05-16-2020, 07:15 PM
P_ham86,
i've not encountered that with APPV yet. not sure what to make of it.
a caution, though, on increasing pressure. the barrel extension which the bolt lugs lock into isn't as substantial as the receiver bolt lug abutments that bolt actions lock into. though you're not getting any catastrophic failure, which just means that the heat treat on the barrel extension was done correctly, as you continue to stress this interface above what it was designed to sustain, i suspect one risk is that the bolt lugs will begin go bend/crack at their root and that the extension abutments will also start to bend a little.
if you have a way to measure headspace accurately, please do keep a close eye on this parameter as you pursue your upper end loads. usually headspace will start increasing prior to onset of catastrophic failure. once the chamber pressure is high enough to start to bend parts, as shows up as increasing headspace, both the bolt and the barrel extension need to be scrapped and replaced.
since the SAAMI MAP spec for the 6.5 Grendel is 52K psi (not CUP!) your primers will likely not show any classic pressure signs until you're well above SAAMI MAP levels. at which point the forces on the barrel extension lug abutments and the bolt lugs are above their design limits for long term sustainability i would presume. due to the larger case head area as compared to the 223 case, for any given comparable chamber pressure, the force on the Grendel bolt lugs and barrel extension will be greater. force = pressure x area. so for the same force, the chamber pressure in the Grendel needs to be lower than the 223. and this will reduce the classic pressure sign on primers.
as others have said, if you need a 6.5-300 Weatherby, buy one. you shouldn't try and turn the Grendel into something it isn't. hopefully you don't take this as an insult. not meant that way. just suggesting caution so your rifle will run, safely, a long time, and you never have to deal with a ka-boom.
-tdbru
i've not encountered that with APPV yet. not sure what to make of it.
a caution, though, on increasing pressure. the barrel extension which the bolt lugs lock into isn't as substantial as the receiver bolt lug abutments that bolt actions lock into. though you're not getting any catastrophic failure, which just means that the heat treat on the barrel extension was done correctly, as you continue to stress this interface above what it was designed to sustain, i suspect one risk is that the bolt lugs will begin go bend/crack at their root and that the extension abutments will also start to bend a little.
if you have a way to measure headspace accurately, please do keep a close eye on this parameter as you pursue your upper end loads. usually headspace will start increasing prior to onset of catastrophic failure. once the chamber pressure is high enough to start to bend parts, as shows up as increasing headspace, both the bolt and the barrel extension need to be scrapped and replaced.
since the SAAMI MAP spec for the 6.5 Grendel is 52K psi (not CUP!) your primers will likely not show any classic pressure signs until you're well above SAAMI MAP levels. at which point the forces on the barrel extension lug abutments and the bolt lugs are above their design limits for long term sustainability i would presume. due to the larger case head area as compared to the 223 case, for any given comparable chamber pressure, the force on the Grendel bolt lugs and barrel extension will be greater. force = pressure x area. so for the same force, the chamber pressure in the Grendel needs to be lower than the 223. and this will reduce the classic pressure sign on primers.
as others have said, if you need a 6.5-300 Weatherby, buy one. you shouldn't try and turn the Grendel into something it isn't. hopefully you don't take this as an insult. not meant that way. just suggesting caution so your rifle will run, safely, a long time, and you never have to deal with a ka-boom.
-tdbru