Dangerous 6.5 Grendel loads?

[JLT]

My brother also likes the XBR 8208 powder, the problem is it's not as available as most powders, into days world, even at that it takes more of the 8208 to do what AR Comp does, I can also add a few tenths of a grain and get a tic more velocity if I so decide to do so, but it's not necessary for my needs, I target shoot only, don't hunt, to me accuracy is more important than velocity! YMMV

I compete and I hunt. I shoot the Grendel in AR Tactical class on occasion and, more often than not, my 1:8 twist 20" AR will clean the target at 600 with > 50% X count. My match load is 29.0 gr. of 8208 behind a 107 SMK, Tula primer in Lapua brass. I can push it harder, but I don't need to. It shoots remarkably tight at 100 for an AR - half minute on a bad day, much smaller most days.

Good case fill - 90% of case capacity or better - is generally considered to be a good thing as far as precision is concerned, and I'm among those comfortable with that consideration. I've had more success with powders that fill the case than those that don't. For example, I stuff as much RL-16 into a Dasher case as I can behind a 105 Hybrid and I'm more than happy with the results. I might be able to match the velocity with 4 grs. less of H4895, but pressure would be higher, and I rather doubt that precision would be as good. In fact, I have tried AR-Comp in the Dasher, and it performed well, but RL-16 did measurably and consistently better.

To each his own, but you may want to experiment a little with a powder that will give you greater case fill. You might find something you like.

 

[DLT]

Was that new brass ? And could the flash hole have been too big ?

 

[Jester]

Just for reference.

I find it interesting that the 'accuracy load' is A2460 at max charge

 

[Jester]

Last thing I will say is the primers you are using are too soft! you need the CCI #450 or the CCI #41 primers

I do have CCI #450 that I bought for my 6.5 Creedmoor small rifle primer brass. I could work up a load with those, but why do you recommend them for a 6.5 Grendel bolt gun? I could see them being beneficial in cold weather, but I thought they might be a liability in this heat.

 

[Jester]

Was that new brass ? And could the flash hole have been too big ?

Yeah this was new brass and I took these pictures after firing it once and cleaning.

 

[Jester]

Some barrels are fast, some are slow. Some reloading manuals are close to what you have, some are not.

For example, Hodgdon lists 26.8 grains as the max load for that bullet with 2460.

I would like to see pictures that are not super close-ups. Just like a borescope, pictures that are too close will accentuate things to the point where they look bad, but actually aren't.

Did you start in the middle and work your way up, or did you just go to 27 grains and try the one load?

In regards to the rings, how clean was your chamber? I assume you cleaned the gun prior to shooting it. Did you use a bore guide? Did you dry out the chamber good before shooting? Those look like soot rings to me.

I know you didn't ask for another close-up picture, but I believe you're spot on. These lines do look much more like a surface stain than deformation. I'm starting to feel like I'm probably on the warm side, but I don't think I'm in dangerous territory. Bolt lift feels good and the primers don't have sharp corners. I'll back off a half grain to see if the cratering goes away, and I'll track the case length to see how much the brass is growing. I'll invest in a bore guide as well in case my sloppy cleaning was the cause.

 

[Konocti's Wigwam]

You load is a gnat's over the max. (26.8 in Winchester brass -Hodgdon's)

No, your wrong.

The Hornady App shows 27.6 max load (2400 fps) for a 123 grain ELD-M.

 

[NZ_Fclass]

No, your wrong.

The Hornady App shows 27.6 max load (2400 fps) for a 123 grain ELD-M.

