Originally posted by Josh Haker
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Leverevolution
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Reading primers at Grendel pressures is extraordinarily challenging.
Really flat primers suggest pressures that are on the order of 10,000 psi or more over the ~52,00 SAAMI max pressure for the Grendel.
This article was written to explore the question, but the bottom line I got from it is that most of us do not have the intuition to read primers well enough for the technique to be a "go to" first choice: http://shootersnotes.com/articles/wh...ures-too-high/shootersnotes.com
"To those who have fought and almost died for it, freedom has a flavor the protected will never know."
-- Author Unknown
"If at first you do succeed, try not to look astonished!" -- Milton Berle
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Thanks JASmith, that's a good article. I've been struggling to find a reliable indication for the pressure of a load. I see ejector marks on light loads, and flattened primers show up after the pressure is already 10K over max. So far my grendel has broken 3 bolts in about 15,000 rounds. I have to think that my loads were over pressure for that to happen. I've been left with measuring the case head diameter over a several reloads. That doesn't help much during load development so I end up going with a conservative load and then proofing it to make sure it is really safe. My pet peeve is that the loading data, even from manufacturers, has loads that have turned out to be too hot in my rifle. For example, Hogdgon shows a max load of 28.5 for a Sierra HPBT and 8208 XBR. I broke a bolt with 27.8 gr of 8208 gr of XBR and in retrospect my primers were showing some pressure signs. Another example is the Lapua reloading guide showing a max load of 27.8gr of N133 with a 108 scenar. I can't get anywhere near that load in my rifle and suspect that 26.3 gr of N133 is over max. Where are these numbers coming from?
How many of you have been shooting loads that give above average muzzle velocities for at least 10,000 rounds without ever breaking a bolt?
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SAAMI indicates that one should use 4% of the expected mean pressure as the standard deviation when developing loads for commercial use. My own experience to date with a single chamber with about ten different loads with published pressures suggests that the standard is reasonable.
This disccussion is one attempt to translate their standard into terms understandable by more people: http://shootersnotes.com/articles/saami-pressure/. I have been told, however, that more work needs to be done to make it easily understood by even half if the Grendel community,
This variability is one of the reasons Bill Alexander suggests we load to 50ksi when the SAAMI max average operating pressure is about 52ksi. That practice gives margin to help avoid bolt breakage while not costing much in downrange performance.shootersnotes.com
"To those who have fought and almost died for it, freedom has a flavor the protected will never know."
-- Author Unknown
"If at first you do succeed, try not to look astonished!" -- Milton Berle
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That's half of what I'm used to paying-haven't seen prices this low in a long time.NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com
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Originally posted by biodsl View PostFor anyone using LEVERevolution, Widener's has it at $14.50 a pound right now.
https://www.wideners.com/reloading-s...e/rifle-powder"One Good Shot Is All I Need."
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Originally posted by 6.5 Grendel View PostLOL its $44 a pound to ship ummm no thanks.
Last time I bought powder, I set up a group buy locally to spread out the cost of the hazmat and shipping. Brought in 50# of powder, and 50k primers IIRC. Split the shipping and Hazmat 6 ways then it's manageable.Sticks
Catchy sig line here.
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