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Forcing Cones

Discussion in 'Shooting Related Threads' started by coffee, Dec 19, 2010.

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  1. coffee

    coffee Member

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    Does anyone know when lengthening the cones if a 5 inch length is too much and is there such a thing as maybe blowback. Thanks ......... COFFEE
     
  2. hmb

    hmb Well-Known Member

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    Lengthening the forcing cone reduces the deformation of the shot while it is getting from the chamber to the narrow part of the barrel. The longer you make the entryway the gentler it is to the shot. Two inches works fine and five inches works too. No blow back that I am aware of. HMB.
     
  3. grunt

    grunt TS Supporters TS Supporters

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    Id think it ,would depend on how thick your barrel is,5" is a long way into the barrel. Could make it too thin.
     
  4. DB Bill

    DB Bill Active Member

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    I've personally looked at maybe a dozen shotgun barrels that have failed to the point there was a large hole in the side (my gunsmith collects them) and after looking at the barrels I agree with him that the culprit is a poorly done job of lengthening the forcing cones ---- either not done "straight" or to much metal removed.

    I think any effect of "doing" the cones on any change in patterning is probably less than the normal shot to shot variation in a regular barrel and there are maybe 3 or 4 gunsmiths I'd trust to do the job and none of them are cheap.

    If you have a modern gun I'd leave it alone.
     
  5. phirel

    phirel TS Member

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    The length of the forcing cone is a poor way to measure the work. What is happening is that the angle of the forcing cone is altered and this results in lengthening the forcing cone.

    Pat Ireland
     
  6. Unknown1

    Unknown1 Well-Known Member

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    Leave the barrel as it is; you're not gonna see the kind of improvement you're dreaming about.

    MK
     
  7. Rastoff

    Rastoff Active Member

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    While I do believe that lengthening the forcing cone may result in reduced deformity to the pellets, I don't believe that the effect is significant enough to improve your scores.

    Will it make a difference? Sure, will it make you a AAA shooter? No!
     
  8. hmb

    hmb Well-Known Member

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    I think you would be hard pressed to find a stock forcing cone on a AAA shooters gun. HMB
     
  9. PerazziBigBore

    PerazziBigBore TS Member

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    Actually.. the Kolar.. and the new Perazzi 18.7 bores leave little room for improvment..as both have learned from our barrelsmiths what really works.. Some of the older guns could have improvments with better designed forcing cones.. designed for todays plastic wads...
     
  10. Danny B

    Danny B TS Member

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    PerazziBigBore..........I fully agree with your statement. Why??? because I own both and know there is a difference.
     
  11. Neil Winston

    Neil Winston Well-Known Member

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    This 870 barrel was pulled out of stack of similar ones because they have a reputation for short and rough forcing cones. I had several which looked just like it. In other words, this was in no way a "selected specimen" or anything similar. It's probably just like the one on your 870 in the safe, the one you put away when you got something a lot better.

    When I ran 10 Federal Papers (lot 681) through it is was clear that it was a match for - and better than, actually - any barrel on any gun I owned.

    I had the forcing cone lengthened by someone who seemed to me, as I watched him, an expert in the task. With a piloted reamer he did the job then spent a lot of time polishing it and making it look just great.

    But it made no difference.

    <a href="http://photobucket.com" target="_blank"> longshortcones-1.gif </a>

    This is why it frosts me to read as I did above, that "it will make a difference." Have any of the people who say that ever tested it? I've done it three times now and there was no difference in all three cases.

    "Your mileage may vary" but it would surprise the heck out of me if it did.

    Neil
     
  12. Neil Winston

    Neil Winston Well-Known Member

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    This mid-1970's Ithaca Perazzi - called RP for the person who campaigns it - shoots just great with its old, non-trendy bore, forcing cone, and 0.040 choke. In spite of these weaknesses it won a handicap at the Grand a few years ago.


    Compared to a lengthened-forcing cone Perazzi of a similar year and similar dimensions, it does just fine. There's no evidence that the modification did the other gun any good at all.

    <a href="http://photobucket.com" target="_blank"> Stdlongforcingcone3-1.gif </a>

    Neil
     
  13. grntitan

    grntitan Well-Known Member

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    Thanks Neil. Can't argue with facts. Now porting, that's where the real secret lies. LOL

    Matt
     
  14. PerazziBigBore

    PerazziBigBore TS Member

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    No.. I think it's a combination of things.. forcing cones alone will not change a whole bunch.. backboring alone.. will help reduce hot spots in the pattern.. as the bore gets larger.. part of that relates to how the large bore opens the forcing cone.. and how the choke section is handled in the backboring operation..

    Many of my older Perazzi barrels.. have a HOT core.. Most of my larger bore barrels.. later or worked on..have a more uniform pattern.. The percentages may be similar.. but the uniformity seem to be improved.. Now.. as I shoot only 24 gram.. I'll stay with my old.. hot core barrels.. That's what works for me.. If I shot 1 oz.. or 1 1/8oz.. the new 18.7 bore would be my cup of tea.. Now.. I do have 1 barrel 18.7mm that's factory virgin.. After I fit it to the receiver Rich Bullard sold me.. I'll report back how it patterns..if anyone wants to know.. It's .024/.032

    All Good.. Mike
     
  15. Neil Winston

    Neil Winston Well-Known Member

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    As winter sets in, MIke, I hope to draw on a lot of Perazzi patterns from all sources - factory old and new - modified and virgin - and give that "hot core" theory a good looking at.

    If the new ones do indeed have a less hot core, I expect it to be simply attributable to lower overall pattern percentages. But my mind is open and I will be interested in what I see.

    Neil
     
  16. Twinbirds

    Twinbirds TS Member

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    People look for the purchase improvement instead of hard work andeffort.
     
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