Help me understand the data from my reloads

So up front I know my rifle is inherently not the most accurate out there. Factory plastic stock, not floated or bedded in any way (not really possible for this one), factory trigger and decent glass with a sporter barrel (its a model 111 in 308).

That being said, it seems like every powder charge produces the same results (w/in reason). I wanted to find a bullet my rifle likes more so I am trying out Sierra Game King in 150gr. I am using it in used brass, CCI primers, and various charges of Varget. Cases are all w/in .002" of each other in length and COL is the same variance according to my cheapo Cabelas digital calipers. Bullets were seated .020" OTL.

I tried from 38.5 to 40.5 grains of Varget in 0.5 grain increments and in four shot groups they had no noticeable trend.

All at 100 yards on a somewhat breezy day:

38.5gr - 1.32"
39.0gr - 1.24"
39.5gr - 0.93"
40.0gr - 1.60"
40.5gr - 1.43"

Seems that it dips down at 39.5 but I could have just gotten lucky. It was on an old beat up sled at the range to take out as much human factor as possible but it had no straps.

So overall less than ideal situation but I tried to control as many variables as possible. Even still it seems that there isn't much conclusive data. I had hoped to take the "best" powder charge and then work on the jump to the lands and find the best there, but I really don't think I have enough data to go on.

Thoughts?

Looks to me that 39.5gr is the one it likes. Load it up again and see if you can get repeat grouping. If so then I would play with the seating distance on that load. Have you shot many Factory loads out of the rifle to see what the hand loads are being compared to. I would think over a .25" difference would be the "sweet spot" for me I would start tweaking from there. But the breezy day would have cramped my style for load development day.

You might try using the load with the smallest vertical spread then see if you can shrink the horizontal spread with the seating depth.

I would continue working up to at least 42 or 43grs. I bet there is another node in the higher region you haven't hit yet, but from what you've posted the 39.5 looks like a good spot to work from.

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Originally Posted by tufrthnails

Looks to me that 39.5gr is the one it likes. Load it up again and see if you can get repeat grouping. If so then I would play with the seating distance on that load. Have you shot many Factory loads out of the rifle to see what the hand loads are being compared to. I would think over a .25" difference would be the "sweet spot" for me I would start tweaking from there. But the breezy day would have cramped my style for load development day.

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This rifle will consistently shoot 1.5 moa with normal core-lokt remington 150. I agree about the breezy day, but I gotta take what I can get with my work schedule.

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Originally Posted by JTCrl

You might try using the load with the smallest vertical spread then see if you can shrink the horizontal spread with the seating depth.

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Good point! That would probably eliminate *SOME* of the effect from the wind. If thats the case it seems that the highest load is best (40.5). I think I'll just have to keep loading them up a bit higher to see how much tighter it gets.

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Originally Posted by LoneWolf

I would continue working up to at least 42 or 43grs. I bet there is another node in the higher region you haven't hit yet, but from what you've posted the 39.5 looks like a good spot to work from.

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I'll try that out and see how much tighter it gets the next time I get to the range. Hopefully the wind will be calmer this weekend!

I'd suggest hanging with 39.5 and varying the COL to see if you can discern a difference. And, before you get off of the 39.5 charge, just for the heck of it, change primers and run a few rounds with 39.5, the best COL, and just a different primer.

Tufrthnails has the right idea. You must be able to duplicate results in order for results to be valid. Try loading six of each charge weight or bullet seating depth setting. Then shoot 3-shot groups on one target and the second set of three on a new target and compare. If you can duplicate accuracy you're on the right track...... I also like LoneWolf's input. All the good .308 loads I've ever had were in the range he suggests using Varget and your bullet weight. Keep us posted :)

I would load a set of bullets .2 of a grain above and below 39.5 to see if there is a sweeter spot. After that I would start in on the seating depth. I would also suggest that you contact Sierra, they might be able to tell you what seating depth their bullets work best.

Even at 40.5 you are way below the books hottest load. Are you getting any sooting on the case after firing? With a .308 and a 150 grain bullet you go up to 44 grains or so but look for pressure signs. I would work up in small increments till you find another node where the gun will shoot tighter yet.