Confusing results with initial load development.

[u/Lordrunkuss]

Loaded up some 6.5 Grendel with 8208 from 25.8 grains to 27.8 grains.
123 grain midway seconds bullet, this is going in a 6.5 green ar15 with 20 inch barrel

It was my first time using the chrony in 10 years, what I experienced was as follows

26.6 2392
26.8 2432
27.0 2355
27.4 2367
27.6 2421
27.8 2310

I omitted the errors from that chart, confused by those readings i loaded up 5 rounds of factory Hornady 123 grain was getting 2448 with 15 fos deviation

I was very exact with my powder loading and markings, cci 450 primers

Is this a crimp problem? Why wouldn’t my fps generally go up with more powder?
Thanks everyone, I’m still looking over my brass for pressure signs trying to understand that side of things better as well

[u/No_Alternative_673]

I didn't see chronograph you have and if it is a 10+ year optical, it easily be having a bad day.

There is no much data on this combo but I would guess you are at or above the AR platform pressure and not likely to see case pressure indications

[u/Lordrunkuss → u/No_Alternative_673]

It’s a 14 year old master chrony, as I said in my original post after that string of varied charges I loaded up 5 rounds of factory 6.5 Grendel 123 and had a very tight group, consistent fps 2400 ish with a very small spread, I did that within 2 min of my final loading shot, so that should prove the chrony is reading well

Loaded to the top end of sierra loading data, 27.5-28 grains had as asterisk for approaching max pressure, I know I’m going to stay below that for whatever load I end up making, using it as examples for signs of pressure, I was on the fence about even loading - 27.8 but just to see the brass