What happened with my jump in velocity ?

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g3arhead

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So I’m reloading 308, Winchester Staball match, federal case , Ginex LR magnum primer, SMK 150 bullets. 2.750 COAL. Basic ladder test. Went from 48.8 grains to 49.2. Check out my velocities. Shot 10-12 was 48.8 grains. 13-15 is 49.2.

No heavy bolt lift. Do I have big pressure signs?

IMG_3665.jpegIMG_3666.png
 
There's definitely an ejector pin divet on the case on the right and its primer is flatter than the others. Ball powders can generate pressure quite quickly especially when compressed. I would back off. How much higher than published data are you velocity wise?
 
savagelh said:
There's definitely an ejector pin divet on the case on the right and its primer is flatter than the others. Ball powders can generate pressure quite quickly especially when compressed. I would back off. How much higher than published data are you velocity wise?
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No published data from Sierra. Only data is from Hodgdon and only data is available for Sierra 155 SMK loaded to 2.775 COAL. Max for that is 48.7c.

Load data is based off 24in barrel. I’ve got a Tikka T3 with a 20in.

Max for that book data based on the 155gn is 2898fps.
 
In my experience Federal brass is a touch softer than Winchester, Lapua etc… and it tells you a story about too much pressure a bit quicker (that indentation IS an indicator).
Bolt lift becoming stiff means you’ve DEFINITELY gone too far. Be happy with a wee bit less velocity instead of needlessly pushing it to the limits and dancing on the edge of safety. Always wear glasses, when something ruptures you may get a face full of high pressure gas resulting in a bloody mess. I’ve seen it, reloaders become much more ‘conservative’ after such an incident.
 
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