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Punch, Internal LT, Jacket Closer
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Quantity in Basket:
None
Catalog No.: PUNCH-HJ
Price: $144.00
Shipping Weight: 0.20 pounds
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The PUNCH-HJ is a Jacket Tip CLoser internal punch, for the LT-1-H die. It is used instead of a normal lead tip finishing punch, but in the same LT die, to nudge the open tip of a bullet jacket to a smaller meplat or end diameter.
While optimistically called a "tip closer" the operation actually just reduces the tip opening and seldom can completely close it without the force causing a ring in the ogive or even a partial collapse of the ogive. The degree of closure depends on the jacket wall thickness and jacket strength, as well as how much support is inside the ogive from the core. A short core in a long jacket leaves much of the ogive unsupported on the inside. Pressing on the tip to push it closer together transfers force through the unsupported jacket walls in this area, and can buckle the jacket, fold it, or cause a ring to appear at the end of the punch. That is the limit of how far the tip can be closed with that particular jacket and core combination.
But in most cases, the tip opening will close to half or even less of its original diamaeter without any problem. The purpose of the smaller tip is to increase the bullet BC or ballistic coefficient, meaning the ratio of how well that bullet passes through the atmosphere and retains its energy compared to an agreed standard bullet design. The tip closure is often largely cosmetic, having some effect on BC but a vastly greater effect in the mind of the user of that bullet. It just "looks better" to many shooters, so for that reason alone, the tip closer punch can be a benefit to bullet makers. The improvement in BC may or may not be significant but it doesn't hurt!
One caliber of LT-1-H die can be used with any ogive shape of internal punch. Normally a sharp ogive shape, like the 6-S and longer radius tangent ogives, or the compound (hybrid) tangent/secant shapes, or the conventional secant shapes used in long range shooting, are the best candidates for this treatment. More blunt nose shapes such as the 1-E and 3/4-E, the 2-S and 4-S and similar short nose shapes, usually don't benefit enough to justify the investment, or, in some cases, simply won't work with this style of punch. The angle within the ogive cavity is not cut the same as in a typical lead tip finisher. It is made with a slighty more obtuse included angle, so that the end of the jacket strikes first and is pushed inward, toward the bullet centerline, by a portion of the vectored axial force. This makes a very faint difference in the shape of the curve, if one looks closely enough to see it. But otherwise, the ogive would simply match the shape of the cavity and the punch would vector all the force straight along the axis. This would not close the tip, but would move a portion of the ogive straight back, creating a step in the nose.
Because the force is all applied, initially, to the edge of the jacket, any abrasion from airborne dust and grit that lands on components and lube containers will be more effective at lapping the punch cavity at the point of contact. Therefore, not only is the punch made with a different angle or curve than a standard lead tip punch, but it is made from much harder and more abrasion resistant material, with a different heat treatment process. (Lead tip finishing dies and standard punches run under such low pressure concentrations that they will last virtually forever even if not hardened. Their only job is to reshape a bit of soft lead at the tip.)
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