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Joined: Feb 2011
Posts: 386
Campfire Member
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Campfire Member
Joined: Feb 2011
Posts: 386 |
Sometimes a phenomenon occurs in which the shoulder is driven back ever so slightly, allowing the case to eventually fail if subjected to full pressure loads after having had numerous low pressure loads put through it.. Thanks
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Joined: Jan 2004
Posts: 163
Campfire Member
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Campfire Member
Joined: Jan 2004
Posts: 163 |
Shoulder setback is caused by both the firing pin hitting the case and the primer igniting, driving the case forward. Under normal pressures, the case expands to fill the chamber and the shoulder returns to nominal. Low-pressure rounds won't expand the case enough and the shoulder stays back, creating excessive headspace. This is what happened to my .250-3000 cases; after a dozen or so cast bullet loadings, I went to full-power jacketed loads and there were several partial head separations upon firing. No harm done to the gun, but it could have been worse.
Dan
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Joined: May 2011
Posts: 218
Campfire Member
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OP
Campfire Member
Joined: May 2011
Posts: 218 |
Some of the low velocity rounds are still producing a high CUP pressure because of the use of faster burning powders. For 300sav, a Lyman 311291 and SR4759 @ 20grns yields a velocity of 1888fps @ 28,800CUP (Lyman's Cast Bullet Handbook). Just going up to 22.5gns of SR4759 takes it up to 2047fps @ 40,200CUP. I'm sure the variables are endless but I wonder at what pressure does the problem start to occur.
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Joined: Nov 2005
Posts: 23,138 Likes: 6
Campfire Ranger
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Campfire Ranger
Joined: Nov 2005
Posts: 23,138 Likes: 6 |
I honestly don't know, but I'll guess that 20,000+psi should overcome it. Just set aside some cases strictly for use with low vel loads and keep them as such.
Last edited by gnoahhh; 08/21/11.
"You can lead a man to logic, but you cannot make him think." Joe Harz "Always certain, often right." Keith McCafferty
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Joined: Nov 2010
Posts: 3,153
Campfire Tracker
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Campfire Tracker
Joined: Nov 2010
Posts: 3,153 |
You should also try moderate loads of 3031 under a 170 gr. flatpoint .30-30 bullet. I use these in both my .300 (sadly not a Savage) and my .30-40s. Very accurate and really kill deer/pigs at iron sight ranges; sort of a ".30-30+P" load.
The little extra velocity ensures that the 170 gr. opens up very reliably and the 170s have always penetrated well, even at .30-30 carbine velocities.
Was Mike Armstrong. Got logged off; couldn't log back on. RE-registered my old call sign, Mesa. FNG. Again. Mike Armstrong
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