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Hornady 123 ELD-M vs 123 Sierra MK and 8208
I have Criterion 18" barrel on AeroPrecision upper/lower combo. Typically shoot Hornady factory 123 Black just messing around, but like all things it's not on the shelves much.
January 2020, I loaded up some Sierra 120 MK and IMR 8208, using both Sierra and Hodgdon data, and my notes show I ran into pressure at the upper end of Hodgdon data. My notes from that session were sparse for the 26.5 to 27.4 that Sierra recommended, and I don't remember if it shot ok or not. Life started to get in the way, then covid hit and I stopped reloading.
Fast forward to late January '22, I loaded using Sierra's data for 8208/123 SMK, but instead I am using 123 gr Hornady ELD-Match, 2x fired Hornady brass pushed 4 or 5 thou back, CCI 450s, 2.250 COAL. Made 5 rounds each at 23.4, 24.6, 25.8, 26.9, and 27.5. We had nice weather today, I rushed setting up my LabRadar, and for the first 3 loads only picked up 2 or 3 shots of the 5, but finally got it lined up on the last two at 26.9 and 27.5, capturing 5 shots. My velocities at all levels very closely matched what the book predicted, but the top 27.5 gr load was 50 fps faster than book. I ran 2506 w/ SD 2.3 for 5 shots, book shows 2450. My 26.9 gr ran 2409 fps.
The thing is, Sierra's data says it's from a 24 inch barrel, and I'm matching the velocities w/ 18 inch barrel!! How different is the Hornady 123 ELDM from the Sierra 123 MK? Is the bearing surface that different? What am I missing?
The 26.9 gr was 1.2" ctc. The 27.5 load shot the best - around 3/4", had primers that look normal, 2 of the cases had sign of bolt unlocking a bit early (I've seen worse), and I prolly could tune the AGB to slow the unlock.
Temps today were 50 or 51 F. How temp stable is 8208? Will have issues when temps hit mid 80s?
Think I'll load 26.9 to 27.5 again, jumping a couple tenths at a time...weather will turn shitty again, so it'll be awhile before I get out.
I have Criterion 18" barrel on AeroPrecision upper/lower combo. Typically shoot Hornady factory 123 Black just messing around, but like all things it's not on the shelves much.
January 2020, I loaded up some Sierra 120 MK and IMR 8208, using both Sierra and Hodgdon data, and my notes show I ran into pressure at the upper end of Hodgdon data. My notes from that session were sparse for the 26.5 to 27.4 that Sierra recommended, and I don't remember if it shot ok or not. Life started to get in the way, then covid hit and I stopped reloading.
Fast forward to late January '22, I loaded using Sierra's data for 8208/123 SMK, but instead I am using 123 gr Hornady ELD-Match, 2x fired Hornady brass pushed 4 or 5 thou back, CCI 450s, 2.250 COAL. Made 5 rounds each at 23.4, 24.6, 25.8, 26.9, and 27.5. We had nice weather today, I rushed setting up my LabRadar, and for the first 3 loads only picked up 2 or 3 shots of the 5, but finally got it lined up on the last two at 26.9 and 27.5, capturing 5 shots. My velocities at all levels very closely matched what the book predicted, but the top 27.5 gr load was 50 fps faster than book. I ran 2506 w/ SD 2.3 for 5 shots, book shows 2450. My 26.9 gr ran 2409 fps.
The thing is, Sierra's data says it's from a 24 inch barrel, and I'm matching the velocities w/ 18 inch barrel!! How different is the Hornady 123 ELDM from the Sierra 123 MK? Is the bearing surface that different? What am I missing?
The 26.9 gr was 1.2" ctc. The 27.5 load shot the best - around 3/4", had primers that look normal, 2 of the cases had sign of bolt unlocking a bit early (I've seen worse), and I prolly could tune the AGB to slow the unlock.
Temps today were 50 or 51 F. How temp stable is 8208? Will have issues when temps hit mid 80s?
Think I'll load 26.9 to 27.5 again, jumping a couple tenths at a time...weather will turn shitty again, so it'll be awhile before I get out.
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