Eye opening experience

So I finally had the opportunity to go try out some of my rifle loads for a couple of Mil-Surp rifles. A Yugo M48 Mauser, and a Mosin-Nagant 91/30. The Mauser performed relatively well, but I found a couple of loads that seemed to be more accurate. I'll be focusing on those loads to find which one is more accurate.

The real eye-opener came when I tried the loads I'd worked up for the MN. I know rifles can be particular about what loads they prefer. But I was a bit miffed when my first load printed a softball sized group at 25 yards, and considerably high and to the left. Like 6 inches high and to the left. I'm thinking to myself, "Stupid Russian piece of garbage." I tried to adjust the front sight a little bit, and it FELL OFF!!!

Now I was really miffed. I put the sight back on, adjusted it as best I could, and it was still printing high and to the left, but not as severely. I figured I'd just keep shooting the loads I'd worked up, to at least get the velocities. Then came a surprise. When I got to the mid-range load, the groups tightened up surprisingly, and were coming much closer to point of aim. And then came the sweet spot. Got up to about 2600fps, and it's now hitting at point of aim, and the groups are amazingly tight. Got it up to 2700 fps, and suddenly this rifle is a tack driver!!!! Granted, it was only at 25 yards, but I put 7 rounds into a hole the size of a quarter!

So now I'm gonna work up some loads around the two that were so accurate and see if i can find this rifle's favorite load.

To those requesting the loads that this gun was happy with, here ya go.

Sierra 150gn soft point (.311")
CCI250 primers
51.6 and 52.6 grains of Accurate 4350
seated at 2.850"

51.6 avg mv ~2580fps
52.6 avg mv ~2750fps

So a bit of follow up. Went back out yesterday, same rifles. Slightly different loads, hoping to find out if it was a fluke or if the rifle was really that accurate.

Let's just say I need to slug the bore on this beast and find out what's wrong. Because about half my shots were high and left, the other half dead center.... Regardless of load. And this was on a bench, at 25 yards. Some shots were as far as 6 inches high and 6 inches left.

On a positive note, I did figure out the load that my Yugo M48 likes.

150gr Hornady SP (0.323")
CCI 250 primer
47.0 grains of Accurate 2015 (which, by the way, is a max load)

Group of 0.807 inches at 25 yards with iron sights. Get rid of a quasi-flyer and the group shrinks to 0.691 inches.

Now, just for fun, guess which one of these cases was from a near minimum load, a mid range load, and the max load? (including an unfired one for comparison)



EDIT:

Well, I just slugged the bore on the 91/30. and it's .313 groove to groove, .303 land to land. So the .311 bullets I'm using should be just about perfect.... Anyone know the twist rate for the 91/30 off the top of their heads? Maybe too light of a bullet? (Sierra 150gr SP)

Well, it's a 1:9.5 twist rate...

Which means that's not the problem either, as the minimum for the loads I'm using is 14.5.......