Chrono results continued

[JCSC]

The attached two string of 5 shots each are representative of two identical ladders for the 140 bthp / H4350 and using lapua and hornady brass.

I have to say I was figuring on lower chrono #s than what I got. Both of these 25 round ladders had decent groups. Anywhere from 1.25 - .6 5 shots. I was also surprised that one brand of brass shot faster across the board than the other.

what will make the most significant improvements in these numbers, considering that I have sounds practices in place already?

My SD ranges from 9-20 and ES as high as 52.

 

[Blue68f100]

The Lapua is giving you lower SD across the board, shows the brass is more consistent. When it comes to low SD a lot of things come into play. Neck tension, bullet runout, the accuracy of the powder load, and Primer. I've got the best all around improvement use the Fed Gold Metal Match primers.

Your load is slower than mine, but I'm using a AR-10 with a 24" barrel, 2725 fps @ 75F.

 

[JCSC]

The old beat up hornady brass is 75 FPS faster as well. I had 5 factory 140’s and they ran about 2600 with the box showing 2700. I guess that’s just the difference in barrel length.

 

[lordpaxman]

The attached two string of 5 shots each are representative of two identical ladders for the 140 bthp / H4350 and using lapua and hornady brass.

My eyes aren’t what they used to be but it looks like there was a difference in primers for the two strings? I’ve seen slight variations in velocity for primers, but not a lot. Most likely your internal volume is different between the two case types.
Are you trying to find an accuracy or velocity node? I would do that first, then adjust the jump to lands and make sure your groups are what you want at the distance you want. To drop the SD further, consistency in everything is required. It could be you’re at the floor in which case a different bullet may be necessary, like a Berger. Good luck.

 

[JCSC]

You are correct in the primer difference. LRP and SRP.

honestly, I don’t know what I am doing. I now own a chrono and I am collecting data on the normal OCW methods I run.

also checking some of my proven loads to see how the chrono numbers look.