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?

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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.
 
That's pretty fast for a 20 inch barrel. Most shooters that I know and shoot with are using 30 inch barrels to launch 155 gr bullets at around 3000 fps. However I don't know of any of them using ball powder. Most are sticking with Varget, N140 or N150.
 
Maynard is on point. Local gunsmith in my area shoots FClass with them bad boys and told me if I wasn’t gonna run 30” I better stick to above 168grains and hope for good wind. I shoot out to 1100 in PRS with both a 20” and 22” R700 in 308. I’ve only ever shot Sierra and Varget. The Ginex Primers were no bueno in the detailed PMC Brass we use. We switched to a Winchester primer and the velocity jumped immediately. Most guys are running ELDMs or ATips so availability on those will be sparse in comparison.
What exactly are you trying to achieve that has you pushing Mach speeds?
 
rubberdonuts said:
Maynard is on point. Local gunsmith in my area shoots FClass with them bad boys and told me if I wasn’t gonna run 30” I better stick to above 168grains and hope for good wind. I shoot out to 1100 in PRS with both a 20” and 22” R700 in 308. I’ve only ever shot Sierra and Varget. The Ginex Primers were no bueno in the detailed PMC Brass we use. We switched to a Winchester primer and the velocity jumped immediately. Most guys are running ELDMs or ATips so availability on those will be sparse in comparison.
What exactly are you trying to achieve that has you pushing Mach speeds?
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Moreso than anything else, I wanted to see what it was capable of doing. Definitely backing off that last load. 2700-2800fps is plenty fast out of a 20in barrel imo.
 
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I don't mind loading some a bit hotter for my initial ladder tests with a new bullet/powder combo, for a new gun anyway. I can unload them if I see something I don't like before getting to them, the load you have there may be somewhat OK in cold weather, but, I wouldn't use it.. The one case there with the ejector imprint tells me to back off a bit, the primers say pockets probably won't last long, so, back it off to somewhere around that #12 shot and see if you like how it shoots or not.
 
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