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FORCING CONE ?

Discussion in 'Uncategorized Threads' started by BAD 303, May 26, 2007.

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  1. BAD 303

    BAD 303 Active Member

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    Has anyone seen a study done on forcing cone length or shape for best results?I am curious why a short cone seems to pattern better and recoil less to me.Ken Eyster did a barrel for me and it has less recoil on the same gun and it is the same bore diameter.He liked short cones and i am wondering why.
     
  2. Neil Winston

    Neil Winston Well-Known Member

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    B'3, if it has the same same bore diameter and same forcing cone, how do you account for it kicking less. In answer to your question, I don't think anyone has published anything serious about forcing cones.

    Neil
     
  3. JLW

    JLW TS Member

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    I think there was a study done some time back by a ballistician in Ohio or Indiana and the work was published in Double Gun Journal.

    I can't understand less recoil on a shorter cone as the current thought is to lengthen short cones, spreading the constriction to bore over a greater distance and duration, reducing perceived recoil.-Jerald
     
  4. 1Gold

    1Gold TS Member

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    BAD,

    Actually, Ralph Walker, in his book, "The Gun Digest Book of Shotgun Gunsmithing" (Library of Congress catalog card #83-70144), wrote extensively about his personal work and testing on forcing cones. He devoted an entire chapter(#10)on his results. It is excellent work, and chronicles his test results from factory specs to overbored to going too long.

    Larry Nialon, in his book, "Shotgun Recoil - an electronic analysis" goes so far as to discuss the relationship of forcing cone length and burn-rates of powders.

    Chris Christian, in his book, "Trap & Skeet Shooting" (Gun Digest) goes into the effects of lengthening forcing cones in chapter 26, "Hotrodding Your Shotgun".

    Bob Brister's book, "Shotgunning - The Art and the Science" has chapter 11, on barrels, chokes and forcing cones. Though not as empirical, Brister is certainly respected.

    I'd be interested in your description of Eyster's work. Just how short, is "short", and what is the bore diameter?

    JBear
     
  5. phirel

    phirel TS Member

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    Lengthening the forcing cone intuitively seems like it would reduce shot deformation. Also, by reducing the initial resistance to the travel of the shot mass, felt recoil, not total recoil, would be eliminated.

    But, the lengthening of the forcing cone is very small and the effect on recoil is so very slight, if any, nobody could tell any difference. I did pattern my single barrel before and after lengthening the forcing cone. I could not tell any difference between the before and after patterns. My conclusion was that lengthening the forcing cone did not do any damage to my barrel.

    Pat Ireland
     
  6. Harold

    Harold TS Member

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    Pat wrote: "Also, by reducing the initial resistance to the travel of the shot mass, felt recoil, not total recoil, would be eliminated."

    How does reducing the resistance to travel reduce the felt recoil?
    If the resistance to travel is high enough, there will be no travel at all, and no recoil.
     
  7. Bob Schultz

    Bob Schultz Well-Known Member Supporting Vendor

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    Lenthening a forcing cone on a gun having normal to modest recoil and throwing good patterns is genrally a waste of money. On the other hand I have owned and sold many guns where there were some issues with the patterns and recoil was excessive where a forcing cone job really helped. Like most things, one needs to diagnose problems on an individual basis. (Don't fix what ain't broke.)

    The only caveat I can offer is IF you have barrel work done give it to someone who knows what they are doing! (i.e.: Wilkinson, Allor, Eyster, Briley etc.)

    Break em' all!

    Bob Schultz
     
  8. Bob Schultz

    Bob Schultz Well-Known Member Supporting Vendor

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    Lenthening a forcing cone on a gun having normal to modest recoil and throwing good patterns is genrally a waste of money. On the other hand I have owned and sold many guns where there were some issues with the patterns and recoil was excessive where a forcing cone job really helped. Like most things, one needs to diagnose problems on an individual basis. (Don't fix what ain't broke.)

    The only caveat I can offer is IF you have barrel work done give it to someone who knows what they are doing! (i.e.: Wilkinson, Allor, Eyster, Briley etc.)

    Break em' all!

    Bob Schultz
     
  9. BAD 303

    BAD 303 Active Member

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    I should have stated the two barrels are both .725 bore Beretta 303 barrels and one has long cones from Lazer-Port and the other is the barrel that Ken did the cones on.The one Ken worked on has about 3" cones and the other is about 5".There is a difference in recoil and in the patterns.I just am trying to figure out why.The chokes are switched from one to the other but does not pattern as well in the Lazer-port barrel.
     
  10. Lkn4rocks

    Lkn4rocks TS Member

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    When considering lengthening the forcing cone, the prime reason should only be for shrinking the size of the pattern due to deformed shot, and nothing to do with felt recoil....Recoil is a derivate of gun weight, velocity of the projectile and weight of that projectile....Lengthening the forcing cone only enlarges the chamber, decreasing both chamber pressure and velocity of the projectile.

