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<blockquote data-quote="chris matthews" data-source="post: 8616" data-attributes="member: 66"><p>GonHuntin,</p><p>I don't by into the "going to sleep" theory. I have built several rifles that shoot long VLD type bullets requiring fast twists into 1/4 moa groups at 100 yards. Most people say these type bullets need 200 or 300 to go to sleep and groups tighten up.</p><p>I feel it was target resolution at the longer ranges that got them smaller groups at the longer ranges.</p><p>Darryl Cassel says his big boomers shoot one hole groups at 100 also. This indicates no need for going to sleep.</p><p> I am not a ballistics expert by any means, but I don't understand how the barrel's length affects the BC. I don't remember all the factors of figuring BC, but I think the main ones are weight, time of flight, sectional density and bullet design/shape.</p><p> I have tested 308s with the same twist, 1-11, pushing 175 MK at 2650 fps out of 20, 22 and 24" barrels. Shot the same day within an hour of each other over a Oehler 35. Different glass but all of them took 34 min elevation from a 100 yard zero to get to 1000. All were supersonic and all the rifles shot 6" groups at 1000 and 1/4" at 100.</p><p></p><p>Starting velocity is the same if it's the same, I don't care what the barrel length is.</p><p></p><p>Looking at Sierra's ballistic program, they don't ask for barrel length in any of the variable conditions. And they say BC changes with velocity. Higher fps gives a higher BC. Bullets slows down, the BC goes down accordingly.</p><p></p><p>Just my thoughts on it from my experiences.</p></blockquote><p></p>
[QUOTE="chris matthews, post: 8616, member: 66"] GonHuntin, I don't by into the "going to sleep" theory. I have built several rifles that shoot long VLD type bullets requiring fast twists into 1/4 moa groups at 100 yards. Most people say these type bullets need 200 or 300 to go to sleep and groups tighten up. I feel it was target resolution at the longer ranges that got them smaller groups at the longer ranges. Darryl Cassel says his big boomers shoot one hole groups at 100 also. This indicates no need for going to sleep. I am not a ballistics expert by any means, but I don't understand how the barrel's length affects the BC. I don't remember all the factors of figuring BC, but I think the main ones are weight, time of flight, sectional density and bullet design/shape. I have tested 308s with the same twist, 1-11, pushing 175 MK at 2650 fps out of 20, 22 and 24" barrels. Shot the same day within an hour of each other over a Oehler 35. Different glass but all of them took 34 min elevation from a 100 yard zero to get to 1000. All were supersonic and all the rifles shot 6" groups at 1000 and 1/4" at 100. Starting velocity is the same if it's the same, I don't care what the barrel length is. Looking at Sierra's ballistic program, they don't ask for barrel length in any of the variable conditions. And they say BC changes with velocity. Higher fps gives a higher BC. Bullets slows down, the BC goes down accordingly. Just my thoughts on it from my experiences. [/QUOTE]
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