Load testing with non-fire formed or fire formed cases.

[phillh]

Hi all,

Are there any significant velocity differences between load testing fire formed and non-fire formed cases, with the same powder load? 308 cal 2206H & ADI cases.

I ask because I am fire forming for a new barrel and load testing at the same time. Am I wasting my time, and should I just test with fire formed cases?

I imagine it will give me a base line, but I would think that fire formed cases will be more consistent in velocities.

Would I expect the velocities to be faster or slower in fire formed cases?

Thanks in advance for the responses and sorry if it has already been covered in another post.

Cheers, Phill.

[Rich4]

Probably slower as you are wasting energy expanding the case, however it depends on the cases fit, also how many cases do you have to fire form?
If it’s a large batch go ahead and retweak on the 2nd go around.

[Weairy]

Generally found from new brass to fireform there’s maybe 0.1gn of powder or 0.005 seating depth change required to fine tune in the 308. My 223 however shoots the same load for fireform or virgin brass, zero difference in grouping.

[Tim L]

I have found that my 308 barrels go through a velocity change at the 250 to 300 round mark.
Given I put 300 cases with a barrel this kind of dictates what's required.
I will do load testing and find a seating depth that works and shoot all 300 cases. Then I revist load testing knowing I'm pretty close.
I have found nearly every barrel I've run has had a velocity increase at that 250-300 mark. So it's generally back off half a grain or so and check seating depth. I don't know if folks find this happens running 155s, but it's what I've experienced with 200+

Just another comment on fireforming. I've seen many people just throw bullets in the dirt because they are "just fire forming".
This is a waisted opportunity.
All trigger time should be good, quality, trigger time. Even if the gun isn't accurate, every trigger pull should be a practice shot. Centering the group is an invaluable skill.
Don't waste the opportunity.

[dazza284]

Well according to that tread mythology of load development I don't think anything matters just get a teaspoon and shove some propellant in a case and seat a pill and have at it . .

Yes I know not helpful.

[Weairy]

I don't know if folks find this happens running 155s, but it's what I've experienced with 200+

We find it’s around 300-400 rounds with 155.5s in the Kreiger barrels, but definitely a thing