ES/SD During Initial Load Development

[Tiny Tim]

Was doing a seating depth test with 215 Target Hybrids in a 300 Rum. 0.015, 0.040, .045, 0.60 off lands. 80 gr H1000.Federal 215 GMM in virgin ADG brass. No prep, loaded and shot. Just fire forming before load development. ES 17/SD6 @0.015. Avg 2776 fps. Each increase in depth resulted in 16 fps, 10 fps, &10 fps reduction in velocity respectively. ES/SD became 37-50 fps and SD 12-22 fps. 0.045 resulted in .5 moa. All others hovered around 1 moa.i find the numbers confusing. Is it possible I randomly loanded on a velocity node when .015 off. Seems odd that ES should change so drastically across the board if not. I will likely test .015 and .045 in a ladder later. 1 moa with low ES/SD is better than .5 moa with terrible ES/SD at distance. Sorry to ramble. Any advice?

 

[Rick Richard]

I would test with once or twice fired brass before making any conclusion. Just my experience.

 

[RegionRat]

Tim, my guess is your un-prepped brass will leave an open question that nobody can guess what will happen next if you try again with your fully prepped brass.

Your recipe may be sensitive to neck tension or it may turn out you never get it to your goals.

My advice it that if you care about performance, and for the cost of each bullet, I would fully prep and understand the difference between virgin brass and fired brass. YMMV

 

[Jud96]

Sounds like by adjusting seating depth you took yourself out of a node. Find what seating depth shoots best then bump your powder up to get your velocity back to where it was before. If 0.045 shot the best, then do an OCW test and find your best powder charge. You should be north of 3000fps with a 215 Hybrid in a .300 RUM.

 

[BALLISTICJESUS]

Is this with a new barrel / rifle? Or rifle with under 50 rounds fired through it?

 

[Tiny Tim]

I would test with once or twice fired brass before making any conclusion. Just my experience.

Agreed. Just seemed abit odd. Was fire forming Lapua 234 Brass to 243AI. That's alot of brass movement. 36 shots gave ES of 18 and SD of 5. Was just out shooting so decided to set the chronograph up just to see what was happening. Can get alot done in this colder weather. Trying to make the most of it.

 

[Tiny Tim]

Is this with a new barrel / rifle? Or rifle with under 50 rounds fired through it?

Barrel has about 150 rounds