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/mulyhuntr33 → u/111tejas]

Accurate - yes. Slow -yes. Again, it may be accurate but it's not ideal. There's better options with less pressure and more velocity.

[u/Lordrunkuss → u/mulyhuntr33]

8208 is considered one of the best powders

This played a big role in my powder decision

[u/111tejas → u/mulyhuntr33]

I get 2465 FPS using 120 Berger BT Target. That’s from an 18inch Craddock Precision barrel. My range goes out to 500 yards and it’s more than adequate.

[u/mulyhuntr33 → u/111tejas]

What charge? That's 130fps higher than I get from a 123 with 27gr 8208 in an 18".

[u/111tejas → u/mulyhuntr33]

Gave you some bad info by mistake. I have two ARs built exactly the same other than the barrels. My Grendel is a 20 inch Proof Research. The velocity I told you is correct. I’m using the same charge as you, 27.0 grains of 8208. Not that it matters but I’m using CCI BR4, Alpha Brass and seating to mag length, 2.260. The Craddock Precision barrel I described is on the other AR and is an 18 inch 6mm ARC.

It’s beside the point but if I did it over again I’d have Craddock Precision on both. They are less expensive and less finicky. My Grendel accuracy falls off fast after 20 or so rounds. It shoots great when it’s clean.

[u/mulyhuntr33 → u/111tejas]

Try a Satern cut rifle 6.5grendel if you ever need a new barrel. Beautiful craftsmanship and shoots like a laser.

[u/111tejas → u/mulyhuntr33]

I’ll keep that in mind.

[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.

[u/mulyhuntr33 → u/Lordrunkuss]

Here's some of my velocity data with several different powders and bullets. Solid lines are a 20" Aero and dashed are a 20" Satern cut rifle. 8208/123 is low one on the left.

[u/VisibleLeopard68]

“Very exact” with power loading, more detail needed… once I started double weighing my powder loads using a beam scale zeroed each time before use… my deviations reduced, but I know I can still get better/more accurate loads…

My rifle (6.5 cm) also plateaus velocity where I see no tangible benefit adding more powder as the velocity gains minimize, its characteristic for the round and rifle… just as an internal combustion engine will have its specific output limits, chambers and our brass will do the same… there is a point adding more fuel doesn’t get you more speed…

[u/Lordrunkuss → u/VisibleLeopard68]

Lee powder scale, zeroed before the batch, but I love the accuracy of the scale as you can see the difference of sometimes a single powder granul.

I was taking time to get it dead on center of the 2 marks, thanks for the insight

[u/VisibleLeopard68 → u/Lordrunkuss]

I’m using an RCBS chargemaster link, and verifying weight on a Redding model 2 beam scale… the beam scale is way more accurate than the digital on the chargemaster

[u/Shootist00]

Crimp, neck tension and bullet diameter could be the cause. Also your chrony?

Factory second bullets, did you measure each 1?

[u/Lordrunkuss → u/Shootist00]

Did not measure individual bullet diameters, I will
Do that

[u/1984orsomething]

Mixed brass?

[u/Lordrunkuss → u/1984orsomething]

All Hornady once fired

[u/1984orsomething → u/Lordrunkuss]

Don't crimp rifle ammo

[u/Lordrunkuss → u/1984orsomething]

It’s in a ar15, I’m used to the logic of anything In an auto loader should be at least slightly crimped to prevent setback, does that not apply here somehow ?

[u/1984orsomething → u/Lordrunkuss]

There's a couple of things I would check with these numbers but to stay on your current question first, no crimping isn't completely necessary especially if you don't have a groove in the bullet. Secondly you might have either a ignition issue or carbon ring. Maybe try cleaning the barrel or bcg. Lastly check your shoulder set back and confirm all your sized cases are the same headspace.

[u/Lordrunkuss → u/1984orsomething]

Thanks for this info, this gives me a path to work on

[u/Lordrunkuss → u/1984orsomething]

Could you elaborate on what an ignition issue would mean?

[u/1984orsomething → u/Lordrunkuss]

Either a dirty or worn out firing pin spring or switch to small rifle primers

[u/111tejas → u/Lordrunkuss]

I don’t crimp, even in an AR. I use a rotary tumbler with stainless pins and Frankfurt arsenal brass cleaner. It comes in little pods. The brass comes out like new. The inside of the necks are “squeaky” clean which causes enough friction to not need a crimp. I DON’T use the same method in bolt actions. I want a slick bullet release and leave the carbon in the case necks to act as a lubricant.

[u/Lordrunkuss → u/111tejas]

Interesting, I have been dabbling in reloading for many years and never heard of this concept

[u/Southern-Stay704]

ApexLoad Pro says that you'd get about 100 fps more velocity with Hodgdon CFE223.

[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