Hodgdon does say 26.8g. I guess Hornady know their brass - and Sierra agree. Interesting that TAC and PPV produce the highest velocity, and I can attest that PPV and 8208 produce the best accuracy ( in my Howa, anyway)

https://sierrabullets.wordpress.com/wp-content/uploads/2017/11/sierra-bullets-65-grendel-load-data-112817.pdf

 

[Mark611]

As far as primer's go the 450 or 41 should give a better burn to the powder, I have also used the Winchester SRP's with my loads, I'm also using Starline and Hornady brass, the best combo I have is using either brass with AR Comp and CCI#41 primers, I was not getting the results I want until I put this combo together, my rifles are not match rifles, and I'm quite happy with 3/4'' groups @200m, but I also build my ammo like I build ammo for my precision target rifles

 

[Konocti's Wigwam]

Hodgdon does say 26.8g. I guess Hornady know their brass - and Sierra agree. Interesting that TAC and PPV produce the highest velocity, and I can attest that PPV and 8208 produce the best accuracy ( in my Howa, anyway)

In the same light, I load H335 to 28.0 grains with a Barnes 120 grain TTSX. Go on the Hodgdon site and they have data for the 120 grain TSX, the loads are pretty much the same (Barnes shows the same load for both bullets). Hodgdon shows 26.6 as the max charge. Now grab the Barnes data from their site, the PDF shows 28.0 grains as the max charge. Who would you believe? I tend to go with the bullet manufacture. FWIW, I use Starline brass.

I consider 6.5 Grendel one of the most forgiving cartridges to load for, since the velocity low. Everything is SAAMI and it is one cartridge I never need to trim necks. Maybe I've just been lucky.

I also load 8208 and Varget but have about 5 lbs. of H335 sitting around...My preference is Varget, 8208 and H335 in that order.

 

[Oso]

I have a Howa Mini and have seen similar marks, but also in an AR15. It appears similar to case separation, which is disturbing after 1x-2x firings. The cases lengthened as it fireformed to the chamber, but not in any excessive manner. As with your picture I have at times encountered multiple banding lines that circumnavigate the case. However, when each case is inspected with a feeler probe (bent paperclip) there aren't any variations/inconsistencies along the case wall ... no ridges or troughs. These marking go away when tumbling your cases. I sure at some point in time I even posted about this exact "issue" on a forum.

We are dealing with mass production chambers. I think what is happening is some of the gas is back drafting down the case and getting trapped in micro imperfections along the chamber wall (tooling marks caused by minute chatter or worn reamer blade). Inspection of the cases shows the marks to be superficial and they go away when the brass is tumbled. I keep a watch for excessive case growth or expansion.

As far as powder AR Comp and H4895 are my powders of choice for heavier bullets (123gr SST) in the 6.5 Grendel. These two powders are near identical in performance at almost the identical charge weight.

CFE 223 is second fastest powders, with LeverEvolution being fastest. Both of these work great pushing heavies without the pressure spike that other powders might generate. 8208 XBR works better with bullets less than 120gr class. Almost every other powder good for .223 works for the lighter bullets in Grendel.

 

[Jester]

Thanks for all the information, guys. I backed off to 26.0gr of powder and the cratering is barely there. It was only 91 degrees today, but I'm confident this load will still be safe in 100+ degree temperatures, which is my main concern at the moment. My first 3 shots averaged 2280fps with a SD of 4.7 and ES of 7 (not statistically significant, I know, but definitely promising.) I fired the remaining 27 rounds with a suppressor mounted and there were still no pressure signs, but the LabRadar didn't trigger so I couldn't verify the numbers.

I appreciate all the powder recommendations. I'll order some lighter bullets to test as well. I'm really enjoying this cartridge and rifle combo, since it's super handy and doesn't wear me out to carry or shoot.

 

[JLT]

Thanks for all the information, guys. I backed off to 26.0gr of powder and the cratering is barely there. It was only 91 degrees today, but I'm confident this load will still be safe in 100+ degree temperatures, which is my main concern at the moment. My first 3 shots averaged 2280fps with a SD of 4.7 and ES of 7 (not statistically significant, I know, but definitely promising.) I fired the remaining 27 rounds with a suppressor mounted and there were still no pressure signs, but the LabRadar didn't trigger so I couldn't verify the numbers.

I appreciate all the powder recommendations. I'll order some lighter bullets to test as well. I'm really enjoying this cartridge and rifle combo, since it's super handy and doesn't wear me out to carry or shoot.

Jester, get a recoil trigger for your LabRadar. I've never had a failure to read while using one.