I just started into a new lot of imr-7828 so I chronographed a few loads with the new lot against the old lot as I always do when changing lots.I was surprised to see a velocity difference of 50fps.I added one grain to the charge and the result was almost identical velocity and accuracy with no pressure signs present.A similar situation occured a couple of months ago when I started usin the new h-1000extreme where the velocity difference was 60fps.How many of you actually check the velocity and accuracy when changing lots?

stubblejumper -- I chronograph 95% of all my shots, and this tells me exactly what you are talking about. Every lot change will show differences, some significant, others not. 7828, H-1000, RL-22, RL-25, etc being some of those I have worked with. In my unscientific opinion the slower the powder the more this shows up. I have started buying my powders I use most in the 5 to 8 pound amounts for this reason. I start less than max I normaly shoot for a particular powder, just in case the difference is significant. When I do find that same speed and accuracy I had with the old lot, it may be a grain or two grains to 1/2 grain different, generaly the smaller amounts. I take care to use the same type cases, primers etc. When I get back to where I started before the lot change, I now have enough powder in the new lot to work with for considerable time before I have to do the search again. ----------- I can see I was very blind before the chronograph, and didn't even know it. Good shooting.

[ 06-23-2003, 19:04: Message edited by: phurley ]

Changes is performance of powder from lot to lot is quite common.

As the other poster suggested, once you find a product you like, buying large batches of the same lot makes a lot of sense.

I commonly load up ammo with a new lot of powder and go to the range with the chronograph. I have observed some real changes from lot to lot.

A couple of the most glaring examples were with H 414 and XMR 2015. It was years ago, but a change in lots of H 414 one time caused a change in velocity in my 6mm Remington of around 150 fps. More recently, a change in lots of XMR 2015 caused a velocity drop of 250 fps in my .223 Remington and over a 100 fps in my 7mmTCU!!

Fortunately, both these changes were such that they caused lower pressures and velocities. Had they been changes in burning rate in the other direction and had I not worked up my loads again I most likely would have had a real problem!

Changes in performance of 50 fps is common and is of little consequence.

R F