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Barrel Length vs FPS

Discussion in 'Shooting Related Threads' started by gjmen, Oct 22, 2009.

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  1. gjmen

    gjmen Member

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    How much does barrel length affect shot velocity (fps)? Is there a rule of thumb when it comes to barrel length? i.e. 25 fps for every 2" over 30" of barrel length? When I read the fps on a package of shells, at what barrel length is that measured at? Reloading manuals, are the recipes all tested at a certain barrel length? Thanks, gjmen
     
  2. Neil Winston

    Neil Winston Well-Known Member

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    Standardized speeds are measured with 30-inch full choke barrels, but the chronograph is special, so you probably won't get the same. Different barrels, apparently identical, will produce different speeds, but a 34-inch 870 barrel I tested was about 15 to 20 fps faster then most of the 30-inch barrels I compared it with.I wouldn't count on duplicating it, though.

    Neil
     
  3. phirel

    phirel TS Member

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    This question can require a lot of testing to get a good answer, and then that answer would only apply to the specific load tested and the specific barrels used in the test. When measuring the velocity of 10 shots, there will probably me more variation in the speed of the 10 tested shots from one barrel than there is in the average difference between the 10 shots measured using the two different barrels. Next some statistical tests must be used. A T-test will show if the two average are the same or different. I also suspect the results would only be valid at the temperature at which the tests were conducted.

    Pat Ireland
     
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