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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Having problems with getting consistant velocity
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<blockquote data-quote="Darryl Cassel" data-source="post: 21434" data-attributes="member: 34"><p>Hello Tx</p><p></p><p>The problem with the bigger cases is usually there are too many varibles the bigger you go especially when they are necked down very far. Can make for a very overbore situation.</p><p></p><p>More powder, bigger cases (with room for error in manufacturing), more chamber heat, and relativly small bullets with a lower BC being driven down the barrel at extreme velocity all add up to eratic bullet behavior downrange from shot to shot. Some bullets will simply not give good accuracy at extreme speeds. If you have ever seen the back end (Boat tail)base of a bullet that has been fired, it sometimes is pushed into an uneven or distortion which will cause rapid decay of shot to shot accuracy.</p><p></p><p>Excessive speed has always been the cause of inaccuracy in rifles especially in 1000 yard match guns. We get the best accuracy when we slow them down a bit. There seems to be a certain speed that most all bullet weights will perform well at. For instance, I can and did run my 300 gr 338/416 Rigby imp to 3310 FPS. It shot extremely flat at that speed. My 100 yard groups were 1 1/2" and should have been one cloverleaf hole. After losing my cases after 2 loadings, I decided to lower the speed because the high BC of the bullet, really didn't need that much speed to perform well at extended ranges. I slowed it down to 3150 & 3200 FPS and I extended my brass life to 7 or 8 loadings and the accuracy is better (cloverleaf) and the efectivness of the 300 gr Sierra MK bullet is still there. </p><p></p><p>It seems that most shooters want to drive the bullet as fast as they can for whatever reason. I use to think this way untill I started working with higher BC bullets that were heavier. I'm an old 6.5/300 Weatherby fan (still have two of them) with long barrels and know what some calibers are capable of when pertaining to speed and accuracy.</p><p>Excessive Speed not only kills accuracy, it destroys barrels and cases MUCH faster.</p><p></p><p>I will never forget a statement from the well known Williamsport gunsmith, Howard Wolfe, who said (after we were talking about excessive speed) "I never heard a deer or elk complain as to how many extra clicks were put on to kill it."</p><p></p><p>Remember also that some bullets will group well at 100 yards and do lousy at further ranges while others will group well at 500 and 1000 yards better then closer yardages.</p><p>It's in the stabilization range of the bullet.</p><p></p><p>Maybe you can push it further but, in my experiance, it only made it worse.</p><p></p><p>Let us know your outcome as I will soon have one to work with on the 300 Ultra IMP case but, I will be using the 30 cal 240 gr Sierra which has a much higher BC then the 270s.</p><p></p><p>Good luck to you.</p><p>Darryl cassel</p></blockquote><p></p>
[QUOTE="Darryl Cassel, post: 21434, member: 34"] Hello Tx The problem with the bigger cases is usually there are too many varibles the bigger you go especially when they are necked down very far. Can make for a very overbore situation. More powder, bigger cases (with room for error in manufacturing), more chamber heat, and relativly small bullets with a lower BC being driven down the barrel at extreme velocity all add up to eratic bullet behavior downrange from shot to shot. Some bullets will simply not give good accuracy at extreme speeds. If you have ever seen the back end (Boat tail)base of a bullet that has been fired, it sometimes is pushed into an uneven or distortion which will cause rapid decay of shot to shot accuracy. Excessive speed has always been the cause of inaccuracy in rifles especially in 1000 yard match guns. We get the best accuracy when we slow them down a bit. There seems to be a certain speed that most all bullet weights will perform well at. For instance, I can and did run my 300 gr 338/416 Rigby imp to 3310 FPS. It shot extremely flat at that speed. My 100 yard groups were 1 1/2" and should have been one cloverleaf hole. After losing my cases after 2 loadings, I decided to lower the speed because the high BC of the bullet, really didn't need that much speed to perform well at extended ranges. I slowed it down to 3150 & 3200 FPS and I extended my brass life to 7 or 8 loadings and the accuracy is better (cloverleaf) and the efectivness of the 300 gr Sierra MK bullet is still there. It seems that most shooters want to drive the bullet as fast as they can for whatever reason. I use to think this way untill I started working with higher BC bullets that were heavier. I'm an old 6.5/300 Weatherby fan (still have two of them) with long barrels and know what some calibers are capable of when pertaining to speed and accuracy. Excessive Speed not only kills accuracy, it destroys barrels and cases MUCH faster. I will never forget a statement from the well known Williamsport gunsmith, Howard Wolfe, who said (after we were talking about excessive speed) "I never heard a deer or elk complain as to how many extra clicks were put on to kill it." Remember also that some bullets will group well at 100 yards and do lousy at further ranges while others will group well at 500 and 1000 yards better then closer yardages. It's in the stabilization range of the bullet. Maybe you can push it further but, in my experiance, it only made it worse. Let us know your outcome as I will soon have one to work with on the 300 Ultra IMP case but, I will be using the 30 cal 240 gr Sierra which has a much higher BC then the 270s. Good luck to you. Darryl cassel [/QUOTE]
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Having problems with getting consistant velocity
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