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.240 Weatherby Magnum: The Hotrod 6mm
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<blockquote data-quote="bounty hunter 2" data-source="post: 1100242" data-attributes="member: 90711"><p>I think your 240 will beat out your Swift by a fair margin shooting 55gn bullets even with the 24" barrel. Two reasons for that are 1 the 240 has substantially greater case volume so it will use larger powder charges. #2 When you shoot light for caliber bullets you will use powders that are faster in burn rate than you will use with bullets that are on the heavier end of the bullet weight selection for any caliber. Because of the increased powder burn rate with very light bullets the percentage of velocity loss per inch of barrel goes down. Just the opposite happens when you go to bullets weights on the heavier end. That is when the barrel length has greater effect because the much slower burning powders used with the heavier bullets in conjunction with the longer barrel have more time to push on the bullet getting it to higher velocity. Same peak pressures as with the faster powders with lighter bullets just more time to push on the bullet.</p><p>Simply put if you will only be shooting 55gn bullets in your 240 with 24" barrel you will realize little to no loss in velocity over that of a 26" barrel.</p><p>Not knowing the twist of your Swift going to a 28" barrel with it will pretty much have the same effect. I guess I should clarify heavy and light for caliber. In 243 bullet weights will range from 55gn to 110gn and in 224 cal from 35gn to 90gn.</p><p>If your Swift is a 1/14" twist the heavy end will end at about 60gn with just a couple exceptions like the 63gn Sierra and the 70gn Speer but for the most part with bullets intended for varmints and not deer the limit will be 60gn. </p><p>I have two rifles chambered for the 22/250 Ackley which in case volume are about equal to the 220 Swift. One of my rifles has a 1/14" twist and the other a 1/9" twist. The 1/14" is 28" long and the 1/9 is 27" long. The 1/14" easily gets 4000 fps with a 50gn bullet. The 1/9" I made very specifically to shoot a 70gn BTSP that I swage at home. This rifle gets 3450 fps from the 70gn bullets or I should say gets that velocity with its best grouping. It will shoot a little faster but not shoot as good. The maximum point blank range between these two loads is not that vastly different as you might think. The real gain is not so much in trajectory as it is in wind drift. Adding that 20gn weight to an efficient shape has great effect in forgiving my inability to accurately judge the wind.</p><p>Another point I would like to bring up is bullet construction and its effect on achievable velocity with good accuracy. I mentioned that I swage a 70gn .224" BTSP bullet. I make these using 22LR spent cases for jackets. Compared to commercial jackets the 22 RF jackets are very thin and soft. I was shooting these in a 223 chambered rifle with 1/9" twist for harvesting coyotes and they work very well indeed rarely ever exiting a coyote. In the 223 chamber my top velocity with this bullet weight was 2900 fps and best accuracy was closer to 2800 fps.</p><p>I felt that with a larger chambering the resulting higher velocity would give me greater range potential with this bullet so I built the 22/250 Ackley mentioned earlier with 1/9" twist 27" barrel. What I discovered was that even though these bullets shot well from the 9" twist 223 at 2900 fps the larger volume of the 22/250 Ackley could only gain about 100 fps and hold the same accuracy level. Over that velocity and the torque is too much for the thin jacket bullets to handle. Go to the full velocity potential of the cartridge with the thin skin bullets and they spray a shot gun pattern at 100 yards.</p><p>I was able to cure the shot gun pattern by making these bullets with Sierra J-4 jackets which are much heavier by about 5gn and have a progressive taper from base to nose where the 22 RF jackets are uniform in thickness for their length.</p><p>Lesson learned here is that bullet design will be a factor in the end result of how good a load will shoot at what velocity regardless of the chambering of the rifle its being launched from.</p><p>Well I have rambled enough and besides my wife may soon catch me here burning my work day and getting nothing else done.</p></blockquote><p></p>
[QUOTE="bounty hunter 2, post: 1100242, member: 90711"] I think your 240 will beat out your Swift by a fair margin shooting 55gn bullets even with the 24" barrel. Two reasons for that are 1 the 240 has substantially greater case volume so it will use larger powder charges. #2 When you shoot light for caliber bullets you will use powders that are faster in burn rate than you will use with bullets that are on the heavier end of the bullet weight selection for any caliber. Because of the increased powder burn rate with very light bullets the percentage of velocity loss per inch of barrel goes down. Just the opposite happens when you go to bullets weights on the heavier end. That is when the barrel length has greater effect because the much slower burning powders used with the heavier bullets in conjunction with the longer barrel have more time to push on the bullet getting it to higher velocity. Same peak pressures as with the faster powders with lighter bullets just more time to push on the bullet. Simply put if you will only be shooting 55gn bullets in your 240 with 24" barrel you will realize little to no loss in velocity over that of a 26" barrel. Not knowing the twist of your Swift going to a 28" barrel with it will pretty much have the same effect. I guess I should clarify heavy and light for caliber. In 243 bullet weights will range from 55gn to 110gn and in 224 cal from 35gn to 90gn. If your Swift is a 1/14" twist the heavy end will end at about 60gn with just a couple exceptions like the 63gn Sierra and the 70gn Speer but for the most part with bullets intended for varmints and not deer the limit will be 60gn. I have two rifles chambered for the 22/250 Ackley which in case volume are about equal to the 220 Swift. One of my rifles has a 1/14" twist and the other a 1/9" twist. The 1/14" is 28" long and the 1/9 is 27" long. The 1/14" easily gets 4000 fps with a 50gn bullet. The 1/9" I made very specifically to shoot a 70gn BTSP that I swage at home. This rifle gets 3450 fps from the 70gn bullets or I should say gets that velocity with its best grouping. It will shoot a little faster but not shoot as good. The maximum point blank range between these two loads is not that vastly different as you might think. The real gain is not so much in trajectory as it is in wind drift. Adding that 20gn weight to an efficient shape has great effect in forgiving my inability to accurately judge the wind. Another point I would like to bring up is bullet construction and its effect on achievable velocity with good accuracy. I mentioned that I swage a 70gn .224" BTSP bullet. I make these using 22LR spent cases for jackets. Compared to commercial jackets the 22 RF jackets are very thin and soft. I was shooting these in a 223 chambered rifle with 1/9" twist for harvesting coyotes and they work very well indeed rarely ever exiting a coyote. In the 223 chamber my top velocity with this bullet weight was 2900 fps and best accuracy was closer to 2800 fps. I felt that with a larger chambering the resulting higher velocity would give me greater range potential with this bullet so I built the 22/250 Ackley mentioned earlier with 1/9" twist 27" barrel. What I discovered was that even though these bullets shot well from the 9" twist 223 at 2900 fps the larger volume of the 22/250 Ackley could only gain about 100 fps and hold the same accuracy level. Over that velocity and the torque is too much for the thin jacket bullets to handle. Go to the full velocity potential of the cartridge with the thin skin bullets and they spray a shot gun pattern at 100 yards. I was able to cure the shot gun pattern by making these bullets with Sierra J-4 jackets which are much heavier by about 5gn and have a progressive taper from base to nose where the 22 RF jackets are uniform in thickness for their length. Lesson learned here is that bullet design will be a factor in the end result of how good a load will shoot at what velocity regardless of the chambering of the rifle its being launched from. Well I have rambled enough and besides my wife may soon catch me here burning my work day and getting nothing else done. [/QUOTE]
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.240 Weatherby Magnum: The Hotrod 6mm
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