6mm Grendel help

[lawrence97]

So I have an upper from Atheris and I am running a 22” Tbox barrel and an adjustable gas block. I’m experienced reloading and I use a Prometheus and AutoTrickler v3. I’m also experienced shooting. I have verified scope and everything else is tight.

I am using Hornady brass, Redding Grendel bushing dies (.267 bushing), h4895, varget, rl15, AR comp, leverevolution and CCI 450’s. For bullets I have tried the Sierra 107’s, Sierra 90gn gamechanger, Berger 105 hunting VLD and 87 vmax. Unfortunately I have not been able to locate some imr 8208 xbr to play with locally.

Are these typical results from a 6mm grendel gas gun or are my hopes set too high?
I would like for it to shoot consistently in the .75moa range at the bare minimum. I know many post some tight 3 shot “wallet groups” but I need it to shoot consistently.

Any advice or observations would be greatly appreciated.

*Not sure why the pics are sideways*
Feel free to PM me your number and I can txt some better pics.

 

[Birddog6424]

How do you know you're on the accuracy node? It's pretty hit and miss to load this and that and shoot for groups and have it all come together.

Pick one bullet, one powder, and find the load for it. If you dont like it, try another. It looks like you are using different powder and bullets and shooting 4 groups in .5 increments. If this is 100 yards, it's too close for a shot string test. Your .5gr powder gap is too far apart for OCW testing.
So I'm not sure what your methodology is here.
It would be luck to have something show up like this.

 

[lawrence97]

I am trying to hit higher nodes for velocity and to take advantage of bullet BC.
Quick load gives me a parameter/max pressure and I will run a few charges in .5 grain increments to see if there’s something worth exploring. I’d hope to find a node that is at least .3-.5 tenths of a grain wide. This is coarse load development to see what powder/bullet combo do on paper and with the chrono.

 

[Birddog6424]

It seems very loosy goosy to me. Kinda poking around. You've fired a lot of rounds there, and I can only speculate how long you spent at the reloading bench.

I usually fire about 12 rounds into a ditch bank, then about 5 four round groups, and I'm done.

I'm scratching my head with you here.. Good luck with it.

 

[FCS]

Gas system length? Rifle length or +2" gas?
Buffer weight?
Trigger?
Butt stock type?
When shooting groups, bipod and rear bag or ???

0.5 gr increments for Grendel size case is a bit too course, 0.3 gr would probably work better.
27.0 - 27.5 of H4895 with 107 deserves a little more investigation at 200 or 300 yards.
I'd probably try 27.0, 27.2, 27.4, maybe as high as 27.6 at longer distance to see what vertical looks like.

I wouldn't be changing powder and jacket material, creates more variables. Each time you change, need 3-5 rds for barrel to settle back in. Well known issue and reason HP shooters try to run a single powder / jacket material at all lines. If it shows up when shooting 1 MOA target, going to mess up your sub MOA hopes.

107 SMK, 22" barrel you'll be looking for 2700 ish fps or less.
H4895, RL-15, Viht N-540 or similar are what you'll want with 105-107 gr bullets.
8208 is going to be a bit too quick in burn rate.
AR-comp you'll probably pressure up before desired velocity.
Varget you'll probably run out of case capacity before getting desired velocity.
RL-15, Norma 203-B, Viht N-540 are probably your best bets for running heavier bullet at increased velocity.

 

[lawrence97]

Gas system length? Rifle length or +2" gas?
Buffer weight?
Trigger?
Butt stock type?
When shooting groups, bipod and rear bag or ???

0.5 gr increments for Grendel size case is a bit too course, 0.3 gr would probably work better.
27.0 - 27.5 of H4895 with 107 deserves a little more investigation at 200 or 300 yards.
I'd probably try 27.0, 27.2, 27.4, maybe as high as 27.6 at longer distance to see what vertical looks like.

I wouldn't be changing powder and jacket material, creates more variables. Each time you change, need 3-5 rds for barrel to settle back in. Well known issue and reason HP shooters try to run a single powder / jacket material at all lines. If it shows up when shooting 1 MOA target, going to mess up your sub MOA hopes.

