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Rifles, Reloading, Optics, Equipment
Reloading
lapua brass prep
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<blockquote data-quote="Mikecr" data-source="post: 366916" data-attributes="member: 1521"><p>I had a Browning A-Bolt rebarreled to 6br Norma.</p><p>This was a case where I didn't design & hold the reamer. I let the gunsmith use his given that it's enough challenge just to rebarrel a Browning(extended tennon, epoxied, interference fit). This was J.Kolbe, and he did an incredible job on the chamber, fit & finish.</p><p>Anyway, Jim says it's a bit tight. </p><p>So I turn a culled case neck to an even .013" thickness, seat a bullet and try chambering(it failed to do so). I turn another to .0125" thick and find that it chambers ok.</p><p>So..</p><p>No-Go case = .269 NK(.013 thick, x2, +.243)[Chamber Neck]</p><p>Go case = .268 NK(.0125 thick)</p><p>For 1.5thou total clearance, I need to take necks to .0115" thick(.2665 loaded neck).</p><p></p><p>For 1thou of tension on .2665 necks, I need a .265 bushing, which accounts for .0005 of springback on my sizing. .2665-.265= .0015-.0005= .001 tension.</p><p>For reloading, I'll be using standard Wilson dies on this one.</p><p>I pickup a Redding titanium nitrided bushing in .265 and drop it in the neck die.</p><p></p><p>I use Lapua brass in 6br & I have a bunch. I picked out 200cases with low thickness variance(360deg). Of these the brass measured ~13.5thou thick, so it's an easy turn. </p><p>After fire-forming I lost only 7cases to H20 capacity differences. </p><p>That leaves me 193 diamonds. Plenty enough.</p><p></p><p>After a few firings, I sent several cases & a Redding body die to JLC Precision for minimal sizing/bumping.</p><p>This chamber & system has produced the lowest loaded round TIR that I have ever measured. It's low 10thous and prepolishing is required to see runout over surface noise.</p><p></p><p>This was a basic plan, far easier than required for a wildcat.</p><p>You can scratch it out on paper before ever beginning, but to do so you need all the brass your going to use for a barrel -in hand, so that you can measure it.</p><p>Similar plans are needed for a gun build from scratch, and this all begins with a bullet.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 366916, member: 1521"] I had a Browning A-Bolt rebarreled to 6br Norma. This was a case where I didn't design & hold the reamer. I let the gunsmith use his given that it's enough challenge just to rebarrel a Browning(extended tennon, epoxied, interference fit). This was J.Kolbe, and he did an incredible job on the chamber, fit & finish. Anyway, Jim says it's a bit tight. So I turn a culled case neck to an even .013" thickness, seat a bullet and try chambering(it failed to do so). I turn another to .0125" thick and find that it chambers ok. So.. No-Go case = .269 NK(.013 thick, x2, +.243)[Chamber Neck] Go case = .268 NK(.0125 thick) For 1.5thou total clearance, I need to take necks to .0115" thick(.2665 loaded neck). For 1thou of tension on .2665 necks, I need a .265 bushing, which accounts for .0005 of springback on my sizing. .2665-.265= .0015-.0005= .001 tension. For reloading, I'll be using standard Wilson dies on this one. I pickup a Redding titanium nitrided bushing in .265 and drop it in the neck die. I use Lapua brass in 6br & I have a bunch. I picked out 200cases with low thickness variance(360deg). Of these the brass measured ~13.5thou thick, so it's an easy turn. After fire-forming I lost only 7cases to H20 capacity differences. That leaves me 193 diamonds. Plenty enough. After a few firings, I sent several cases & a Redding body die to JLC Precision for minimal sizing/bumping. This chamber & system has produced the lowest loaded round TIR that I have ever measured. It's low 10thous and prepolishing is required to see runout over surface noise. This was a basic plan, far easier than required for a wildcat. You can scratch it out on paper before ever beginning, but to do so you need all the brass your going to use for a barrel -in hand, so that you can measure it. Similar plans are needed for a gun build from scratch, and this all begins with a bullet. [/QUOTE]
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