Load Development and Barrel Speed Up

[DavidMarlow]

Forgive the stupid question but stupid questions are what I do best....

When going through the load development process, looking for what your rifle likes, does barrel speed-up affect that, or does it strictly affect the velocity? Right now, I'm just practicing fundamentals with factory ammo at 100 yards while simultaneously creating once-fired brass. Should I keep doing that while watching chronograph data, or is it okay to start working up loads within the first hundred rounds?

 

[spife7980]

I would shoot all your factory ammo, clean the barrel and then begin load development with one big lot of matching brass.
It may break in with 5 shots, it may take 150, no one knows. If you start now it’ll be fine but I find it easier to keep everything at the same point in the process.

 

[diggler1833]

I am pretty guilty of starting load development with less than 50 rounds down the pipe.


Yes the barrel will usually speed up. However, I can't remember in at least the last 4-5 barrels where that additional speed led to groups coming apart.

 

[Doom]

I sort of surprised we are all kinda thinking along the same lines. The data you may receive by working up during break-in is not going to be wasted. It may not be the final load but it will lead you to the final load.

After a reasonable number of rounds you can start load development. I would do so after a couple of boxes of factory ammo. I bought 40 rounds of PMC 308 for that purpose and I still have about 10 rounds lying around. For normal shooting less than 600 yds any small changes should not affect the tuning and if it does its normally only a small change, not a new work up.

If I were taking the rifle to a major competition I would be more diligent because shooting at distances of 600 yds or greater I not only want the load to be accurate but I don't want another factor (velocity changes during the competition) to affect the point of impact. But I would still work up during the "break in".

It also depends to some extent on what you are trying to achieve. If pushing for maximum velocity the accuracy "nodes" tend to be narrower than slower loads and move sensitive to velocity changes.