7mm-08 reloads extraction issue - thoughts please

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Originally Posted by caberslash

If you are wondering why the cartridges chamber OK but difficult to extract... physics textbook and the bit about Archimedes and levers/leverage.

After the case has fired, you don't always get sufficient brass springback if the fit was tight to begin with.

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Well I did abandon physics in Form 6 as neither my head nor my math was up to it, but happy to take you word for it. The dealer agrees with you and in a nutshell offered the the 3 lug bolt design found on the Ruger, and other rifles, is inclined to produce this extraction issue when, like you say, brass is resized enough to chamber but not sufficiently at the last few mm of the base which expands to cause a bind. A 2 lug like a Mauser design has a lot more extraction power, apparently. So the fix according to the dealer is to look for issues like the press is not sufficiently anchored to prevent "bounce" and incomplete FL sizing, operator error, slightly overspec dies. He didn't say but probably case brass variations also. Anyway, he is lending me a set of used Hornady dies to try something different. Not having a small base die. After that it will be sending some off to @sneeze to run thru his. We are marking the cases that won't extraction until they cool.

Interesting problem. Thanks for all the input. Will update.

Greetings @Jhon and all,
A couple of observations that may not have been covered. First the 129 grain Hornady projectile is noted as being soft and needs a little more powder to develop the same velocity. From your OP I gather these gave no problems. From my measurements the 139 grain SST is around 2mm longer so may develop a little more pressure due to the reduced case volume. Hodgdon lists 42.2 grains as max for the 140 grain A Frame and Nosler lists 42 grains for their generic 140 grain data. This leads me to believe that 42 grains may be a more sensible max for the SST projectiles. The likely lack of primary extraction has been well discussed and may be inherent with the rifle. This leaves the cases. Each time a case is sized the worked section of the brass becomes a little harder. The same thing happens when it is fired. This may explain the return of sporadic problems with case sticking.
Hope this helps. GPM.

Pretty interesting thread.