Accuracy issues with a custom 338 Laupa

[Korhil78]

That is a good group with the 89.5. Load the two best ones that you got (88.5&89.5) and shoot them out a little farther and see what they do. Try 400-500 if you can but don't go under 300 yards.

For the future (and this is just my opinion and how I do it), start with one powder, one bullet etc and test it out. If you don't find what you like, try a different powder. The reason I told you to go with the H1000 and 300 gr Bergers is because just about everyone can find a good load with that combo.

Another thing is that you are shooting way to much during load testing which will hurt your accuracy. Shooting for accuracy is pretty dang strenuous and will fatigue you. This will hurt your accuracy and can also help you develop bad habits while fatigued such as slapping the trigger etc. Break up your shooting sessions. Shoot 4 loads (3 rounds per load) one day and then come back and shoot 4 loads another day.

If you are already doing this then just tell me where to go. Just giving you what I do.

 

[RockZ]

My 338 Lapua AI loves Retumbo, so,I'll have to suggest starting with that.
You can use whatever powder you want..the process is the same!

I think the problem is that you are not doing a proper seating depth test. Your max difference is only .030"
That would be my First change not max.

Try loading 3 rounds of retumbo at 90,91,92,93 grains at .010" off the lands and shoot them through the chrono.
Pick the load with the tightest velocity spread. Looking for extreme spread of10fps or less.,... Don't worry about the group size in this step.

If one powder gives horrible velocity spreads....try your next favorite powder.
It's the powder and charge that you fine tune for tight vertical at long range.

You use seating depth to dial in the group . Now let's get that done!

Load 3 each at the powder charge that gave the tightest extreme spread.

Start at .010" off the lands then:
.040,.070,.100..120.

At 100yds...Shoot only 2 of each., that way you can really concentrate, the third is in case you pull a shot.
You should find a group that shoots the best....should put two in one hole.
That's your load.

If you feel good...shoot that third shot in your one hole group.
Save the others for fouling loads.

 

[RockZ]

I forgot to mention in the seating depth test if I don't get close to a one hole group in the first test I keep splitting the difference in the two best consecutive seating depths until I get the desired results.
I just bring a portable lee press to the range and do it there.
I load all rounds at .010 off the lands and seat them deeper .030 and shoot them right there at the range. That way I don't waste rounds or load up a bunch and have to pull bullets later.
Plus I can shoot an extra round at any given depth to confirm the results.