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lengthing forcing cones

Discussion in 'Shooting Related Threads' started by dutchman1968, Apr 22, 2010.

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  1. dutchman1968

    dutchman1968 Active Member

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    Ladies and Gentleman, I know this subject probably has been beaten to death along with barrel porting but, as of right now my barrels are unmolested. But I was thinking on lengthening the forcing cones. The question is, what company to have do it and how long 2-3 inches or 4-5 inches? Any input would be greatly appreciated. Thanks Troy
     
  2. Dr A C Jones

    Dr A C Jones Member

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    My advice: Pattern test the gun thoroughly, tell the prospective barrel man what you have done and send him the test results. Go with the one who agrees to a no measurable improvement, no fee arrangement.


    Andrew.
     
  3. g7777777

    g7777777 TS Supporters TS Supporters

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    Who would agree to that? and if they did it would cost a fortune

    Either you want the forcing cones lengthened or you dont

    regards from Iowa

    Gene
     
  4. Dr A C Jones

    Dr A C Jones Member

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    Somebody able to make a measurable improvement?


    Regards from Missouri.


    Andrew.
     
  5. Neil Winston

    Neil Winston Well-Known Member

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    Gene, it wouldn't cost anything.

    Neil
     
  6. Unknown1

    Unknown1 Well-Known Member

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    There's no logic in taking the chance of screwing up a good barrel chasing an "improvement" you probably don't need and will most likely never notice. Leave the thin alone!

    MK
     
  7. Tron

    Tron Supporting Vendor Supporting Vendor

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    I believe it does improve patterns at longer distances and I will prove it in the near future. I have a 28" 303 Sporting barrel with factory Mobile chokes. I will lengthen the forcing cones AND have it back bored and post before and after results. I'd say withing a few weeks or so.
     
  8. jdsfarms

    jdsfarms Well-Known Member

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    Tron,Do you think it makes a difference in recoil,I have shot an 885 SKB and a 85tss the 85tss definately has less recoil and the only difference I see is it has the forcing cones lengthened and the 885 does not,both are backbored.Jerry
     
  9. Tron

    Tron Supporting Vendor Supporting Vendor

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    I believe that it can reduce FELT recoil to some degree, because I've had identical guns with and without back boring/forcing cones and there was a deffinate difference. I really noticed that I could take much further shots in Sporting Clays with worked barrels. There is no doubt about that what so ever in my mind.
     
  10. Neil Winston

    Neil Winston Well-Known Member

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    Tron, my bet - a cup of coffee - is that your result will be no different from mine.

    <A NAME="84782">Subject:</A> When you lengthen a forcing cone (Winston)<BR>
    From: Neil Winston<BR>
    Email: <BR>
    Date: 12-Jan-08<BR>

    I've compared the patterns of similar guns, one with a lengthened forcing cone, one stock and never seen a difference. The link above give an example.

    But comparing two guns isn't the ideal experimental design. To be fair, one should test a gun, have the forcing cone lengthened, then retest the gun.

    The gun pictured below is an 870, at least 30 years old. It was tested twice - a year apart - with the same lot number of 3-dram 7 1/2 Federal Papers, in low-80 degree weather at Metro Gun Club in Blaine, Minnesota. The distance was 40 yards.

    Here are the results. Each pair of lines represents the pattern percentage in one of three areas: The zero-to 20-inch circle, the 20 to 30-inch ring, and the whole 30-inch circle.

    longshortcones2.gif

    Though none of the differences are statistically significant, one things clear. Lengthening the forcing cone didn't do this gun any good.

    Neil
     
  11. Dr A C Jones

    Dr A C Jones Member

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    Neil, Are you sure the 30-inch PEs are not statistically signifcantly different? I just took the numbers roughly by eye as PE_before = 80% +/-2% and PE_after = 82% +/-2% which is pretty close to statistically significant.


    I know, not practically significant but the graph looks like a difference.

    Anyways, not in favour of cone work.


    Andrew.
     
