I am back from the range with stuff to report on RL-15.5 in the 338-06 and the 9.3x62.
About the rifles - both are JES rebored 1903 Springfields. The 9.3 has about a 23.5" barrel and the 338 is 19" long. With previous loads, the 9.3 has been extremely accurate but the .338 has not yet shot well for me. Both rifles have Leupold M8 fixed 4X scopes, a tiny compact on the 9.3, and a full sized on the .338. Both rifles have long throats and the bullets are loaded to 3.375" for magazine length. Lapua brass for the 9.3, necked up FC 30-06 for the .338. All primers are CCI 200.
My velocity goals for the 9.3 match the good data Mule Deer has published for 60K PSI-ish pressures, and for the 338-06, I am looking for about 100 FPS less than the Hornady max data show due to the 4.5" shorter barrel.
That means ~2650 FPS for the 250AB and just under 2500 for the 286 PT (today I used the 250AB and a no-name 285RN for testing. I bought a few big bags from some guy that got them from an estate. They look just like PPU 285 or Lapua Mega 285).
For the 338-06 I'm looking for 2400' for the Hornady 250RN and 2600 for the 225 SP. I shot both those bullets today.
I loaded two rounds each for three charges each to get in the ballpark. Below I will try to summarize the results but the formatting might get goofy when I post it. I list the two speeds and the center-to-center distance between the two rounds.
9.3x62, 250 NAB (goal = 2650')
60 grains - 2421, 2454, 0.27"
61 grains - 2511, 2494, 0.45"
62 grains - 2542, 2547, 0.20"
Summary - looks like outstanding accuracy potential, and room for 1.5 to 2.0 grains more powder to reach the goal.
9.3x62, No-Name 285RN (goal = 2500')
58 grains - 2290, 2266, 0.46"
59 grains - 2312, 2314, N/A, the first round hit just off my paper - it was just about 2"
60 grains - 2368, 2358, 0.95"
Summary - looks like at least 2 more grains needed to reach the speed goal.
338-06, 250 Hor RN (goal = 2400')
50 grains - 2233, 2230, 1.00"
51 grains - 2292, 2266, 2.23"
52 grains - 2330, 2322, 1.70"
Summary - maybe another 1.5 grains to reach 2400', accuracy potential not exciting (but it is certainly minute-of-moose, and about as good as this rifle has ever shot before)
338-06, 225 Hor SP Interlock (goal = 2600')
54 grains - 2504, 2489, 0.47"
55 grains - 2549, 2530, 1.06"
56 grains - 2594, 2589, No kidding one hole. Barely perceptible elongation - can't measure it.
Summary - Excellent! I hit my speed goal of ~2600' and the accuracy potential looks good. Very excited to repeat the 56 grain charge with more rounds. These 6 rounds formed a cluster much smaller than the average 3-shot group this rifle has delivered with previous loads.
I hope these results will help others develop their own loads with RL-15.5. Please post your results. Don't forget my rifles have long throats and are loaded to magazine length. I will sneak up closer to the velocity goals next Wednesday and report back. Will also try the 210 NPT in the 338-06 and see if it plays well with RL15.5. I really hope so but can be happy forever with the 225 Hor SP if it keeps up what it did today.
Cheers,
Rex
