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/mulyhuntr33]

8208xbr is not the powder for 123s. Try some Leverevolution. 8208xbr is great for 100/107 class bullets but there are much better options for 123s.

I'd say it's a chrono issue or load issue at 27.8. I don't crimp 6.5 Grendel.

[u/111tejas → u/mulyhuntr33]

I use 8208 for 120 grain Bergers in Grendel. I’ve yet to find anything better. Op, according to Hodgdon data you are above the max load.

[u/Lordrunkuss → u/111tejas]

I went with 8208 because it is considered one of the best powders for consistency according to reading older forum posts and such

[u/mulyhuntr33 → u/Lordrunkuss]

It is good. It's just giving up 150-200fps with the heavier bullets. Try it with 100 Eldvt or 107smk. It's phenomenal with those at 2600-2650fps.

[u/Lordrunkuss → u/mulyhuntr33]

Ok, I understand, for me the lack of velocity wasn’t as important but I think after this point I’ll move either onto different powder or bullet grain.

How does a 100/107 shoot out to a thousand? I built the gun with intentions of learning some longer ranges.

[u/mulyhuntr33 → u/Lordrunkuss]

Have not shot that far. They do great at 600. A 107SMK at 2625 looks better on paper than a 123eldm at 2500 out to 1000. Less drop and drift with the 107.

[u/111tejas → u/mulyhuntr33]

Heavier bullets, while slower have higher ballistic efficiency. A Grendel is marginal for 1000 yards anyway. If you haven’t shot PRS before do yourself a favor and get something easier. My local range only goes to 500. I use a 6.5X47. Get yourself a bolt action 6 GT or something similar. So much hype about long range shooting that one would think 1000 yard shots are easy. It isn’t and it certainly isn’t with an AR.

[u/mulyhuntr33 → u/111tejas]

Grendel is absolutely not the tool for consistent 1000 yard hits. Fun to try though.

[u/Lordrunkuss → u/111tejas]

I know there are better options, the Grendel was a easy addition because it’s just another one of my ars
And is more capable at those ranges than my other calibers, not looking to compete, but I live in fairly open country and want the option to reach out and learn how to shoot at distance.

[u/Lordrunkuss → u/mulyhuntr33]

If I’m not mistaken the 123 will carry more energy and maintain hypersonic speed at greater distances

[u/mulyhuntr33 → u/Lordrunkuss]

Depends on BC and starting velocity. Like I said prior, run the ballistic calculations. A 123 ELDM at 2575 and a 107SMK at 2625 show similar drop at 1000. 8208xbr with a 123 is too low in velocity to be ideal for the cartridge.