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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Case length reduction upon fire forming Improved cartridges?
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<blockquote data-quote="Steve Shelp" data-source="post: 25918" data-attributes="member: 22"><p>Brent,</p><p> I asked around and nobody is reporting anymore than .020" shortening on thier cases. There were (3) 338 Lapua Improved rifles and (1) 300 Lapua Improved fired yesterday. I asked each one of them and Dave also.</p><p> It was recommended to make the reamer length .005" over the max case length. So 2.720" + .005.</p><p> The gap created really doesn't cause any problems except when you don't keep it cleaned out and carbon builds up in there.</p><p> I did have this happen to me last year to where eventually I couldn't chamber a round. I explained this in a previous post months back to CrowMag, I beleive it was, if you want to reference back to it. So if you keep the throat area cleaned up from carbon buildup, it's not really a problem. </p><p> But you can't make the chamber shorter to begin with to compensate for the shorting upon firing, because the .020 or .030" shorting is going to happen no matter from where you start. If you trim brand new case back enough to fit into the shoter chamber they are simply going to shorten up .020 to .030 from that point instead of the 2.720 of a brand new case. </p><p> So me personally, I would keep the chamber as long as possible and keep the shorting of the case to the maximum possible length. </p><p> Remember if you don't end up with a .270" long neck with this 338, it isn't as critical as say a 22 or 24 caliber rifle. The surface area in contact with the bullet is much larger with the larger diameter bullets. So there is plenty of neck tension to hold the bullet if your neck ends up .010" or so shorter than what you originally planned for. My opinion only for what you think it's worth. </p><p> The only way around this would be to have a blow out chamber that is cut around 2.720+... fire the case to blow it out and shorten the case up.... OAL trim the case to the shorter dimension... let's say 2.695".... then have your actual rifle chamber cut with at 2.700" OAL reamer. But that would take 2 reamers and second barrel/chambering and a lot of work for no improvement in accuracy or functionality IMO.</p><p></p><p>We did ok yesterday. Didn't win anything, but I felt good with my results in the conditions that I shot in and compared to others in my relays. The 338 did a lot better than I expected.</p><p></p><p>Talk to you later!</p><p>Steve</p><p></p><p>[ 03-16-2003: Message edited by: Steve Shelp ]</p></blockquote><p></p>
[QUOTE="Steve Shelp, post: 25918, member: 22"] Brent, I asked around and nobody is reporting anymore than .020" shortening on thier cases. There were (3) 338 Lapua Improved rifles and (1) 300 Lapua Improved fired yesterday. I asked each one of them and Dave also. It was recommended to make the reamer length .005" over the max case length. So 2.720" + .005. The gap created really doesn't cause any problems except when you don't keep it cleaned out and carbon builds up in there. I did have this happen to me last year to where eventually I couldn't chamber a round. I explained this in a previous post months back to CrowMag, I beleive it was, if you want to reference back to it. So if you keep the throat area cleaned up from carbon buildup, it's not really a problem. But you can't make the chamber shorter to begin with to compensate for the shorting upon firing, because the .020 or .030" shorting is going to happen no matter from where you start. If you trim brand new case back enough to fit into the shoter chamber they are simply going to shorten up .020 to .030 from that point instead of the 2.720 of a brand new case. So me personally, I would keep the chamber as long as possible and keep the shorting of the case to the maximum possible length. Remember if you don't end up with a .270" long neck with this 338, it isn't as critical as say a 22 or 24 caliber rifle. The surface area in contact with the bullet is much larger with the larger diameter bullets. So there is plenty of neck tension to hold the bullet if your neck ends up .010" or so shorter than what you originally planned for. My opinion only for what you think it's worth. The only way around this would be to have a blow out chamber that is cut around 2.720+... fire the case to blow it out and shorten the case up.... OAL trim the case to the shorter dimension... let's say 2.695".... then have your actual rifle chamber cut with at 2.700" OAL reamer. But that would take 2 reamers and second barrel/chambering and a lot of work for no improvement in accuracy or functionality IMO. We did ok yesterday. Didn't win anything, but I felt good with my results in the conditions that I shot in and compared to others in my relays. The 338 did a lot better than I expected. Talk to you later! Steve [ 03-16-2003: Message edited by: Steve Shelp ] [/QUOTE]
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Case length reduction upon fire forming Improved cartridges?
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