Not a new gun, but out of mothballs for the first time in a while...
I've always admired it's uncanny ability to put any off-the-shelf match ammo into sub 1" groups. So long ago I just settled on a handload (with 168gr Sierra Match Kings) that I picked off the chart to duplicate factory match ammo. It shot well (3/4" groups) and I was happy.
Well two years ago I got a Chrony, and so I though it about time to really work up a load for this rifle, so antsi and I headed to the range on Friday.
I looked at Hodgdon's and Sierra's online data and compared it to my Sierra 3rd edition manual. Hodgdon was the least conservative of the three and the top load showed compression with 45.9gr of IMR 4064.
I decided not to go to compression and started at 39.8gr of IMR 4064, loaded one round at 0.3 gr increments up to 44.9gr, which was just to the level of the top of the shoulder. I loaded 18 rounds plus two more in the middle for fowlers.
Using a dummy cartridge I set my bullets out to ~0.015" off the lands, which ended up at 2.900" - 0.100" longer than the COL listed for this bullet in all the data. The Savage chamber seems to be long enough for 190gr and maybe 200gr SMK's. Since I would be loading them one at a time, I didn't worry about the limited neck tension - 2.800" is the correct COL if you want full neck tension.
I used three separate targets and divided the rounds into three sets of six, spreading adjacent loads onto separate targets in an effort to see more clearly where each individual bullet hit the target, instead of having bullets passing through the same hole.
I also color coded the ogive of each bullet with a Sharpie, so that if there was a question as to which hole was which, the color code might help out... well I'm 90% confident that I labelled all the holes correctly. My son wrote down the velocities from the chrony and I called the shots, which he also wrote down.
The resulting groups answered the "uncanny" question. The rifle with a limited amount of input from its shooter put 18 bullets - each with a different powder charge - a into a 1.20" composite group (all three targets). Only four shots did not fit completely inside a quarter. Those four were completely outside the quarter. Not counting those four, the overall group size was 0.64".
As for velocity the lowest charges were just under or just above 2500fps from a 20" barrel. The top three loads hovered around 2770fps. Comparing this to the Hodgdon data, it's probably best that I stopped at 44.9gr of powder, since the top load is listed at 2766fps from a 24" barrel. As for pressure signs, there were none to the fired cases, as the top loads mic'ed at the exact dimension as the lowest loads, primers were not flattened, but the top three loaded exibited the very faintest sign of cratering on the primer. For future loads I will not go past 44.0gr of powder, and I'm satisfied with the IMR 4064, which is right about the sweet spot for .308. Incidentally, the max load from Sierra is 43.4gr in the new data and 44.7gr in the old 3rd Edition. If I do try another powder in the future it will be H4895 or Varget.
Analysing the data and the bullet holes revealed something very interesting...
The charge weights I had been using (trying to duplicate match factory match ammo velocity) yielded one of the the largest group sizes - right at 3/4" - right where this rifle has been shooting since it was new. The largest group size goes to shots #6,7,8 at 0.95".
Loads #3,4,5 - 40.4gr, 40.7gr, and 41.0gr - were grouped together in a 0.18" group (velocity was 2498 to 2534fps), notably lower than the 42.5 to 43.5gr charges I had used previously (2682 to 2715fps). Shots #10, 11, 12, and 13 formed the second worst group of the bunch, but 13, 14, and 15 settled down again, with only a 0.030" vertical spread and 0.46" center to center horizontally.
The moral to the story is that I will be focused on two places - 40.7gr for a target load at ~2530fps, and 43.7gr when I load up 165gr BTHP Sierra Game Kings for a hunting load at ~2725fps - one I doubt I will ever use in this heavy rifle.
I've always admired it's uncanny ability to put any off-the-shelf match ammo into sub 1" groups. So long ago I just settled on a handload (with 168gr Sierra Match Kings) that I picked off the chart to duplicate factory match ammo. It shot well (3/4" groups) and I was happy.
Well two years ago I got a Chrony, and so I though it about time to really work up a load for this rifle, so antsi and I headed to the range on Friday.
I looked at Hodgdon's and Sierra's online data and compared it to my Sierra 3rd edition manual. Hodgdon was the least conservative of the three and the top load showed compression with 45.9gr of IMR 4064.
I decided not to go to compression and started at 39.8gr of IMR 4064, loaded one round at 0.3 gr increments up to 44.9gr, which was just to the level of the top of the shoulder. I loaded 18 rounds plus two more in the middle for fowlers.
Using a dummy cartridge I set my bullets out to ~0.015" off the lands, which ended up at 2.900" - 0.100" longer than the COL listed for this bullet in all the data. The Savage chamber seems to be long enough for 190gr and maybe 200gr SMK's. Since I would be loading them one at a time, I didn't worry about the limited neck tension - 2.800" is the correct COL if you want full neck tension.
I used three separate targets and divided the rounds into three sets of six, spreading adjacent loads onto separate targets in an effort to see more clearly where each individual bullet hit the target, instead of having bullets passing through the same hole.
I also color coded the ogive of each bullet with a Sharpie, so that if there was a question as to which hole was which, the color code might help out... well I'm 90% confident that I labelled all the holes correctly. My son wrote down the velocities from the chrony and I called the shots, which he also wrote down.
The resulting groups answered the "uncanny" question. The rifle with a limited amount of input from its shooter put 18 bullets - each with a different powder charge - a into a 1.20" composite group (all three targets). Only four shots did not fit completely inside a quarter. Those four were completely outside the quarter. Not counting those four, the overall group size was 0.64".
As for velocity the lowest charges were just under or just above 2500fps from a 20" barrel. The top three loads hovered around 2770fps. Comparing this to the Hodgdon data, it's probably best that I stopped at 44.9gr of powder, since the top load is listed at 2766fps from a 24" barrel. As for pressure signs, there were none to the fired cases, as the top loads mic'ed at the exact dimension as the lowest loads, primers were not flattened, but the top three loaded exibited the very faintest sign of cratering on the primer. For future loads I will not go past 44.0gr of powder, and I'm satisfied with the IMR 4064, which is right about the sweet spot for .308. Incidentally, the max load from Sierra is 43.4gr in the new data and 44.7gr in the old 3rd Edition. If I do try another powder in the future it will be H4895 or Varget.
Analysing the data and the bullet holes revealed something very interesting...
The charge weights I had been using (trying to duplicate match factory match ammo velocity) yielded one of the the largest group sizes - right at 3/4" - right where this rifle has been shooting since it was new. The largest group size goes to shots #6,7,8 at 0.95".
Loads #3,4,5 - 40.4gr, 40.7gr, and 41.0gr - were grouped together in a 0.18" group (velocity was 2498 to 2534fps), notably lower than the 42.5 to 43.5gr charges I had used previously (2682 to 2715fps). Shots #10, 11, 12, and 13 formed the second worst group of the bunch, but 13, 14, and 15 settled down again, with only a 0.030" vertical spread and 0.46" center to center horizontally.
The moral to the story is that I will be focused on two places - 40.7gr for a target load at ~2530fps, and 43.7gr when I load up 165gr BTHP Sierra Game Kings for a hunting load at ~2725fps - one I doubt I will ever use in this heavy rifle.
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Thanks for sharing
