Reducing Standard Deviation

[jugi16]

Hello guys and gals.

Thought I'd pick some peoples brains here and see what some of the more knowledgeable people have to say on setting up a good load for their rifles.

I recently got my rifle built by Henry Rempel in .308 on a factory rem 700 action. I can't say enough good things about this guy the rifle shoots the lights out with everything I put in it.

At the moment I am using Varget and in the 42.6-44.0 grains area 175 SMK Lapua brass and BR2 Primers MV is 2680-2750 respectively. My SD is running in the 7-18 area. Is this as good as I will get? There doesn't really seem to be any difference in accuracy in any load. It's shoots .5 inch at 100 yards all day. I am trying to get my ideal load to shoot out to 1000 yards. This is my first time using a chrono and monitoring stats on my loads.

Just curious what everyone else does to set up loads for their longrange guns. One more thing my concentricity is in the .001-.003 range. Should I be neck turning Lapua brass? I use redding comp neck bushing dies and just give my necks a 3/4 neck .002 squeeze.


Thanks all happy shooting.

 

[CyaN1de]

Sounds like you are doing everything right so far.

If you have the equipment, cleaning the necks up to 80% (or thereabouts) shouldn't hurt anything.

.001-.003 is acceptable runout for match loads. I save the lesser runouts for the longer ranges....just incase.

I have also indexed my .003 loads so they go into the chamber the same way by putting a felt mark on the case at the highest or lowest point when measuring the runout.

Typically you want your SD to be under 10 at the very least...if you can get below 5 then your running a stellar load for long range.

I did a 15 round test the other day with my 6BR and had a ES of 14 fps and an SD of 4 needless to say I was quite happy considering it has had 1000 rounds through it since the last time it was chronied when I was working up a load for it.

 

[Ganderite]

You want your SD to be under10.

One variable to play with is neck tension. I suggest you remove the decapping rod and neck expander so to necksize to the max and have max neck tension. try 10 this way and 10 the usual and compare.

Also, if you want to shoot at longer range then grouping at 100 means almost nothing. I shoot at a patch at 300 or 4 patches at 500 when short range testing.

 

[jugi16]

So it seems as if I should just chuck my chrony. I have been talking to a few people and they say the same thing. High ES High SD but they shoot great groups at 300 and 500 yards. Thanks all for all your help.

 

[Ganderite]

A big SD (say, 35) won't affect the group much at short range. If youa re only shooting at 500 yards, the shoot your groups at 500 and pick what works.

If you want a good 1000 yard load, shoot your groups at short range, so there are not to many atmospheric variables to mix up the results. As i said before, I shoot my groups at 300 or 500, depending on the weather and what range is available.

For long range you want a load that groups well AND has a low SD (under 10).

And 100 yard shooting is a waste of time unless you are tryng to deblop a 100 yard load. It does not translate to long range performance, where things like barrel harmonics become important.