New 20 Practical with new load development method.

[Justice1327]

These are just some of the testing I'm doing with the 20 practical. Breaking in the brass and the barrel. Pretty happy overall. one thing I thought was strange was my best group had seriously high SD's.
I'm trying out a new method to figure out which powder works best. Using online data resources as well as reloading manual resources what I'm doing is essentially, taking the difference in the lowest and highest velocity and dividing it by the difference in the amount of grains between the lowest and highest charge weight. Example: Low vel 2200 , High vel 2500. 300fps Difference.
Load weight range : 25-30 gr with 5 being the difference. 300 divided by 5 is: 60. You do this for each loading for the powder that you want to check and you use the one with the lowest number. What this is supposed to be telling you is that the powder with the lowest number is the least sensitive . still have a few more powders to test out but so far it's doing well.
I'm also comparing this to efficiency rating in GRT and quick load

 

[Dmagna]

You lost me

 

[Justice1327]

You lost me

reloading manuals have 5 to 10 different powders. And they give a charge weight from low to high and then they give a velocity low to high . you take the highest velocity subtract the lowest velocity and you write that number down . then you take the highest charge weight minus the lowest charge weight and you write that number down. then take your first number of the velocity difference and divide it by the charge weight difference . The lower the number is supposed to mean that the powder is the least sensitive and should provide you with better, Precision and Accuracy. If you have several powders that you want to try out, this should give you an idea of which one would work best for that cartridge/bullet weight. Again this is from a book or data source and should give you a good starting point.
ideally, one should to try each of the powders they are interested in. By actually loading and shooting lowest charge weight and highest charge weight and annotate the velocity for each that way it is shooting in your rifle and you should have a more accurate number to determine which powder combois the least sensitive to changes.

 

[waspocrew]

Well if it works, it works…

 

[Teekerguy]

 

[Justice1327]

Tried to upload the spreadsheet, but it won't work. So I took a picture.

 

[Justice1327]

.

 

[7mm 08 fan]

I'd try that same 4895 load again for group size and sd , seems like your chrono might have hade a hiccup

 

[ncwg2boatguy]

I'd try that same 4895 load again for group size and sd , seems like your chrono might have hade a hiccup

Agree. Looks like chrono had a brain fart. It happens. 3 solid readings and 1 not even remotely close I would call a chrono error, not load error. Send that group again to be sure.

 

[John6]

FWIW, I use a stiff charge of H4895 in both of mine with very good results. I tried 5-6 different powders in my first gun before settling on 10X but tired of that stuff because of lot to lot variations. Good luck with your project.

John

 

[Mike6158]

Tried to upload the spreadsheet, but it won't work. So I took a picture.

I think you have to zip it to upload it.

 

[jepp2]

Since the 20P isn't well represented in the load manuals, some load development I did a few years back may be useful to you. I was trying to collect data and get a reasonable starting load based on my powder lots.

 

[iShoot17]

I am confused on how this calculated 'sensitivity' correlates to precision and accuracy.

If this were to be the case, wouldn't all manufacturers suggest using the same powder for each specific cartridge? And likewise - all handloaders be using the same powder / load for a given cartridge?

It seems many variables that may not be apples-to-apples (barrel length, temperature, etc.) are not being considered.

 

[BrentM]

I miss the days we could easily get powders to play with.

The method is interesting to me but my faith in the reloading data being consistent enough across the board is meh. Test Barrel length, test barrel design, brand of case, etc, a few variables that can scew the info. However, FPS change per grain is a good reference point to consider for wider powder nodes but is it that important with quality scales? Back in the day it was pretty common to get a base line and drop loads. Today your beam scale users are pretty much basement dwellers repeating my precious over and over with a pile of bench rest trophies surrounding the man dungeon.