New 20 Practical with new load development method.

[VarmintBob]

I use OBT method. These are the first 3 groups I shot with a .284 win using 140 gr TMKs and RL-16. The lowest ES is on the right. Which one would you pick? I think this took 15 shots start to finish.

 

[kpacker]

So, I guess the question is, does the method work? Since those book numbers use the same fixed variables.....I assume....., then does that hold water for the different powders? Or does it all go out the window once it's in a different gun and all those variables change? I'd be curious to know because it could eliminate need to try all kinds of powders and use up reloading resources to find a load
I get that the numbers will change once the variables change, but will the sensitivity ratio hold?

 

[Philward]

Less sensitive to what?

 

[Twellmann]

Played with all kinds of numbers like that when I got mine. It was my first wild cat. I really thought imr8208 was gonna be my answer. Turned out 25.8 gr of varget would consistently one hole all the 39-45 grainers. So I stuck with that. Don't recall any velocity numbers but I loved knowing if I could only see one eye peeking back through the bushes (predator hunting before thermals), I could punch that card. Have fun with your project!

 

[skipglo]

I can't tell from the Chrono pic what your gr weight was..it's cut off....but you show 2 test groups with 4895...the one with 25.7 grs. would support the Chrono...any chance you mixed them up ?

 

[Mike Matteson]

Following

 

[cb186]

24.9gr of N133, 39BK, .070" jump, 26" Wilson on a manual AR = 3880@80°, 5/8" 10 shot groups.

 

[JAYgs8163]

 

[Justice1327]

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

Yeah, I just don't know. I thought maybe I had a carbon ring but before I finish shooting it, I stuck the barre scope down it and it didn't. I double checked the overall length of the cartridge and it was within 2.260 so I don't know, but yeah, I'm definitely gonna try that again.

 

[Justice1327]

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.

Yes, I'm not for sure how it correlates or even has causation. Just something I'm trying that I read about but if you think about it, there are several powders that is recommended for a 308 with a certain size bullet likewise for a 300 win mag. And obviously the 6PPC pretty much LT 32 or N133 . Creedmoor family of cartridges with the right bullet weight is H4350.

 

[Justice1327]

So, I guess the question is, does the method work? Since those book numbers use the same fixed variables.....I assume....., then does that hold water for the different powders? Or does it all go out the window once it's in a different gun and all those variables change? I'd be curious to know because it could eliminate need to try all kinds of powders and use up reloading resources to find a load
I get that the numbers will change once the variables change, but will the sensitivity ratio hold?

That is what I'm gonna start trying next. I figured I would do three different size cartridges maybe four so I'll start with the 20 practical then do a 308 sized case maybe 30-06 but then try a seven mag or 300 win mag sized case.

 

[Justice1327]

I can't tell from the Chrono pic what your gr weight was..it's cut off....but you show 2 test groups with 4895...the one with 25.7 grs. would support the Chrono...any chance you mixed them up ?

No, they are two different size weight bullets. The top row with the Tite group is a 39 grain Sierra blitz King. Then the last row is with a 32 grain Vmax.

 

[Justice1327]

Less sensitive to what?

Powder, weight differences, I presume. Again I didn't invent this. This is just something I read by a very well-known Ballatician

 

[Justice1327]

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.
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That is awesome thank you very much