Benchmark and LT-32 in my 220 Beggs

[GSPV]

Here is one-half of a velocity map for Benchmark and LT-32 in my 220 Beggs. You might have to blow it up some to see it. If anyone wants the raw Excel file, just PM me.

It shows velocity for 4 loads at 0.3 grain increments at competitive velocities. I did 3 shots at each 0.3 grain increment. I plotted the average velocity for each increment and did a linear regression to show how velocity varies. The "scaled" versions at the bottom tell the story pretty plainly. You can see the slope of the line and the R^2 value in the right side of those charts. The slow shows you how velocity grows per tenth of a grain. R^2 is the coefficient of determination which, waving my hands a bit (a lot), is a percentage confidence.



PS: Thanks Sam! It is good to work with a PhD radiochemist.

 

[GSPV]

Re: Benchmark and LT-32 in my 220 Beggs + N133

This is old, but just wanted to add some "quick start" info.

I'm shooting a 220 Beggs. Lapua brass. 53 grain bullets. 205M primers. I'm finding my best with light neck tension, jammed a hair into the lands. From what I gather, this will work with a 22 PPC short as well.

These are at 66 degrees F.

Benchmark: 25.6 25.9 26.2 26.5 26.8
3286 3344 3364 3382 3442
A regression on this yields 11.7 fps per 0.1 grain of powder.


LT-32: 25.0 25.3 25.6 25.9 26.2
3437 3446 3531 3551 3575
A regression on this yields 12.7 fps per 0.1 grain of powder.

(Sorry, this one is hectic. I was trying to quickly find the competitive range)
V-133: 25.7 26.0 26.5 26.7 27.1
3443 3465 3543 3551 3579
The regression here yields 10.4 fps per 0.1 grain of powder.
I don't feel as good about this one. I only had one shot per charge. I was in a hurry. Will do more later.

You should be able to use this and the standard 30 fps per 5 degrees of temp change to stay in tune. Drop me a line and let me know what you find.