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Long Range Hunting & Shooting
Necking down 408 cheytac to .338
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<blockquote data-quote="NZ Longranger" data-source="post: 510041" data-attributes="member: 14"><p>Whether there's a need to fire form depends on your version of the 338/408. If its just simply a necked down 375 or 408 with the same or similar shoulder angle in the same position, then your first shot with a projectile is your fire forming. If you're running a much sharper shoulder pushed forward from the original position as Kirby does in his 338AM and we do in the 338 Lunatic, then it certainly is worth fireforming, or just buy Kirby's brass as someone else suggested. Joel, I'm not sure about your shoulder angle and position?</p><p></p><p>We fireform by using any fast burning powder surplus to requirements with half a 4x2 cleaning patch pushed down on top to hold the powder in position. With the current powder we're using up, Viht N320, we use 45gns. We have a fireforming barrel chambered up in all our calibers, so we can run them through without worrying about cooking a good barrel. We have pressure testing equipment hooked up to our fireforming barrels to work out our fireforming loads. The other fillers you hear talked about for this project can produce very erratic and potentially dangerous results. You can get huge pressure spikes with fireforming loads of fast burning powder if you're not paying attention. If you get any of the conventional pressure signs such as any brass flow at all - back off! You are way too hot with any of the 408 brass, especially the older TTI stuff no longer available. Even the Jamieson stuff shows no pressure signs till well over 70,000psi.</p><p>We have found the half patch jammed on top of the powder to be consistent and safe.</p><p>And you're quite right about when you should neck turn. Ideally after you've finished all your necking down and the brass is work hardened. Annealed and soft brass doesn't turn as well and is inclined to gall on the mandrel. The exception to this is some wildcats that need fireforming to position the neck correctly before you can turn them. Some will split shoulders on fireforming if not annealed first, so we anneal, fireform, then turn. The fireforming work hardens the brass sufficiently to allow good neckturning. </p><p>That's our take on it anyway for what its worth!</p><p>Greg</p></blockquote><p></p>
[QUOTE="NZ Longranger, post: 510041, member: 14"] Whether there's a need to fire form depends on your version of the 338/408. If its just simply a necked down 375 or 408 with the same or similar shoulder angle in the same position, then your first shot with a projectile is your fire forming. If you're running a much sharper shoulder pushed forward from the original position as Kirby does in his 338AM and we do in the 338 Lunatic, then it certainly is worth fireforming, or just buy Kirby's brass as someone else suggested. Joel, I'm not sure about your shoulder angle and position? We fireform by using any fast burning powder surplus to requirements with half a 4x2 cleaning patch pushed down on top to hold the powder in position. With the current powder we're using up, Viht N320, we use 45gns. We have a fireforming barrel chambered up in all our calibers, so we can run them through without worrying about cooking a good barrel. We have pressure testing equipment hooked up to our fireforming barrels to work out our fireforming loads. The other fillers you hear talked about for this project can produce very erratic and potentially dangerous results. You can get huge pressure spikes with fireforming loads of fast burning powder if you're not paying attention. If you get any of the conventional pressure signs such as any brass flow at all - back off! You are way too hot with any of the 408 brass, especially the older TTI stuff no longer available. Even the Jamieson stuff shows no pressure signs till well over 70,000psi. We have found the half patch jammed on top of the powder to be consistent and safe. And you're quite right about when you should neck turn. Ideally after you've finished all your necking down and the brass is work hardened. Annealed and soft brass doesn't turn as well and is inclined to gall on the mandrel. The exception to this is some wildcats that need fireforming to position the neck correctly before you can turn them. Some will split shoulders on fireforming if not annealed first, so we anneal, fireform, then turn. The fireforming work hardens the brass sufficiently to allow good neckturning. That's our take on it anyway for what its worth! Greg [/QUOTE]
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Necking down 408 cheytac to .338
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