Tweaking a freebore, is runout more critical and any other advice

[thethirdpig]

I have a trg-s in 30-378. I have been trying to develop an accurate hunting load as opposed to benchrest. If I could get 1" groups at 100 yds consistently I would be satisfied. After much experimenting with different powders and bullets I have found the most accurate load is 105.2 gr of Retumbo behind a Swift 180 gr Scirrocco seated to the max. length allowed by the mag. Though this combination is the best shooter, thus far, I will invariably still get a flier that goes off always horizontally and sometimes with some vertical. I have tried powder charges in 1/10th increments above and below 105.2 and these open up the group size. I wonder if runout could be a factor in the "invariable flier". I do not have a guage to measure this but if I need to invest in one I may or perhaps a heavier bullet would perform better. All opinions are welcome.

 

[ballistictip2506]

I would doubt very much the issue is runout although who am I to say. What I do see as a problem is the statement you made that 1/10 grain powder graduations begin to open up your groups and/or cause flyers. If this is truly the case then you most definitely are not in the OCW sweet spot. Initial load testing should deal primarily with POI not group size. I think you need to re-visit your charge weights with a different approach. (OCW Overview - Dan Newberry's OCW Load Development System ).
Hope this helps .

 

[rscott5028]

Runout could be one of many issues.

A horizontal flier would likely not be resolved using the OCW method.

What is your barrel profile, length, and twist?

Do you have a brake?

If you allow ample cooling time?

Do you get good 2 or 3 shot groups?

If 2 or 3 shots are always tight and the 3rd/4th are fliers, then it's a function of heat/stress in the barrel/action. ...and/or the shooter due to recoil.

If the flier occurs any time, then it may be runout or just not a good load for this rifle.

You also need a good scope with solid mounting and properly adjusted to remove paralax.

...plus 100 other possibilities

-- richard