My only data is from shooting my two 7mm Weatherby Magnum rifles with 24” and 26” barrels respectively. There is about 20 fps difference between them with the same load of Norma MRP and 150 gr TTSX bullets. One is a hammer forged Howa barrel and the other is a button rifled Krieger Criterion barrel. Obviously two very different barrels but actual velocity differences can really be shown by cutting off a barrel inch by inch and measuring the same load speeds. I think this method has generally shown 20-25 fps per inch. I would think that different powders with different pressure curves might be a factor also. MD has several articles on this subject. Happy Trails
Life Member NRA, RMEF, American Legion, MAGA. Not necessarily in that order.
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