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rg1 · November 29, 2015, 01:17 PM

When I first got my Weatherby 300 Magnum I full-length resized with firm contact between die and shellholder. I simply thought it headspaced off the belt. I was only getting 3-4 loadings with factory Weatherby brass until a stretch ring was obvious on the inside of the case. Found out you have to headspace off the shoulder too and I was pushing the shoulders back too far. The stretching and possible case separations are just in front of the belt. Buy a headspace gauge such as Hornady's Headspace Gauge Set to measure how much you push the shoulder back on cases fired in your rifle so the case will headspace on the shoulder 1st and also on the belt. You only want to push the shoulder back about .002" from fired dimensions. Some recommend a special belted case die by Larry Willis but I have no problems adjusting my full length sizing die with no chambering issues. Of course neck sizing for cases fired in your rifle will not cause case stretching but you will have to full length size after a couple rounds fired or possibly a few more with less than maximum loads. I'd recommend full length sizing for hunting rounds when you definitely don't want a failure to chamber.

November 29, 2015, 01:17 PM	#2
rg1 Senior Member Join Date: November 6, 2001 Posts: 1,125	When I first got my Weatherby 300 Magnum I full-length resized with firm contact between die and shellholder. I simply thought it headspaced off the belt. I was only getting 3-4 loadings with factory Weatherby brass until a stretch ring was obvious on the inside of the case. Found out you have to headspace off the shoulder too and I was pushing the shoulders back too far. The stretching and possible case separations are just in front of the belt. Buy a headspace gauge such as Hornady's Headspace Gauge Set to measure how much you push the shoulder back on cases fired in your rifle so the case will headspace on the shoulder 1st and also on the belt. You only want to push the shoulder back about .002" from fired dimensions. Some recommend a special belted case die by Larry Willis but I have no problems adjusting my full length sizing die with no chambering issues. Of course neck sizing for cases fired in your rifle will not cause case stretching but you will have to full length size after a couple rounds fired or possibly a few more with less than maximum loads. I'd recommend full length sizing for hunting rounds when you definitely don't want a failure to chamber. Last edited by rg1; November 29, 2015 at 01:29 PM.