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Long Range Hunting & Shooting
newbie needs some help...again
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<blockquote data-quote="liltank" data-source="post: 391137" data-attributes="member: 13275"><p>Could be velocities, or barrel temp. Some rifles, especially factory barrels will have a tendency to climb with a heated barrel. Quick science lesson, when metal heats up, it expands. This is one of the most common causes of stringing. At longer distance it is more apparent. The reason velocity may be the issue, is that some of your loads may be shooting 20 to 100 fps faster from shot to shot. Obviously the slower shots will tend to shoot low, and the faster rounds climb. </p><p></p><p>Not sure of your OAL, but try seating them deeper. I have posted on here before about groupings at longer distance. Talking with guys that shoot competitively suggest seating bullets pretty deep for LRH and target. By this I mean seating .080" to .100" away from the lands. Both my cousin and I did this with VLD type bullets and our groups went from 1MOA to just under .5MOA and better if we do our part. This tightened up our velocities, and fliers went away. He has a 338 Lapua shooting 300SMK's. Believe it or not, his load is 50BMG 93.0grn, with a velocity of 2740 with only about a 5fps spread. I think his long barrel really helps in the consistency of burn out of this slow burning powder. </p><p></p><p>If your current load is shooting well, seating them deeper may hone in your accuracy and tighten up your velocity spread. To eliminate the heat factor, take your time in between shots. I know its tedious, but allow about 3 to 5 minutes between shots after your first 2 shots so that your barrel can stay at a consistent temperature. I have my own speculation, but the hotter the barrel, you can increase case pressure by allowing a casing set to long in a hot chamber. This also increases velocity and causes stringing. Shoot some across a chrony and see what its doing. If you have a large velocity spread, then it you may need to go to a R22, R25, H1000, Retumbo, or Hodgdon or IMR 4831. With the 250's, I would stay with R25, H1000, or the 4831's. Maximum efficiency in a cartridge is between 95% to 100% capacity. </p><p></p><p>Tank</p></blockquote><p></p>
[QUOTE="liltank, post: 391137, member: 13275"] Could be velocities, or barrel temp. Some rifles, especially factory barrels will have a tendency to climb with a heated barrel. Quick science lesson, when metal heats up, it expands. This is one of the most common causes of stringing. At longer distance it is more apparent. The reason velocity may be the issue, is that some of your loads may be shooting 20 to 100 fps faster from shot to shot. Obviously the slower shots will tend to shoot low, and the faster rounds climb. Not sure of your OAL, but try seating them deeper. I have posted on here before about groupings at longer distance. Talking with guys that shoot competitively suggest seating bullets pretty deep for LRH and target. By this I mean seating .080" to .100" away from the lands. Both my cousin and I did this with VLD type bullets and our groups went from 1MOA to just under .5MOA and better if we do our part. This tightened up our velocities, and fliers went away. He has a 338 Lapua shooting 300SMK's. Believe it or not, his load is 50BMG 93.0grn, with a velocity of 2740 with only about a 5fps spread. I think his long barrel really helps in the consistency of burn out of this slow burning powder. If your current load is shooting well, seating them deeper may hone in your accuracy and tighten up your velocity spread. To eliminate the heat factor, take your time in between shots. I know its tedious, but allow about 3 to 5 minutes between shots after your first 2 shots so that your barrel can stay at a consistent temperature. I have my own speculation, but the hotter the barrel, you can increase case pressure by allowing a casing set to long in a hot chamber. This also increases velocity and causes stringing. Shoot some across a chrony and see what its doing. If you have a large velocity spread, then it you may need to go to a R22, R25, H1000, Retumbo, or Hodgdon or IMR 4831. With the 250's, I would stay with R25, H1000, or the 4831's. Maximum efficiency in a cartridge is between 95% to 100% capacity. Tank [/QUOTE]
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