107 SMK, 22" barrel you'll be looking for 2700 ish fps or less.
H4895, RL-15, Viht N-540 or similar are what you'll want with 105-107 gr bullets.
8208 is going to be a bit too quick in burn rate.
AR-comp you'll probably pressure up before desired velocity.
Varget you'll probably run out of case capacity before getting desired velocity.
RL-15, Norma 203-B, Viht N-540 are probably your best bets for running heavier bullet at increased velocity.

Rifle length gas system, standard rifle buffer, magpul prs gen 2 stock, and when shooting I use a bipod and rear bag.

I will usually shoot sighters on another target before shooting groups or making any changes.
As for h4895 I started to get some case punishment around 26.8 and that’s why I switched to RL15 with the 107’s.

 

[MotorOilMcCall]

I'm with the guys above.

Pick a bullet you want to use, and do a legit OCW test. Personally, I do that at MAX increments of 1% of the charge weight (so for a 20-30gr charge, 0.2gr increments). I've been using IMR 4895 (only in a week of loading thus far, but already found a good node in my AR15Perf 22" barrel, and I started witht hat because I had it on hand). Waiting for a new mount for my V3, so no velocity info, sorry. Within one outing I had found a load that was sub-MOA, so I'll fine tune with seating depth and neck tension from there. Once the chrono is working, it'll help me understand SD's and velocity better.

I've had good success with the 105 Berger's so far. The 85gr SGK weren't that impressive, but they are what they are, and will be fine for varmint hunting (1-1.5MOA was the best I got out of them, granted, that was after quite a bit of shooting the Bergers). 100gr SBT Sierra's are loaded, but I didn't get to shoot any before the rain started...

 

[RMB]

I have a similar set up...only a 20" 1/8 twist t-box and had the same issues. I was kinda throwing too many variables at the rifle. And, it was new to me (first gas gun).

I regrouped and started testing two powders (8208 and IMR 4895) at .3 grain increments up to 95% max loads note: I stopped and pulled the bullets if I noticed case swipe. One thing that helped was the addition of an adjustable gas block. As I do use a suppressor.

Long story short, the rifle only likes lighter bullets (87 grain Vmax and 95 SMK). Both bullets are very sensitive to the COAL. I don't have the data at hand but once I found the load for accuracy.. started using a better seating die it all really came together. Both will shoot right at .750" average if I do my part (multiple 5 shot groups). I am in the process of upgrading the optics and mounts. I hope that I can get down to .600".

For high volume or practice I use the 87 GR out to 300 yards...longer than that I use the 95 GR. My range card is based on the 95 gr.

Just for fun I tried the 58 grain vmax....lots of speed..but accuracy is "less than ideal".

 

[Yondering]

It does sound like a case of trying to change too many variables at once. Also -who's barrel do you have? (6mm Grendel is used generically, so not sure...)

Forget about 8208, that's not a good powder choice here unless you're shooting light varmint bullets. Varget actually produced decent velocity for me, but shot like dog poo with the 105gr.

My suggesting - grab your 105gr BTHP, Leverevolution, and CCI 450s in Lapua brass. Find your max charge and back off a little (that ended up around 31.0gr for great brass life in my barrels, YMMV.) Now do a seating depth round robin test, varying between .005" off the lands down to about 2.200". You'll find an optimum seating depth. For even better results, do this while varying the powder charge between max and about 1.0gr lower; this helps identify better what seating depth is really tolerant of velocity variations.

You might consider the result good enough to stop there, or go back and do an OCW round robin test to finish up, depends on your results and goal. This method has worked better for me in the past couple years than all the OCW tests I've done in the 20+ years prior without finding optimum seating depth first.

Seating depth is pretty key, and if you're not testing for it, you're giving up accuracy but also missing one of the most valuable aspects of the short Grendel case in an AR magazine.

FWIW the same method gave great results with the 90gr TGK and Lever as well. Even at the lighter 90gr weight, nothing beats Lever in this case size.

 

[Dewey7271]

Quick load gives me a parameter/max pressure and I will run a few charges in .5 grain increments to see if there’s something worth exploring.

