I need some advice. I'm attempting to work up a load for a Tikka CTR in 6.5 Creedmoor. I'm using Hornady brass, Hornady ELD-x 143 grain bullets, H4350 powder and CCI primers (have tried both standard and magnum). It seems that whenever I get to an acceptable group size (for me that is 1/2 moa), my velocity extreme spread/ SD gets bigger. When I get my velocity / SD number reduced , my groups open up (sometimes over 1 moa). I've tried adjusting seating depth, powder charge and primers and it doesn't seem to help much. Any advice anyone can give me as to what to try next would be appreciated.

Targets don't lie.

Take the load further out.

Good luck.

Primers make a difference is group size. Like said as, you increased the load your groups got smaller. Work on up higher looking for pressure signs as you go. I'm shooting the 140's in my AR with the 6.5 CM. I'm averaging 1 moa or less at 300 yrds.

You may want to get o hold of some better brass, Lapua. It will make a difference in group size.

Changing one variable at a time is the optimal way to ensure you are isolating problems. SD/ES is a measure of consistency not of accuracy.

Another issue that is overlooked and very important - Neck tension. Related to this will be work hardening which will require annealing to rectify.

Distance will be the verifier of all efforts. A group that looks good at 100yds, may open up at distance or be too slow to buck the wind.

Reloading is a practice in the "Law of Diminishing Returns". You can chase variables till your exhausted. Then you throw the brass or barrel away and start over.

Andrew

You don't give us any data to work with. Charge weight, velocity, ES and SD would give us an idea where you are. You should use a method to determine the ideal charge weight. Either Ladder test or Optimum Charge Weight (Dan Newberry - Google).


RMD

IMO, vel spread isn't a huge deal but for maybe shooting past 600. Try diff primers, not a fan of mag primers but they can be better or worse for accuracy.
When I get a good load for any rifle, I run a series & just swap primers. Sometimes it helps with accuracy & vel dev.

Fro smallest deviations, you will likely want to sort brass by internal volume & number of times fired.

Get some Lapua brass.

How much neck tension are You using?