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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Anyone own a 7mm 300 Win Mag?
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<blockquote data-quote="Kiwi Nate" data-source="post: 1764288" data-attributes="member: 8533"><p>Hi Brian, on your unknown, I suggest you start with a Hornady 7mm Mag neck die. this differs to the regular Hornady 7mm neck die. The 7mm Mag neck die has both body and shoulder clearance to cope with a range of case styles. Its not the most ideal die for match level concentric ammo but it is the correct die for this task.</p><p></p><p>Once you have the die (or die set), you can tentatively set about necking down a few .300 WM cases. size the necks down until the case fits snuggly in the chamber of the rifle. Do not simply try to wind the die down to the shell holder as this die is designed for shorter cases like the 7mm WSM. Perform this task incrementally until the case fits the chamber.</p><p></p><p>Following this, I suggest you fireform using Trail Boss Powder. this will ensure that you are able to form a case without any risk to yourself. 28 grain TB behind a 160-162gr bullet will produce about 1700fps.</p><p></p><p>Once you have fire formed cases, you can try sizing a case again. Ideally, the case should then be run over a concentricity gauge such as a Sinclair, just to see how much distortion occurs within the case. If the die (and seating) works for you, producing concentric ammo, you can carry on with it. If not, you will most likely now need to move on to another brand of die. However, you must take stock of the fact that the Redding for example, only partially sizes the neck of the .300 WM. If your case has a 40 degree shoulder, you will end up sizing even less of the neck after fitting a 7mm bushing to the .300 die.</p><p></p><p>It is important to understand what dimensions you are dealing with first before going too much further ahead. A cerafide cast would be ideal but this is the modern internet / forum world where folk are just as likely to say thanks for the advice and then do nothing about it. The Hornady die is the easiest way for you to get into this.</p></blockquote><p></p>
[QUOTE="Kiwi Nate, post: 1764288, member: 8533"] Hi Brian, on your unknown, I suggest you start with a Hornady 7mm Mag neck die. this differs to the regular Hornady 7mm neck die. The 7mm Mag neck die has both body and shoulder clearance to cope with a range of case styles. Its not the most ideal die for match level concentric ammo but it is the correct die for this task. Once you have the die (or die set), you can tentatively set about necking down a few .300 WM cases. size the necks down until the case fits snuggly in the chamber of the rifle. Do not simply try to wind the die down to the shell holder as this die is designed for shorter cases like the 7mm WSM. Perform this task incrementally until the case fits the chamber. Following this, I suggest you fireform using Trail Boss Powder. this will ensure that you are able to form a case without any risk to yourself. 28 grain TB behind a 160-162gr bullet will produce about 1700fps. Once you have fire formed cases, you can try sizing a case again. Ideally, the case should then be run over a concentricity gauge such as a Sinclair, just to see how much distortion occurs within the case. If the die (and seating) works for you, producing concentric ammo, you can carry on with it. If not, you will most likely now need to move on to another brand of die. However, you must take stock of the fact that the Redding for example, only partially sizes the neck of the .300 WM. If your case has a 40 degree shoulder, you will end up sizing even less of the neck after fitting a 7mm bushing to the .300 die. It is important to understand what dimensions you are dealing with first before going too much further ahead. A cerafide cast would be ideal but this is the modern internet / forum world where folk are just as likely to say thanks for the advice and then do nothing about it. The Hornady die is the easiest way for you to get into this. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Anyone own a 7mm 300 Win Mag?
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