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Rifles, Reloading, Optics, Equipment
Reloading
Seating depth dilemma
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<blockquote data-quote="Bart B" data-source="post: 1125198" data-attributes="member: 5302"><p>That general rule of some caliber, or fraction thereof, for a bullet's heel to be seated that far back from the case mouth has been debunked so many times. I've no idea where that myth came from. Nor has anyone ever made a plausible argument for it based on the physics of what happens when a round's fired. It reminds me of chapter 13 in the book "How To Make Things Do What You Want Them To Do" titled "Electronic Slot Machines." It says to use two fingers touching the screen first in the upper left-hand corner, then the lower right-hand one, then the upper right-hand corner and finally the lower left-hand corner to have the greatest odds of making the next play a winner. I've seen many people in casino's doing that, but some of them insist that order's wrong and a different one is correct.</p><p></p><p>Best proof it's a myth is people getting best accuracy for any given caliber don't use one of those standards such believers specify. Another's Sierra Bullets use of bullets up to 240 grains in the .300 Win Mag test barrel used for all 30 caliber bullet 190 grains and heavier getting 1/2 MOA at worst test groups in their 200 yard range. I've shot bullets from 155 to 220 grains from several 30 caliber cartridges with excellent accuracy with all sorts of seating depths relative to bullet diameter.</p><p></p><p>I suggest seating the bullets so the .300 Win Mag's COL's 1/16th inch shorter than magazine length for good functioning. I did that with a custom barreled .300 Win. Mag with a SAAMI spec chamber with 165 to 220 grain bullets. A wide range of bullet heel location back from the case mouth didn't seem to matter as bullet jump to the lands varied quite a bit and accuracy stayed at the same good level across all; no worse than 1 MOA at ranges 500 yards and further. </p><p></p><p>For single round loading, seat them out to touch the lands which helps center them in the rifling. If they're held with only 1/8th inch of the neck length, so be it. That won't be a pressure problem with reduced loads.</p><p></p><p>Regarding your test groups.... It's my opinion there are no such thing as fliers. All of those shots striking far away from the aiming point went there because the shooting system put them there. All the variables added up in that direction. The ammo, rifle and the thing that aims the rifle comprise the shooting system. It's the thing that holds the rifle that has the widest range of variables. Shoot at least 10 shots per test group. Kudge accuracy by the largest group for a given load fired. A 3-shot group have about a 1 in 5 odds of representing where all shots fired with that load will shoot inside of; it only tells you where those three went.</p></blockquote><p></p>
[QUOTE="Bart B, post: 1125198, member: 5302"] That general rule of some caliber, or fraction thereof, for a bullet's heel to be seated that far back from the case mouth has been debunked so many times. I've no idea where that myth came from. Nor has anyone ever made a plausible argument for it based on the physics of what happens when a round's fired. It reminds me of chapter 13 in the book "How To Make Things Do What You Want Them To Do" titled "Electronic Slot Machines." It says to use two fingers touching the screen first in the upper left-hand corner, then the lower right-hand one, then the upper right-hand corner and finally the lower left-hand corner to have the greatest odds of making the next play a winner. I've seen many people in casino's doing that, but some of them insist that order's wrong and a different one is correct. Best proof it's a myth is people getting best accuracy for any given caliber don't use one of those standards such believers specify. Another's Sierra Bullets use of bullets up to 240 grains in the .300 Win Mag test barrel used for all 30 caliber bullet 190 grains and heavier getting 1/2 MOA at worst test groups in their 200 yard range. I've shot bullets from 155 to 220 grains from several 30 caliber cartridges with excellent accuracy with all sorts of seating depths relative to bullet diameter. I suggest seating the bullets so the .300 Win Mag's COL's 1/16th inch shorter than magazine length for good functioning. I did that with a custom barreled .300 Win. Mag with a SAAMI spec chamber with 165 to 220 grain bullets. A wide range of bullet heel location back from the case mouth didn't seem to matter as bullet jump to the lands varied quite a bit and accuracy stayed at the same good level across all; no worse than 1 MOA at ranges 500 yards and further. For single round loading, seat them out to touch the lands which helps center them in the rifling. If they're held with only 1/8th inch of the neck length, so be it. That won't be a pressure problem with reduced loads. Regarding your test groups.... It's my opinion there are no such thing as fliers. All of those shots striking far away from the aiming point went there because the shooting system put them there. All the variables added up in that direction. The ammo, rifle and the thing that aims the rifle comprise the shooting system. It's the thing that holds the rifle that has the widest range of variables. Shoot at least 10 shots per test group. Kudge accuracy by the largest group for a given load fired. A 3-shot group have about a 1 in 5 odds of representing where all shots fired with that load will shoot inside of; it only tells you where those three went. [/QUOTE]
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