Got something here that I haven't seen to this extent before (though I've loaded all my other guns closer to well established loads/lengths/milder pressures)...
New .243AI barrel (factory Tikka, rechambered by Kampfeld), first 10 rounds 48.5 to 52.5 H1000, getting moderately crunchy/compressed by the top end of that. Very mild pressure signs at the top. 2902 at the bottom, 3134 at the top. Lapua brass.
Fast forward 125 rounds or so, and I've had to back down to 48.0 to get 3063 (5 shot avg) and get pressure signs to go away (aside from very light ejector swipe).
Middle part of that 125 was 50 that I loaded at 51.5, and by the end was getting pressure signs (heavy bolt, heavy swipe) and seeing 3130 fps.
Have you needed to back off 4 grains from initial pressure, and gotten less velocity at pressure signs after speed up? I'm not unhappy with 3050ish, it's at or above what I was hoping for going into the project, but I've never seen barrel speed up follow quite this pattern before. Groups have been good but not incredible (0.9-1.25 moa 10 shot groups for most all charges) I saw close to 3100 with no pressure signs on my initial ladder though and thought there was a chance I'd end up 3100-3150 after speed up.
I've quit cleaning all my other guns, but they are all less overbore than this. Possible carbon ring? Are those real? Does the carbon ring stabilize? What say you, reloading experts? I've only been doing this for about 5 years, and always run 100+ rounds of factory ammo for break in/speed up so I've never done pressure ladder for the first shots through the gun. Was that my mistake?
New .243AI barrel (factory Tikka, rechambered by Kampfeld), first 10 rounds 48.5 to 52.5 H1000, getting moderately crunchy/compressed by the top end of that. Very mild pressure signs at the top. 2902 at the bottom, 3134 at the top. Lapua brass.
Fast forward 125 rounds or so, and I've had to back down to 48.0 to get 3063 (5 shot avg) and get pressure signs to go away (aside from very light ejector swipe).
Middle part of that 125 was 50 that I loaded at 51.5, and by the end was getting pressure signs (heavy bolt, heavy swipe) and seeing 3130 fps.
Have you needed to back off 4 grains from initial pressure, and gotten less velocity at pressure signs after speed up? I'm not unhappy with 3050ish, it's at or above what I was hoping for going into the project, but I've never seen barrel speed up follow quite this pattern before. Groups have been good but not incredible (0.9-1.25 moa 10 shot groups for most all charges) I saw close to 3100 with no pressure signs on my initial ladder though and thought there was a chance I'd end up 3100-3150 after speed up.
I've quit cleaning all my other guns, but they are all less overbore than this. Possible carbon ring? Are those real? Does the carbon ring stabilize? What say you, reloading experts? I've only been doing this for about 5 years, and always run 100+ rounds of factory ammo for break in/speed up so I've never done pressure ladder for the first shots through the gun. Was that my mistake?