I have an old Ruger M77 MK2 Target/Varmint with a 1:9" twist 26" semi heavy barrel. It is pared with a Vortex Viper PST 4-16x50mm FFP scope. A few years back, I worked up a nice pet load, consisting of a Hornady 105 gr A-Max over 42.6 gr RL19 for 2817 FPS. With this load, I am able to shoot about a 5/8" five shot group at 100 yards, and I am quite happy with that.
Recently, I aquired some 103 gr ELD-X bullets, as Hordany discontinued the 105gr A-Max. Hornady lists the 103 gr ELD-X with a G1 Ballistic Ceofficient of 0.512. My old A-Max was .500. Yesterday, I put 10 of the new 103 gr ELD-X bullets over a charge of 42.6 gr of RL19, and loaded them to the same OAL as the old A-Max. I shot (2) "groups" that measured roughly 8". I could not believe my eyes, so I shot a group with my old A-Max load. That group was satisfactoy sub MOA.
What the hell? Is the new bullet to long for my 1:9 twist bbl? Do I have to start all over back at square 1 with load development? Does anyone have any wisdom, advice, or thoughts to share with me? I was hoping this new bullet would be a direct replacement, and I could just load up 200 more rounds.
Recently, I aquired some 103 gr ELD-X bullets, as Hordany discontinued the 105gr A-Max. Hornady lists the 103 gr ELD-X with a G1 Ballistic Ceofficient of 0.512. My old A-Max was .500. Yesterday, I put 10 of the new 103 gr ELD-X bullets over a charge of 42.6 gr of RL19, and loaded them to the same OAL as the old A-Max. I shot (2) "groups" that measured roughly 8". I could not believe my eyes, so I shot a group with my old A-Max load. That group was satisfactoy sub MOA.
What the hell? Is the new bullet to long for my 1:9 twist bbl? Do I have to start all over back at square 1 with load development? Does anyone have any wisdom, advice, or thoughts to share with me? I was hoping this new bullet would be a direct replacement, and I could just load up 200 more rounds.
