such as RAD, Bumpbuster, PFS, etc. Merry, Merry. TJ
I invite anyone to post valid evidence that lengthening forcing cones inproves pattern efficiency. Why is it that Neil cannot see any improvement after several tests but others see it every time like it's predictable magic?
I would think that this forum would be a very good place to advertise the astounding results of barrel modifications done by the top barrel smiths around the country. Surely they have irrefutable evidence of their years of improvements. But never a word. It seems to be like religion, gotta have faith or one can't see it.
Made a reamer in the tool room years ago which lengthened both the chamber and the forcing cone. Did most of my 870 barrels with it plus a few for others. Couldn't see any difference in recoil or patterns. Didn't hurt either. I do believe that recoil is reduces a little as the shot and wad don't have to turn as sharp a corner right after leaving the shell with the long taper versus the sharp angle of the factory cone.
I've left the reamer on the shelf for years now and just shoot and have fun. Kind of tired of analysis, more fun to shoot.
Here's what I know: About 15 years ago, I had a TMX choked 40+ thousands that I had been shooting for at least four years. I had not had a 200 for several years. I had the barrel opened 10 or 15 thousandths and the forcing cone lengthened to 6" and the choke opened to 40 thousandths. Recoil dropped dramatically and I had three 200's in the next month. Velocity increased (was measured) and I assumed pressure decreased (bigger hole).
I am not trying to be a smart ass, but how many shooters out of 100 would feel less recoil if they seen a gunsmith reaming a forcing cone with no clearence on the flutes of the reamer. Then go in and polish up the so called lengthened cone? Its called the placebo effect.
Unless the barrel work does something to the rate of acceleration of the shot, there cannot be an effect on recoil. Most of the acceleration takes place well after the shot has left the area or the forcing cones.
A couple of posters have also lengthened their chambers. This surprises me. Lengthening the chamber could easily result in damage to the wad
ebsurveyor- I am trying to understand your results. You stated that shot velocity increased and recoil decreased. If this is true, I would expect all airplanes with jet engines to begin falling from the sky soon. You also assumed that pressure decreased but peak pressure is achieved well before the front of the wad touches the forcing cone so alterations in the forcing cone could never affect peak chamber pressure.