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Longer barrel=more velocity-how much for shotguns?

Discussion in 'Shooting Related Threads' started by mtimney, Oct 22, 2012.

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  1. mtimney

    mtimney TS Member

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    Anyone ever measure the velocity difference between different length trap barrels? What does two more inches get you in speed?

    This question came out of a discussion I was having about the possible advantages of a single barrel over a double for trap. While I don't know if any of the other claimed advantages of a single over a typical double are true, there was a thought that maybe a single barrel would absolutely be superior in velocity.... as most are at least 2 inches longer than typical double.

    Mark T.
     
  2. BT-100dc

    BT-100dc Active Member

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    I have read that the gain is 10 fps per inch; i.e., if a 30 inch barrel muzzle velocity is 1,145 fps then a 34 inch would be approx. 1,185 fps. I understand you will also pickup some extra velocity with an overbored gun as compared to the traditional .725 bore size. If I'm wrong, thread me. BT100dc
     
  3. timb99

    timb99 Well-Known Member

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    Its probably not within the measuring accuracy of the chronograph you would be using.
     
  4. hmb

    hmb Well-Known Member

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    Added barrel length can cause a reduction in velocity due to friction. It all depends on when the powder completes its burn. HMB
     
  5. wireguy

    wireguy TS Member

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    Slow burning powders continue burning and building pressure and speed in longer - up to a point - barrels. Fast burning "target" type powders burn so quickly they are finished in something like the first 18" and are on inertia after that.
     
  6. Perazzi_MX8

    Perazzi_MX8 Well-Known Member

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    I have a chronograph and experiment a lot. I have shot 10 Winchester "AA" Super-Handicaps from a Browning BT-99 34" and 10 from a Citori 30" from the same box. The average was 1303 fps. from the 34" barrel and 1265 fps. from the 30" barrel. All of the barrels are over-bored and ported. Factory test barrels meet SAAMI specifications, are 30" long (for 12 gauge), and are used to establish factory velocities. I have no doubt that over-bored barrels, and length, both increase velocity. One would have to use a long barrel and cut off an inch at a time to prove it exactly, but I believe it would show the same thing I have measured. All other factory shells have shown to be slightly faster than advertised in these same 2 shotguns. I have only shot some of these tests with my 32" Perazzi and it comes in very close to the midway point. It also is over-bored and ported.


    Duane Nicholson
     
  7. ovaljack

    ovaljack Member

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    it is important to keep in mind as the barrel length changes the distance from muzzle to photo cell must stay the same. in other words, you must move forward or backwards the same amount the barrel changes. I have found the change of muzzle to photo cell shows a larger change than barrel length. just try to cover all the variables. Jack
     
  8. little gambler

    little gambler Active Member

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    I had a two barrel seitz set, one 34" and one 35" same bores same chokes and difference of about 90 fps. That was shot over a competion electronics crono......l.g.
     
  9. Dr.Longshot

    Dr.Longshot Banned Banned

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    It comes close to this: a 34"inch bbl shooting 2 3/4 dram loads the speed is almost 1200fps from 1145 fps in a 30 inch Bbl. 30 inch Bbl 1145 fps 34 Inch Bbl 1200 fps.

    Gary Bryant
    Dr.longshot
     
  10. crusha

    crusha TS Member

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    It's not enough difference to bother worrying about. Shotgun powders are relatively fast-burning. Shotguns have the longest barrels of any type of small arm. With the barrel lengths you are talking about, you are very close to the point where extra length gets you no velocity advantage at all.


    In Bob Brister's Shotgunning book, he mentions he cut back a barrel from 28 to 22 inches and chronographed some magnum 20 gauge loads at both lengths, and the net effect was less than 50 fps. With faster powder and longer barrels, it would be even less.


    Shotgun barrels are long to give you a longer, more accurate sighting plane...not to get more speed.
     
  11. cubancigar2000

    cubancigar2000 Well-Known Member

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    buzz gun has it right
     
  12. halfmile

    halfmile Well-Known Member

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    50 FPS makes a difference of about 3 inches with a 30 inch pattern, at 34 yards.

    It's not enough to make you miss. The little guy inside makes that happen.

    HM
     
  13. Unknown1

    Unknown1 Well-Known Member

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    Don't know the exact correlation to target loads and 34" barrels but the chart at the bottom of this page, <I>http://www.guncustomizing.com/tech.htm</I>, deals with several sizes of hunting loads and about a half dozen barrel lengths.

    Keller
     
  14. Bluerock1

    Bluerock1 Member

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    It is about 15fps per inch.

    BR1
     
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