    Prior to any forcing cone work, chronograph a know load ( exact grains for both shot and powder ), find the average over 10 rounds....After the forcing cone work, find the average again just a before and you will notice a drop in both velocity and felt recoil....Now increase the powder charge of the same known load until you reach the same velocity of that prior to lengthening the forcing cone, notice the felt recoil is the same as before the work.
     
  11. halfmile

    halfmile Well-Known Member

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    I don't have the recollection of the published work, but definitely remember a study of forcing cone effects on patterns, and it was determined that 1 & 1/2 degrees was as mach as needed, and any shallower angle wdorked no better.

    By the way., using a definition of length regarding forcing cones has no bearring in fact. bore size will determine length. The same reamer will produce 2 different length cones in 2 different bore sizes.

    But people still cling to that particular fallacey, as well as the "more is better" hoax.

    HM
     
  12. zzt

    zzt Well-Known Member

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    Bad 303, Ken Eyster told me he likes forcing cones about the length of Kreighoff cones. That's about 3". The magic is in the profile, the radius he puts on the cone/barrel intersection, and the finish.
     
  13. phirel

    phirel TS Member

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    Harold- You read my post more carefully than I wrote it. When I typed the word "reduced" it came out as "eliminated". And, after considering that sentence, I now believe it should be eliminated.

    Total recoil will depend on how much mass is moving forward. Felt recoil will depend on the rate at which the mass moves forward (this of course ignores the counter actions of my PFS). I cannot visualize how changing the forcing cones will significantly alter the movement of the mass through the barrel.

    Thanks for pointing out my error. Sometimes what I intend to say is not what comes out of my mouth and fingers.

    Pat Ireland
     
  14. hmb

    hmb Well-Known Member

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    Lengthening the forcing cone requires removing metal from the barrel. This reduces the weight of the gun. Thus recoil is increased. HMB
     
  15. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    "The only caveat I can offer is IF you have barrel work done give it to someone who knows what they are doing! (i.e.: Wilkinson, Allor, Eyster, Briley etc.)"

    Break em' all!

    Bob Schultz

    Very good advice Bob!

    As strange as it sounds and for whatever reason, a botched cone job can also have a drastic ill effect on how your gun patterns! I don't know why but know mine was butchered and shot terrible till I got it straightened out. (And, polished properly!) Something most fly by nighters don't do. Hap
     
  16. Harold

    Harold TS Member

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    Mike wrote: "My best guess is the longer cones..highly polished extend the timing of restriction which would corelate to recoil over a LONGER moment.."

    How does the timing of restriction correlate to recoil over a longer moment?
     
  17. phirel

    phirel TS Member

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    Keep in mind that the few lengthened forcing cones I have measured appear to only be lengthened around 0.05 inches.

    Harold- I do not have a calculator at hand and you can do arithmetic in your head. At 1200 ft/sec, how long would it take the shot to pass through the 0.05 inches that were added to my forcing cones by lengthening them?

    Pat Ireland
     
  18. JimE

    JimE Member

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    As stated above, forcing cones are correctly measured in angles rather than a linear measurement. The old SAAMI spec was 5 ¼ degrees (if I remember correctly), but now days there are many angles that people use. The older angle was required for the older fiber wads, but as stated previously, the newer plastic wads perform better with a more acute angle. On a modern competition barrel, conditions in the forcing cone are critical maintaining an efficient pattern with a heavy center density that performs over distance. Our process starts with a two-degree angle. We then use a 1-½ degree angle to transition between the two-degree and the bore. As you can imagine, that there is now a compound angle in the forcing cone. We then smooth and polish the transition with a series of emery papers. When we are finished with the forcing cone, you have a cone that transitions into the bore along a radius. There is no longer a ‘step’ at the front of the cone where the cone ends and the bore begins. If you look in the bore, you see the distinct ring in front of the chamber, where the cone begins, then a gentle, gradual fade into the bore. In a very worse case scenario, I have seen a barrel improve efficiency by 10% by simply correcting the forcing cone. (This was an extreme example, and one will rarely see that type of improvement as a rule)

    As far as recoil is concerned, one cannot state that barrel work reduces recoil. However, many shooters state that the recoil is less after performing certain barrel functions. One can only speculate that by changing certain conditions in the barrel, that the shooter feels the recoil differently (possibly changing the timing as speculated in another post), perceiving it as ‘less’ recoil.

    Jim Eyster
     
  19. Harold

    Harold TS Member

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    Pat wrote "Harold- I do not have a calculator at hand and you can do arithmetic in your head. At 1200 ft/sec, how long would it take the shot to pass through the 0.05 inches that were added to my forcing cones by lengthening them?"

    That would be hard to do considering that the shot charge has not yet reached 1200 fps as it passes through the forcing cone, so you would need the rate of acceleration.

    My point though is that any speeding up of the acceleration in the forcing cone should result in early recoil, not delayed recoil. If somebody perceives this as less, then I guess they would perceive red dot as giving less recoil than green dot.
     
  20. JerryP

    JerryP Active Member

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    Jim, If 10% is the extreme what whould the norm be?
     
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