pajasonc Wrote:those pictures at 1800 are not showing much expansion. The 2000 fps one showed good expansion.
Which basically means that a 14.5 " grendel using the 123 sst is good out to 300, where you can expect the bullet would look like the picture with decent espansion. Any further and there is a very real chance that you won't get a quick clean kill. So to take the 14.5 " further you would either need to boost speed(handload hotter) or use a softer bullet(which at close range runs the risk of over expanding and not penetrating enough) I would like to see how much the amax's expand at 1600 fps.
One mistake I used to make was imagining the bullet pushing through the tissue in the shape that we see represented by different recovered projectiles from gel.
After watching high-speed photography of gel shots, I started to see that the things are spinning at very high RPM, and that they maintain a lot of that RPM in the tissue.
For Grendel using 1/7.5" twist, you're at 240,000 RPM. I had a talk with Hornady's engineers about this at SHOT, and they said that they notice a repeatable result of higher RPM causing more wound cavity effects than a slower twist.
In Volume II, we have a table showing barrel length effective hunting range and point blank range with barrels from 10.5" to 24" using the 123gr SST.
14.5" at 2350fps will expand out to at least 325yds, if not 350yds.
14.5" at 2420fps will expand out to 360-400yds with 123gr SST.
For those that are worried about getting expansion at these distances, I would use the 129gr ABLR and toss those concerns. Most people hunting with an SBR are doing so in pretty tight terrain and vegetation.
If anyone has questions about their expansion thresholds, chrono your rifle and record the temps so you can enter those into your ballistics program.
For those without access to a chronograph, keeping it 300yds and in is sound logic with a 14.5" Grendel and factory 123gr SST if you are counting on expansion for your intended on-target results, especially in the cold.
NRA Basic, Pistol, Rifle, Shotgun, RSO
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6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
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