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Rifles, Reloading, Optics, Equipment
Gunsmithing
FN action: BOLT THRUST REDUCTION
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<blockquote data-quote="fj40mojo" data-source="post: 506988" data-attributes="member: 19129"><p>FYI, nobody "desired" 3100fps, I just stated that it might be attainable or approachable with the Ackleyized Swede. BTW I'm getting 2850 with 45.5grns of H4831, Lapua brass, Fed primers, and Hornady 140g SST from a 26" barrel, that is <strong>1.5 grains<the published max load for this powder in Nosler #6 Manual.</strong> Hardly what I would call "hot rodding". Their test barrel was 23" and gave 2663fps with 45.0g, oh and yes it goes there accurately-3/8"@100yards. I'm not advocating that we all "hot rod" our rifles, but this example illustrates how different two rifles can be. <strong>By all means, practice safe reloading techniques, always approach max charge weights with caution, know how to recognize pressure signs,</strong> but on the same token know your cartridge/action history too and realize that factory ammo and reload data may not reflect actual cartridge potential and just because it's the newest uber magnum doesn't mean it's better. Funny that you mentioned the host of new 6.5/.264 cartridges, I'd say this was all done well over 100 years ago and that Rem and Lapua have reinvented the wheel. If these velocities (2800-2850) are safe in .260 (53g H2O) and 6.5x47L (49g H2O), why would they not be safe in the same action chambered for the larger volume 6.5x55 Swede (58g H2O)? I don't know how many grains of H2O you gain by going to the BJAI but it stands to reason that any gain would increase volume and thereby cartridge potential and in concert with the reduced bolt thrust, well sounds like a win win situation to me. Those darn Swedes were on to something and so was Ackley. Don't know if you've noticed but the Swede has a lot of body taper a common trait in military cartridges, but by blowing most of the taper out of the body of the case more pressure is exerted against the walls of the chamber and less rearwards into the bolt face reducing bolt thrust. This is because as pressure is exerted outwards against the walls of the case the tapered walls of the chamber act like a wedge redirecting forces and squeezing the case rearward into the bolt face. Less taper equals less bolt thrust. This and moving the shoulder forward and out to 40 degrees increases case volume. How much, I don't know, can't find it published anywhere. Is it enough to get to the next accuracy node beyond 2850fps? I don't know, I don't own one, wish I did. Just sayin.<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite11" alt=":rolleyes:" title="Roll Eyes :rolleyes:" loading="lazy" data-shortname=":rolleyes:" /> Sorry for hijacking your thread Bigstrap.</p></blockquote><p></p>
[QUOTE="fj40mojo, post: 506988, member: 19129"] FYI, nobody "desired" 3100fps, I just stated that it might be attainable or approachable with the Ackleyized Swede. BTW I'm getting 2850 with 45.5grns of H4831, Lapua brass, Fed primers, and Hornady 140g SST from a 26" barrel, that is [B]1.5 grains<the published max load for this powder in Nosler #6 Manual.[/B] Hardly what I would call "hot rodding". Their test barrel was 23" and gave 2663fps with 45.0g, oh and yes it goes there accurately-3/8"@100yards. I'm not advocating that we all "hot rod" our rifles, but this example illustrates how different two rifles can be. [B]By all means, practice safe reloading techniques, always approach max charge weights with caution, know how to recognize pressure signs,[/B] but on the same token know your cartridge/action history too and realize that factory ammo and reload data may not reflect actual cartridge potential and just because it's the newest uber magnum doesn't mean it's better. Funny that you mentioned the host of new 6.5/.264 cartridges, I'd say this was all done well over 100 years ago and that Rem and Lapua have reinvented the wheel. If these velocities (2800-2850) are safe in .260 (53g H2O) and 6.5x47L (49g H2O), why would they not be safe in the same action chambered for the larger volume 6.5x55 Swede (58g H2O)? I don't know how many grains of H2O you gain by going to the BJAI but it stands to reason that any gain would increase volume and thereby cartridge potential and in concert with the reduced bolt thrust, well sounds like a win win situation to me. Those darn Swedes were on to something and so was Ackley. Don't know if you've noticed but the Swede has a lot of body taper a common trait in military cartridges, but by blowing most of the taper out of the body of the case more pressure is exerted against the walls of the chamber and less rearwards into the bolt face reducing bolt thrust. This is because as pressure is exerted outwards against the walls of the case the tapered walls of the chamber act like a wedge redirecting forces and squeezing the case rearward into the bolt face. Less taper equals less bolt thrust. This and moving the shoulder forward and out to 40 degrees increases case volume. How much, I don't know, can't find it published anywhere. Is it enough to get to the next accuracy node beyond 2850fps? I don't know, I don't own one, wish I did. Just sayin.:rolleyes: Sorry for hijacking your thread Bigstrap. [/QUOTE]
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FN action: BOLT THRUST REDUCTION
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