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Rifles, Reloading, Optics, Equipment
Reloading
Badlands BD-2 load data
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<blockquote data-quote="nralifer" data-source="post: 2770684" data-attributes="member: 94556"><p>This next blog describes our experience with keeping necks straight during the sizing process. Any comments by contributors to this site on this subject are very welcomed. So here goes. All these observations were done in the 338 Lapua Mag case using Lapua brass. </p><p>Accuracy of copper bullets is quite dependent on alignment of the bullet to the rifling. A bullet entering the rifling eccentrically will move down the barrel eccentrically and proceed throughout it's flight with more precessional motion than is required by the twist rate of the barrel. This is not good for accuracy or BC, both will be degraded. Having the case aligned with the barrel central axis AND having the bullet alined to the central axis of the case is paramount to maximal accuracy and BC. A misaligned neck will misalign the bullet to the rifling. On the first firing, a piece of brass's neck is not only expanded to that of the chamber neck diameter, but also now is almost perfectly alined to the rifle central axis. The trick in reloading is resizing that brass's body and neck without changing that alignment, then seating a bullet as straight as possible in the neck. </p><p>Resizing the brass involves several goals. The first is reducing the body diameter sufficiently to allow enough clearance with the chamber to make bolt closure easy. The second is pushing the shoulder back 0.001-0.003" to achieve the proper head space but not work the brass excessively to cause excessive stretching and contraction at the base/body junction which will fatigue the brass there and eventually lead to a case head separation. The third is to narrow the neck diameter sufficiently to achieve enough neck tension to hold the bullet firmly enough in the neck to resist recoil forces of the rifle while in the magazine to not allow the bullet to move within the neck. </p><p>We are finding that neck alignment is best preserved if this resizing process is broken up into three steps. The first is body resizing simultaneously with shoulder bump WITHOUT RESING THE NECK. This is best accomplished with a dedicated body sizing die whose neck diameter will not narrow the neck diameter of the brass. The next step is to BEGIN to narrow the neck and remove the spent primer. I remove the expander ball so as not to touch the neck. I use a full length sizing die whose neck is honed to 0.363" diameter and whose shoulder area DOES NOT touch the shoulder by about 0.040" or so. The last step is to use again a full length sizing die whose neck area has been honed to 0.360-0.358." The rationale here is twofold. The first is by progressively narrowing the neck the brass there is not "worked" too quickly. We have seen that neck runout can increase to 0.003-0.005" if neck resizing is done too quickly. Using an expander ball can improve this runout some but not enough consistently. The second reason is that by leaving a portion of the neck base close to or at the chamber neck diameter helps align the cartridge to the rifle bore and offset the slight misalignment that plunger ejectors induce by canting the case upon full bolt closure. </p><p>One crucial point is you will need 1 or 2 custom honed full length sizing dies. I have had absolutely superb service in this regard from Forster. I have no connection to the company, but I simply think their customer service us absolutely superb and their pricing is reasonable.</p><p></p><p>Using this method of resizing we are able to keep neck runout to 0.00125" or less assuming we use brass with circumferentially uniform neck wall thickness. Last point is that the neck mouth is chamfered lightly with a chamfering tool. I like Lyman's hand chamfering tool. If one finds that neck turning is necessary to even up the neck thickness circumstantially, do the turning AFTER the first firing and BEFORE any attempt to resize. A double cutting dedicated electrical mini lathe is the best tool for the job, but it is a bit expensive. If you start out with high quality brass you may not need it.</p></blockquote><p></p>
[QUOTE="nralifer, post: 2770684, member: 94556"] This next blog describes our experience with keeping necks straight during the sizing process. Any comments by contributors to this site on this subject are very welcomed. So here goes. All these observations were done in the 338 Lapua Mag case using Lapua brass. Accuracy of copper bullets is quite dependent on alignment of the bullet to the rifling. A bullet entering the rifling eccentrically will move down the barrel eccentrically and proceed throughout it’s flight with more precessional motion than is required by the twist rate of the barrel. This is not good for accuracy or BC, both will be degraded. Having the case aligned with the barrel central axis AND having the bullet alined to the central axis of the case is paramount to maximal accuracy and BC. A misaligned neck will misalign the bullet to the rifling. On the first firing, a piece of brass’s neck is not only expanded to that of the chamber neck diameter, but also now is almost perfectly alined to the rifle central axis. The trick in reloading is resizing that brass’s body and neck without changing that alignment, then seating a bullet as straight as possible in the neck. Resizing the brass involves several goals. The first is reducing the body diameter sufficiently to allow enough clearance with the chamber to make bolt closure easy. The second is pushing the shoulder back 0.001-0.003” to achieve the proper head space but not work the brass excessively to cause excessive stretching and contraction at the base/body junction which will fatigue the brass there and eventually lead to a case head separation. The third is to narrow the neck diameter sufficiently to achieve enough neck tension to hold the bullet firmly enough in the neck to resist recoil forces of the rifle while in the magazine to not allow the bullet to move within the neck. We are finding that neck alignment is best preserved if this resizing process is broken up into three steps. The first is body resizing simultaneously with shoulder bump WITHOUT RESING THE NECK. This is best accomplished with a dedicated body sizing die whose neck diameter will not narrow the neck diameter of the brass. The next step is to BEGIN to narrow the neck and remove the spent primer. I remove the expander ball so as not to touch the neck. I use a full length sizing die whose neck is honed to 0.363” diameter and whose shoulder area DOES NOT touch the shoulder by about 0.040” or so. The last step is to use again a full length sizing die whose neck area has been honed to 0.360-0.358.” The rationale here is twofold. The first is by progressively narrowing the neck the brass there is not “worked” too quickly. We have seen that neck runout can increase to 0.003-0.005” if neck resizing is done too quickly. Using an expander ball can improve this runout some but not enough consistently. The second reason is that by leaving a portion of the neck base close to or at the chamber neck diameter helps align the cartridge to the rifle bore and offset the slight misalignment that plunger ejectors induce by canting the case upon full bolt closure. One crucial point is you will need 1 or 2 custom honed full length sizing dies. I have had absolutely superb service in this regard from Forster. I have no connection to the company, but I simply think their customer service us absolutely superb and their pricing is reasonable. Using this method of resizing we are able to keep neck runout to 0.00125” or less assuming we use brass with circumferentially uniform neck wall thickness. Last point is that the neck mouth is chamfered lightly with a chamfering tool. I like Lyman’s hand chamfering tool. If one finds that neck turning is necessary to even up the neck thickness circumstantially, do the turning AFTER the first firing and BEFORE any attempt to resize. A double cutting dedicated electrical mini lathe is the best tool for the job, but it is a bit expensive. If you start out with high quality brass you may not need it. [/QUOTE]
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Badlands BD-2 load data
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