Generall load developement vs. velocity question

[Road_Clam]

I spent the afternoon testing and logging various .308 168 smk and 178 a-max rounds and also got chrono #'s. I have a box stock rem 700 Varmint with a 26" barrel and a 12 twist. Overall it seems as my rifle likes 168's the best and keeping the Velocity between 2500-2600 . In contrast I read so much internet load data of guys obtaining their best factory rifle accuaracy with upwards of 2700-2900 ? My data seems to indicate that past 2700 my accuracy starts to falls off. Right now as a new hand loader I am loading all my rounds light. Does this situation seem abnormal ? Not too worried about this, I am simply going to absorb my collected data and move foreward with what I observe. Maybe my rifle simply likes a lower velocity..

 

[dmoran]

ES (Extreme Spreads) can tell us where the best accuracy is between loads.

As to velocity zones, sure one zone can be predominately more accurate. But typically not in as large of scale as your referring to.
Example:
At 2620 to 2640 the accuracy was good
Then again at 2690 t0 2710
And again at 2755 to 2775

Just my 2-cents
Donovan

 

[amlevin]

Accuracy and speed is going to be all about the barrel. The first accuracy node revealed during a load workup is the lowest speed. As you increase loads you might uncover another node that isn't as good as the first but consider this.

As charge weights increase so does recoil. A lower recoil as a result of a light load "forgives" a lot of issues with one's shooting position or "gun handling". Add recoil and these issues can be magnified. There are times you need the extra speed, especially if trying to reach out to extreme ranges for the round/caliber.

If one finds an accuracy node at higher charge weights where the groups have shrunk somewhat over the groups on either side of that charge weight, but it's not as tight as the light charge, work on gun handling skills. One of my rifles has three clear accuracy nodes. One down in the low 2400 fps range, another in the mid 2500 fps range, and a third one right at 2700 fps range (.308 with 175 gr SMK). When shooting in the "third node" it's imperative to have an almost flawless position. I shoot with rear beanbag and bipod and the added recoil exploits every little indiscretion. A lot easier to get small groups with light loads but a lot harder to reach out beyond 1k.

 

[watercam]

There are accuracy 'nodes' for both velocity and seating length (and action screw tension if you want to get into that as well). Shoot a ladder test (one round of each charge weight - .2-.3 grain increments from starting load to something close to maximum) with which ever bullet you choose. Do this at 200-300 yards if possible so that you will see a vertical string of shots. Some will be closer to each other than others. Draw a diagram of each shot as you shoot so as to keep track of which was which charge. At the points where you have tighter clusters of shots, go back a shoot test groups of those charges. Once you find a load you like, start playing with seating depth in .010" increments from touching the lands out to .040" off the lands (or further).
You needed an excuse to go to the range more, load development is a good one!

 

[Road_Clam]

Thanks for all the input ! Appreciate the knowledge !

 

[amlevin]

There are accuracy 'nodes' for both velocity and seating length (and action screw tension if you want to get into that as well). Shoot a ladder test (one round of each charge weight - .2-.3 grain increments from starting load to something close to maximum) with which ever bullet you choose. Do this at 200-300 yards if possible so that you will see a vertical string of shots. Some will be closer to each other than others. Draw a diagram of each shot as you shoot so as to keep track of which was which charge. At the points where you have tighter clusters of shots, go back a shoot test groups of those charges. Once you find a load you like, start playing with seating depth in .010" increments from touching the lands out to .040" off the lands (or further).
You needed an excuse to go to the range more, load development is a good one!

You mean Dan Newberry's OCW method? Dan suggests load increments of 1% rather than a fixed "number".

BTW, once you do the OCW test, then optimize the selected charge weight with seating depth, you can then go back to charge weight adjustment for a super-fine tune due to the different effective case volumes.