Accuracy node vs. charge

F

fat but funky

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Hi Guys,

So, I've been trying to work up loads for my 30-06. Have tried 180 gn Hornady SST's and Sierra Pro-hunters, as well as 150 gn Hornady Interbonds and Nosler Accubonds.

I noticed that both 150's had their best accuracy at roughly the same charge (i.e. +/- 0.1 grain). Similarly, both 180's had best accuracy at the same charge - although in absolute terms the Pro-Hunter was way better than the SST.

While I suppose this makes sense, it still struck me as quite a coincidence. Jacket construction, ogive geometry, boat tails, etc all varied across bullets

I've never seen this before - then again it has never taken me this long to get an adequate load before either.

So I'm wondering if other guys have seen this?

Thanks

Fat
 
If the same change weight gives the same velocity, then yes the nodes will be the same because the barrel time will be the same.

If I'm creating a load for a weight of bullet that I have previously worked an OCW load for, I will just tune the load to the same velocity, which is often at the same charge weight.

This isn't always obvious when you're using powders that aren't temperature stable and developing loads at different times of the season, at different temperatures. If velocity changes, it means that pressure and barrel time have also changed. They have to, they're directly related to one another. If your load is off because temperature has changed drastically, you can generally adjust your charge weight to get the velocity you originally tuned it to and it will group again.

If you don't already have one, get a chronograph. That is just one of it's uses.
 
That's interesting. I have seen with the 30-06 and 308 with the same brass, identical velocity, and with the same bullet huge differences in accuracy depending on what powder was used. Recently with the 30-06 running loads at 2700 fps (18 inch bbl) the differences in group sizes between varget, RL15, and IMR 4895 were quite dramatic. Also in my 308, with varget, cci 200s, and 150 grain accubonds i notice a huge difference in accuracy between RP brass and WLR brass. Velocities are averaging 2730 fps give or take a few fps and accuracy averages 1.45 in with RP brass and 0.70 inch for the WW brass. I need nearly 1 gr of varget in the WLR brass to match the RP brass.
 
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