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What is the advantage to loading long

wade2big

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Minuteman
Sep 16, 2017
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For example, if a rifle shoots well at a 2.80” OAL, what benefit would be gained loading .02” off the lands to 2.86” OAL? Can the small gain in case capacity net a faster velocity within similar pressures using a bit more powder to take up space? I’m assuming this is the same principal just on a smaller scale between a .308 win and a 30/06 or a 6.5CM compared to a 6.5prc. Similar pressures net more velocity in the larger case. It just takes more powder to get it there. Am I on the right track?
 
You may have a broader jump node and or powder charge node at the longer coal. Or the reverse may be true.
 
The three potential advantages in my mind, in order of magnitude, are:

1) Keep the bottom of the bullet bearing surface out of the neck/shoulder junction (not always feasible for longer cartridges in a short action)
2) Bullet might like being closer to the lands (I don’t personally find that seating depth nodes are very far apart, more like 0.010-020” apart, not 0.100” apart)
3) More powder capacity (it takes a LOT of seating depth change to buy enough case capacity to yield meaningful MV increases)
 
More case volume means less pressure which means a smidge more powder for a smidge more velocity potentially. Or the same velocity at a slightly lower pressure.

If you can keep the bullet above the neck shoulder transition then brass migration and pinching is one less thing you can worry about.

I find stuff is most accurate closer to the lands vs large jumps, maybe not as forgiving but more accurate if you can keep it loaded where it’s happy.
 
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