308 x 1.365 jacket, pk/250
	Quantity in Basket: None Catalog No.: J-30-136 Price: $75.00 Shipping Weight: 1.50 pounds 168 available for immediate delivery
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This is a long, straight-wall 30 caliber jacket with mouth to base taper (that is, no step as with our 1.25 VB jackets). The 1.365 inch length is suitable for either very heavy round nose subsonic bullet designs, or for long range, high BC bullets of the Ultra Low Drag (ULD) and similar styles. For those who want a little more weight than can be achieved with an open tip style in our J-30-125 jackets, this adds over 1/10 inch more jacket length. The jacket weighs 50.8 grains, and has a tapered wall for expansion control. The mouth (or 1/8 inch back from the opening) has a 0.015 wall thickness. The midpoint of the jacket has .270-inch ID, and just above the solid base the OD is .264 inches. The wall thickness at the base is aproximately 0.022 inches, and the wall thickness at midpoint is aproximately 0.018 inches. A 0.264 core fits to the bottom but a .250-.251 diameter core is better for bonding and for not trapping any air below it during seating. The standard core diameter for Corbin jackets is .250/.251 and is made using .247-inch lead wire or core mold, which is then swaged up to .250 in the core swage die. These jackets are packaged in reclosable zip-seal heavy duty (4 mil) poly bags of 250 jackets each. As with all our jackets, the diameter is about two thousandths smaller than the finished bullet will be, to allow the core to expand the jacket during core seating. This provides an extremely good grip between the core and jacket ID, so that the jacket does not spin independently from the core (which is called "core slippage"). Most of the .308 diameter bullets are made using a .306 to .307 diameter jacket. Because jackets are expanded in diameter during core seating for a tight core/jacket grip, the core seating punch which fits into the jacket (for open tip or OT-HP style bullets) must necessarily be a very tight press fit into the jacket. If it were an easy slip fit, as soon as pressure was applied, the jacket would begin to expand toward the core seat die ID, and this would allow lead to flow past the punch, immediately reducing the seating pressure. Two symptions would be undersized bullets and a visible flashing of lead around the seating punch. The need to have the seating punch maintain a high pressure seal against the lead core even as the jacket finishes expanding means that the jacket will be a very tight fit to the punch. It might be difficult to insert the punch by hand, for example. Since the jacket will expand about 0.001 to 0.002 inches during core seating, this means the seating punch will need to be that much larger than the initial ID of the jacket to keep a good pressure seal. Handloaders who are new to bullet swaging often try the punch by hand into the jacket and immediately conclude it is "too big". However, the need for a pressure sealing core seat punch also causes a problem: the jacket is force fitted to the punch by the power of the swage press, so the punch and jacket want to "stick" together as you lower the press ram. This pulls the jacket and core out of the die, and leaves them stuck on the seating punch. The solution has three parts: Use little or no lube on the outside of the jacket (only for core seating!) Wipe a film of lube on the seating punch before you push it into the jacket. Hold the pressure of seating the core for a second or two longer, to make sure that the jacket and core expand firmly in the die. This procedure increases friction between the die ID and the jacket OD, reduces friction between the punch OD and the jacket ID, and lets the metal flow and expand fully to insure that the jacket OD expands fully against the die walls, while allowing a very small amount of lead to try to seep past the tip of the punch and push the jacket away from the punch OD. The only thing that removes the jacket and core from the seating punch is the frictional grip of the die on the jacket. And the only way to get that is to fully expand the jacket so it presses firmly against the die walls. This means that if you gingerly ease the press handle down and are over cautious about applying enough pressure to the core, the jacket and core will not fully expand. Yet the punch will be forced firmly into the open jacket mouth and will be held firmly by the slightly expanded jacket. If you stick a jacket on the punch, you may be able to remove it simply by wiping the lube off the outside of the jacket, wiping the die bore clean of lube with a cotton swab stick, and swaging it again with a little more pressure and a little longer time. But do not use a massive force, as that will simply crack the die apart or bend the punch! The right amount of force to use is learned by experience, working your way up from the point where the jacket sticks on the punch to the point where the jacket expands enough to stay in the die. This is true for all jackets, and for both flat base and rebated boattail jacketed bullets. But the amount of pressure varies with the jacket thickness, length, hardness, caliber, core length, and the base style, and will require a little experimenting to discover the perfect amount for a given bullet. Bullet swaging is primarily a science, which can be done by the numbers, but it has an element of art or skill, which must be done by developing some craftsmanship. That comes with experience. Once you undetstand the basic procedure and know why things are done a certain way, you then can apply variations of the quantities, adjusting the measurement so to speak, while staying within the procedural guidelines that lead to success. Most bullet jackets have thicker walls as they approach the solid or closed end. Usually this is the base of the bullet (FMJ styles may reverse the jacket). The thicker walls mean that the ID becomes a little smaller toward the jacket base. So if the lead core weight (and length) is such that the core is seated near the mouth, the ID will be a little larger and require a larger diameter core seat punch for a good seal as compared to a shorter, lighter core that needs to be seated closer to the base. In general, most jackets can use one diameter punch over a reasonable range of weights for the core because their wall taper is slight. But if the taper is somewhat greater, or the jacket wall is stepped in thickness, then a smaller core seating punch is required for shorter cores. Pin gauges are a good way to measure the ID of a jacket and determine the taper. If you have a pin gauge set and find that a 0.2770 pin fits reasonably well near the jacket mouth, but only goes about a quarter of the distance to the jacket base before it stops against the jacket ID, and a 0.265 pin fits all the way to the bottom with just a tiny bit of drag at the base, then you know the jacket has an average taper of half the difference between the two diameters. That is .2770 - .2650 = 0.012 inches difference, and that is divided by two jacket walls, so it means each wall tapers by 0.006 inches top to bottom. Or close enough for practical purposes. If the jacket happens to measure 0.3065 inches on the OD, and a 0.2770 pin fits closely near the mouth area, that means by the time you seat the core and expand the jacket to 0.3079 inches (usually that's what a .308 diameter would be prior to finishing in the point form die), the jacket will expand by 0.3079 - 0.3065 = 0.0014 inches. Therefore, the ID will become 0.2770 + 0.0014 = 0.2784 inches. And THAT is the size of the seating punch you'd need to maintain a good pressure seal instead of the easiy fit of the 0.2770 gauge pin. Do the same math for the smaller ID at the base, and you'll see that a smaller core seat punch would be required to maintain a seal, and yet not "plow into" the jacket itself -- which is a way to stick the punch and jacket so that the lubrication/timing/pressure technique no longer solves the problem! In this case, the problem is solved by using a smaller punch (plus the lube/timing/pressure procedure). The point is that the immediate reaction of beginning swagers in calling for a smaller punch is usually not the solution to a sticking jacket, but in certain special circumstances where the right punch for the heavier core is too large for a short core further down in the same jacket (or with a thicker jacket) a smaller punch really is the right answer! It depends on the context.