  12. short shucker

    short shucker TS Member

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    I have no way of proving it, but I believe that lengthening the forcing cones in certian barrels does have merit.

    I've really found an improvement in my mobile choked barrels. The felt recoil was changed a bit, took a little initial bite out of it and created more of a shove. The down range ballistics seem to be improved as well.

    I will look forward to Tron's results when posted.

    ss
     
  13. dutchman1968

    dutchman1968 Active Member

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    even if it doesn't give a better pattern, I feel that there is less felt recoil with longer cones, its more of a shove than a quick hit. I have had brownings with ported overbored barrels that kicked and had a Rizzini with tight nonported barrels that had factory 5" lengthened forcing cones and the kick seemed tamer. I know a guns fit come into play as well. Troy
     
  14. Neil Winston

    Neil Winston Well-Known Member

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    46, I tried the lengthened-cone barrel and switched to a standard one to see if I could tell a difference. I thought that maybe the long-cone barrel was a little softer; the other tester thought the opposite. Again, conservatively, I concluded that there was no difference. What has never been explained to me is why a long cone should kick less. Or more, for that matter, since there was no difference in the chronographed speed of the shot from the two barrels.

    Neil
     
  15. Unknown1

    Unknown1 Well-Known Member

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    Felt recoil is a matter of physics: the force resulting from a mass accelerating. If neither one is changed, the felt recoil remains the same.

    Anyone who tells you something ridiculous like "the longer cone spreads the felt recoil out over a longer time" is trying to convince the gullible that they can feel changes in actions that occur in thousandths of a second. Can't be done by a human.

    MK
     
  16. dverna

    dverna Active Member

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    Perception is "reality". If you think it improves recoil and/or patterns - you might be happy.

    Andrews made a good point. But we all know if we shoot enough patterns one will look better than another - so "proof" may be difficult to determine unless we measure the average of 5-10 consecutive shots.

    I shoot with a guy that has barrel work from a well known barrel-smith. I shoot a stock K-80. After one of our typical smoke-fests he looks at me, smiles, and asks, "When are you sending those barrels out to ____________?" He is convinced that I would be wasting money to have my gun touched. The way the gun crushes birds I would be a fool to change anything.

    If you have a gun that shoots like crap, and a barrel guru can get it right, it is money well spent. Just follow Andrews advice - or at least pattern it first - as I doubt anyone will agree to a money back guarantee.

    Don Verna
     
  17. Neil Winston

    Neil Winston Well-Known Member

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    Andrew, I get a t probability of 0.1884 and I use P=0.05 to make my judgement of significant.

    Neil
     
  18. halfmile

    halfmile Well-Known Member

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    This cabbage has been chewed before, as noted.

    The fact is it's not a matter of length, rather of degree of taper.

    My forcing cone reamer is ground at 1 & 1/2 degrees. It will make a shorter cone in an overbored barrel. In a .726 Beretta barrel it makes a longer cone.

    The reason for doing the job is to insure that there are fewer pellets deformed by the pressure on them if they are restricted by the cone.

    Many tests have been done by many people, and all I have read says the 1 & 1/2 degree taper works best, both for forcing cones, and for the leade into the choke.

    HM
     
  19. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    Do we know the original purpose of forcing cones in shotguns and why the standard was set in stone from the beginning of breech loading shotguns? One more, are they necessary today with the advent of the all plastic wads?

    I feel it's possible that shooters feel the initial forward pull on a shotgun due to tighter friction with forcing cones and modern day wads. An ever so slight forward movement may be the cause of more "felt" recoil with the forcing cones than those without. Those without a cone would have less forward pull along with less internal barrel friction. It's entirely possible that is the difference some can feel while others can't.

    Hap
     
  20. Dr A C Jones

    Dr A C Jones Member

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    Thanks Neil. "by eye" it looked like a real difference but I just put the numbers into Excel (read by eye from your graph) and put the mean and SDs into the above applet (I can't remember the algorithm I used) and it gave 79.5% confidence level of a genuine difference.


    Both v.tight guns though!


    Andrew.
     
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