No offense, but unless you’ve calibrated Quickload to what you’re actually seeing on the chrono then the calcs it spit out are a guess.
‘As the others said, one powder would be easier.
Take temp and chrono readings.
Pull up QL with that load.
Enter temp.
Then modify Ba until velocity matches what your chrono says.
Although it’s a rough calibration the output should now match what’s actually happening.

 

[sam4886]

XBR and benchmark have done pretty well with the 90 game changers in mine. Lever will give you more velocity, but I like to keep to more temp stable stuff personally.

I generally do load development by shooting whatever powder loads I want to test, everything but the charge being the same, shoot everything over the chrono and choose a charge weight based on groups and SD/ES, with more weight towards the SD/ES. After that, mess with length and neck tension and pick the prettiest groups. Done.

All that said, ARs are always a little tougher and you'll want to make sure everything else is absolutely perfect. Equipment, the gun, your form, etc. Just got done commenting on a thread about gas block clearance inside a handguard when the barrel starts whip. Something like that will fuck you up way more than a 3/10 grain charge difference.

 

[Rancid Coolaid]

Unless I am mis-reading, this is thread about reloading suggestions and accuracy potential all slammed up into one conversation, yes?

In short, Grendel can be quite accurate for a gasser, meaning sub-1 MOA with plenty of effort in shooting and reloading. That said, like any other caliber, it can suck if things aren't to that specific gun's liking.

If this is about accuracy potential in a SAAMI caliber, I usually start with factory ammo. If a gun sucks balls with factory stuff, it might tighten up with handloads, but it isn't worth my effort. On the flip side, if it shoots well with factory, I know I can tweak it to shoot even better by making small, reversible changes.

If a gun can't shoot for shit with good factory ammo, I don't waste time on reloads.

I like my Grendel, chews up ammo and does so with an acceptable level of precision and accuracy, but I'm not shooting that gun for tiny groups at long range. If that is your goal, determine inherent accuracy before you move forward with improving things. Without a baseline, you're kinda just flailing around hoping to get lucky without hurting yourself.

 

[Yondering]

XBR and benchmark have done pretty well with the 90 game changers in mine. Lever will give you more velocity, but I like to keep to more temp stable stuff personally.

Respectfully, there are probably at least 5 other common powders that are better choices than those two IMO. Burn rate is pretty important in these small cases and both of those are a bit too fast for best results; yeah they'll go bang but you're either leaving velocity on the table for no reason, or running a lot more pressure than necessary. I like both of those powders in the 6.5 Grendel and 5.56 but experienced pressure spikes that showed up before I expected in this cartridge. YMMV of course.

If you want temp stability consider one of the other stable powders that are a little slower. Even H4895 is enough slower to make a difference, and Varget is a step past that and generates good velocity, although it didn't shoot well with the 105 in my long barrel.

Also, I see a lot of you guys worried about temp stability with Lever, but in my 3 barrels, at least with the 105gr load, it doesn't vary nearly as much with temp as some of you think. I haven't played with the 90gr load in cold yet so don't know about that one. Temp stability varies a lot between different loads and different cartridges and is not a set value for a particular powder. Try it, you might be surprised. I was.

On that same note with Lever, I prefer to start my load development with a seating depth test to determine a load that's accurate with a wide range of powder charges. With the 105gr in my 243 LBC (another 6 Grendel), I found a seating depth that prints small groups with mixed powder charges between 30.0gr - 31.3gr. That's enough spread to maintain accuracy across a wide temperature range if the charge weight is somewhere in the middle; of course accounting for a velocity change at long range is still important but it's not moving out of an accuracy node just because the weather changed.

 

[sam4886]

No worries. I tried 4895 and didn't get anything spectacular, and it was also a bit slower than with XBR or benchmark. That doesnt mean it's not worth another look.

Also, I don't particularly enjoy load dev, so I find something acceptable and roll with it. Depending on how many other projects I accumulate by the spring I may try out some lever, var get, and 4895 again. I've got lots of varget laying around. With the ARC coming out, it'll be interesting to see what kind of stuff real factory testing might figure out as a ballpark for us 6 Grendel OG guys.