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Posted: 8/10/2013 8:36:21 AM EDT
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Hey Guys,
I was curious at what point pressure starts to increase as you move the bullet closer to the lands? For instance, I've got a factory barreled 700 30-06 that I've hand loaded for, for several years. I'm running 56gr of IMR4350 behind a 165 Hornady interlock and had been seating at the spec of 3.30 COAL. These rounds are usually around 1/2 inch at 100 yards and I'm not getting any pressure signs etc; it's a hunting gun so I'm good with that. That said, I was bored and I finally got around to putting my stoney point OAL gauge up to it, and it looks like I'm touching the lands right at 3.40 even. My plan was to cook up some rounds at 3.385 or 3.390 using that same 56gr charge (58gr being the book max) and start from there. Obviously the bullet will come into contact with the lands quicker, but I'm assuming that since it's not starting out jammed it shouldn't increase pressure too drastically? Perhaps a better way to put it is I won't need to back the charge of if I'm still that far away from rifling. Can anyone provide some feedback or thoughts on this? Thanks, Mike M. |
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Actually some guys go this route;
load to the lands or a few thousandths into the lands, work up to pressure signs, note the powder charges previous to the pressure signs, that's the max charge for that gun and bullet and casing combo. All your loading after that should be that charge or lower. This way you'd be pretty well insured against an overcharge/overpressure situation while you vary jump to the lands and powder charges (downward). Change in components and you'd have to redo it. Of course if you seat way too deeply into the case you could also get raises in pressure that way but who the hell loads rounds stupid deep on purpose. I can't say exactly what jump or jam has the highest pressure of all component ceterus parabus and all that. It would depend on the rifle, cartridge and the actual chamber dimensions cut into the barrel. I could be wrong but a very slight jump could be higher than the jam in some instances with some powder. It's been a year since I read on the topic online where shooters on sniper's hide or links from there were talking on the exact happenings with a strain gage equipped rifle. My memory isn't crystal clear on that. |
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Mike,
Reworking is not as involved as it sounds. You say you are 2gr under max now. All you need to do is load maybe 3 rounds starting 3g below your current load or book start what ever is higher. Then fire them and check for pressure signs. I think you will end up right back at your load but its always better to be safe. SteelonSteel's advice is good also but will involve more shooting. |
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