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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Throating ?'s
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<blockquote data-quote="Coyboy" data-source="post: 324998" data-attributes="member: 3733"><p>Roy, most sammi spec factory chambers and reamers have a lead angle of 3 degrees, this would be the tapered portion of the cut that makes a "ramp" out of the lands for the bullet to engrave on.</p><p></p><p>Almost all "match reamers" will be ground with a 1.5 degree lead angle. </p><p></p><p>When a reamer is made the purchaser can spec whatever lead angle they want, and Kiff will grind it. I have a couple of reamers of Aarons design for the 7mm RM that have 3/4 degree lead angles, obviously designed for the bergers.</p><p></p><p>So from this description it is apears that the sammi spec for you basic cartriges designed for standard factory ammo have the steepest angle which would better match the olgive of most standard factory bullets while the shallow angles are used with the high bc low drag bullets.</p><p></p><p>I think that the bigger factor may be lower initial pressures with the shallower angles, this may well cut down on the engraving force of the bullet to the rifling, I have a few hunting rifles in standard offerings that have the 3 degree lead and they do shoot as well as any.</p></blockquote><p></p>
[QUOTE="Coyboy, post: 324998, member: 3733"] Roy, most sammi spec factory chambers and reamers have a lead angle of 3 degrees, this would be the tapered portion of the cut that makes a "ramp" out of the lands for the bullet to engrave on. Almost all "match reamers" will be ground with a 1.5 degree lead angle. When a reamer is made the purchaser can spec whatever lead angle they want, and Kiff will grind it. I have a couple of reamers of Aarons design for the 7mm RM that have 3/4 degree lead angles, obviously designed for the bergers. So from this description it is apears that the sammi spec for you basic cartriges designed for standard factory ammo have the steepest angle which would better match the olgive of most standard factory bullets while the shallow angles are used with the high bc low drag bullets. I think that the bigger factor may be lower initial pressures with the shallower angles, this may well cut down on the engraving force of the bullet to the rifling, I have a few hunting rifles in standard offerings that have the 3 degree lead and they do shoot as well as any. [/QUOTE]
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