Newb reloader here… Today was my first time out shooting rifle reloads which was a pretty cool experience seeing the results of different ammo recipes. An indoor range with 100 yard lanes opened up less than an hour away which offered a great venue to test the loads under ideal conditions. Based on published data I loaded up 8 different powder charges, 5 each, for a total of 40 rounds of testing. Consistent seating depth, case length, and full length sized. This was 308 Win ammunition loaded with 40.0, 40.5, 41.0, 41.5, 42.0, 42.5, 43.0, and 43.5 grains of IMR 4064. Once fired Federal brass and 168gr Sierra MatchKings. I shot some sighters with FGMM and then shot one of each charge ‘round robin style’ until all 40 shots were taken. It took about an hour and the mirage from my suppressor made seeing difficult at times.
Based on the targets, what do they tell you and what steps would you recommend taking next for fine tuning? For me, it appears 41.0 grains is right on the money - by my math that is a less than .50" group, five shots, factory barrel, and NOT the greatest shooter behind the rifle. I have a bullet and case comparator and planned to play with seating depth next.
FYI. Shooting equipment is a factory Remington 700 .308 Win. in heavy barrel, chopped and threaded to 20", Silencerco Harvester, McMillan stock, Jewell trigger, topped with a 5-22 Nightforce NXS. Reloading equipment is a Forster CoAx press and dies.
Looks like you have found an accuracy node somewhere between 40.5 and 41, and it looks like you are approaching another one at 43.5. You can go up to 44.5 (nosler book) with the 168’s.
If it was me I would work up loads from 40.3 up to 41.2 by 0.3 gr increments (3 rounds each). Going .2 under and .2 over your good loads from that initial test is a good idea.
Do the same from 43.3 up to 44.2 to see if there is another node in that range.
Once you zero in on your most accurate charge then you can play with seating depth, but remember, if this initial testing wasn’t done with the bullet seated into the lands then you need to be extremely careful when changing seating depth (seating into the lands) or else risk having a KABOOM.
Looks like you selected solid equipment, good on you.
edit
The above is if you want to continue load development and shoot at longer range. If you do continue do develop this load try testing the loads at longer range as it is hard to tell which 0.5 MOA group is better at 100 yards
If you only plan to shoot at relatively short ranges (for your rig) then just run with the 41.0 load, that is a fine group for a stock Rem barrel.
Sierra Matchkings can simply be loaded to mag length or Cartridge OAL spec. They’re not depth sensitive. And the leade on a factory REM barrel is usually pretty long… Mag length has always been great for all the 700s we’ve shot.
if that 41 gr load is repeatable I would say you are good to go. Might try to find a node somewhere around 42 to 42.5 for a little more velocity. With most of the .308 powders 42 to 42.5 gr is a go to load.
now you can always play around with different powders and bullets
Nice shooting! You’re done. I’d just stay at 41.0 gr IMR4064 for 168 SMKs, but I’d redo the ladder test with 175 SMKs instead.
That matches with the initial ladder testing I’ve done on an 18" OBR. But I started at 41.0 grs and went by 0.5 increments and worked my way up to 43.0 grs. My sweartheart load was at 41.5 grs of IMR4064 (1/2 MOA), haven’t gone to 0.2 increments around that range, but I load to 43.0 grs (3/4 MOA) to get some better transonic performance, even with reduced precision. I switched from 168 SMK to the 175 SMK for better transonic performance, as Bryan Litz and other SMEs recommend. In short, apparently there’s some gyroscopic instability that occurs at transitional velocity as the projectile approaches the speed of sound and goes subsonic, if I remember right, something technical due to the geometry of the boat tail and the drag divergence that occurs.
