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Rifles, Reloading, Optics, Equipment
Reloading
Developing Load for 168 Berger New Brass vs Once Fired
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<blockquote data-quote="Bart B" data-source="post: 655830" data-attributes="member: 5302"><p>First, the appearance, shape and other visible things on a fired case are typically a poor indicator of actual peak pressures developed. Most folks loading their own belted cases end up with pressures higher than SAAMI specs suggest. If ones load data matches what was published someplace, there's no guarantee its pressure and muzzle velocity listed will be the same as your rifle gets because your barrel's different as well as the components are from different lots and the neck tension is probably different. Barrels with oversize bore and groove dimensions will easily get 200 or so less fps with a given load; there's less resistance to the bullet entering and going down the bore to put pressure and velocity high enough.</p><p></p><p>It's normal to have as much as 100 fps difference between two people shooting the same rifle and ammo from a bench. Us humans don't hold rifles with the exact same force against our shoulders; the harder it's held the higher the muzzle velocity will be. Ammo factorys often use test barrels clamped in a solid, non-recoiling rest to test for pressure and velocity; they typically get higher velocities with the same ammo as consumers do with hand held rifles with barrels having the same internal dimensions.</p><p></p><p>IMR4350 or IMR4831 gave the best accuracy in the 7 RM in its competition heyday and I don't think it's any different today. And in standard SAAMI spec dimensioned chambers; no tight necks often believed to be best for accuracy. While slower powders typically shot the same bullet out faster, they didn't end up as close together on target down range. So one has to make a compromise deciding what's most important; bullet speed or bullet accuracy. And shoot at least 10 shots per group testing for accuracy; anything less ain't very indicative of what accuracy will be all the time.</p><p></p><p>For what its worth, when the 7mm Rem Mag was first used in 1000 yard matches back in the early 1970's, best accuracy happened with brand new cases or fired ones correctly full length sized back to virtual new case dimensions. The best ones for accuracy got only 800 to 900 rounds of sub MOA results at long range so fire forming cases took away a lot of that barrel life.</p></blockquote><p></p>
[QUOTE="Bart B, post: 655830, member: 5302"] First, the appearance, shape and other visible things on a fired case are typically a poor indicator of actual peak pressures developed. Most folks loading their own belted cases end up with pressures higher than SAAMI specs suggest. If ones load data matches what was published someplace, there's no guarantee its pressure and muzzle velocity listed will be the same as your rifle gets because your barrel's different as well as the components are from different lots and the neck tension is probably different. Barrels with oversize bore and groove dimensions will easily get 200 or so less fps with a given load; there's less resistance to the bullet entering and going down the bore to put pressure and velocity high enough. It's normal to have as much as 100 fps difference between two people shooting the same rifle and ammo from a bench. Us humans don't hold rifles with the exact same force against our shoulders; the harder it's held the higher the muzzle velocity will be. Ammo factorys often use test barrels clamped in a solid, non-recoiling rest to test for pressure and velocity; they typically get higher velocities with the same ammo as consumers do with hand held rifles with barrels having the same internal dimensions. IMR4350 or IMR4831 gave the best accuracy in the 7 RM in its competition heyday and I don't think it's any different today. And in standard SAAMI spec dimensioned chambers; no tight necks often believed to be best for accuracy. While slower powders typically shot the same bullet out faster, they didn't end up as close together on target down range. So one has to make a compromise deciding what's most important; bullet speed or bullet accuracy. And shoot at least 10 shots per group testing for accuracy; anything less ain't very indicative of what accuracy will be all the time. For what its worth, when the 7mm Rem Mag was first used in 1000 yard matches back in the early 1970's, best accuracy happened with brand new cases or fired ones correctly full length sized back to virtual new case dimensions. The best ones for accuracy got only 800 to 900 rounds of sub MOA results at long range so fire forming cases took away a lot of that barrel life. [/QUOTE]
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Reloading
Developing Load for 168 Berger New Brass vs Once Fired
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