Changing Powder Lots

[Clint Tyler]

I have ran out of powder that I have been shooting out of my .300 win and bought some new. It is the same IMR4350 but a new lot how do you guys load for new powder lots? Do you start over from scratch or do you fine tune from the load before? I shoot 180 gr accubonds over 70gr of IMR 4350 I was thinking of loading up 68.8gr, 70.0 gr, and 70.2gr and see where I am at. Is moving up in that small of incriments in a .300 going to do any good or will it be too minute to tell.

Thanks

 

[Shortmagman]

I use RL-19 for a number of applications so I buy it in 5 lbs containers. I just started a new lot, I dropped down a couple of grains and worked up one grain at at time until I was at where my old lot had been. I shot them over my chronograph along with rounds from the old batch. What I found in two different guns was it will take about one extra grain of powder to produce the same velocity as the old powder. With the new lot being slower than the old one is was not dangerous. But if they were in reverse(old lot being slower) I could have run into some pressure problem.


I think that you are on the right track, but I would load 68, 69, 69.5, 70.0, and 70.5. Of course you need to shoot them across a chronograph to see how they compare with your old batch.

 

[EZShooter]

I may be off base, but in my experience making minute changes in powder charge doesnt do much unless you are at or near max charge (when loading for 30 caliber magnum cartridges) - what I am looking for is a powder that gets me to max pressure at close to a 100% load density. I have had better results when I have correlated those two factors - density and being close to max pressure, than if I make .2 grain or 2 grain changes (with the exception that once I get close to max, the changes are very small, say .2 or .3 grains). Directly responding to your question - most manuals I read state to load 5% below max charge weight whenever you change a single component, i.e. lots of powder, so I would think you need to go down by 3 or 4 grains and work your way up to be safe. If your primers are a different brand or lot, rework back up, if you have a different lot of powder, rework the load. The only thing I havent done is rework the load if I am using the same bullet, but from a different box... I may be overthinking this, but hey, better to be safe than sorry I say.