Tuning N133

[Tim Singleton]

Ok, share some wisdom.
I've read a lot on the subject and watched Jack Nearys youtube videos several times. I still have questions.
I've read to be careful when you shoot a screamer group because the next one will fall a part.
Well that happened to me at Riverbend I had a great group best I had shot in a while. The first relay in the HV class. So it was right after lunch temps were climbing fast. The next relay was a whopping .32 and the next wasn't much better.
I've read Gene Beggs posts on dropping charge weight as temp goes up. But I throw with a Harrel measure so as the temp goes up the powder expands so your supposed to increase the volume to account for the powder expansion

How do you do both? Drop the charge and increase volume with any kind of accuracy.
Do you just take a couple different loads to the line each time?

 

[Boyd Allen]

Have you ever thought of setting aside a day to work at the range, when there is going to be weather like that match had? You could load under shade, right there, and note what your in tune load was (by volume and weight if you want) at different times of the day as well as what the temperature was. Just a thought. Personally, I have not seen much to concern me about powder bulking up. What I usually have to deal with In warm weather, is it drying out in the measure, combined with the increase in temperature, both causing the load to go out of tune on the high side. Recently, I tuned up mid morning, and as the day got hotter and drier (under 30%) I saw the load pick up some vertical, so I dropped it some, by volume, and got a dot. In that case, since I had been looking at some other things about my shooting, and had let it get to over a bullet hole of vertical, I think that I dropped as much as .6 (six detents on a my Harrell, but I don't remember for sure. (All this with 133)

 

[Tim Singleton]

Have you ever thought of setting aside a day to work at the range, when there is going to be weather like that match had? You could load under shade, right there, and note what your in tune load was (by volume and weight if you want) at different times of the day as well as what the temperature was. Just a thought. Personally, I have not seen much to concern me about powder bulking up. What I usually have to deal with In warm weather, is it drying out in the measure, combined with the increase in temperature, both causing the load to go out of tune on the high side. Recently, I tuned up mid morning, and as the day got hotter and drier (under 30%) I saw the load pick up some vertical, so I dropped it some, by volume, and got a dot. In that case, since I had been looking at some other things about my shooting, and had let it get to over a bullet hole of vertical, I think that I dropped as much as .6 (six detents on a my Harrell, but I don't remember for sure. (All this with 133)

I have, I've gotten a box rigged up to put my scale in. Just haven't had a chance to use it yet.
That's good feed back, kind of what I was wondering if allowing for the change in powder expansion was not as critical as dropping the charge weight as temp increases.

 

[SGJennings]

Jack Neary says: "We throw by volume but we shoot by weight".

My first suggestion would be to throw by weight, to use a ChargeMaster on a battery pack, but that might be a problem.

Second, would be to separate the variables and determine them in isolation before putting them together. For example,

1. Using weighed charges, use a spreadsheet to plot how velocity changes with respect to change in your powder charge at a fixed temperature.
2. Using weighed charges, on a separate page in the spreadsheet, plot how velocity changes with rising temperature at a fixed powder charge.
3. Use your Harrell's or whatever dispenser to plot how thrown charges vary through the day with respect to temperature, humidity, density altitude (depending on your thoughts on that matter).

Terry, I think that you've seen part of this in my spreadsheet for the 220 Beggs. I'd be happy to talk you through how to do this. It's not hard, but it is a bit tedious.

Greg Jennings