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New 6mm Advanced Rifle Cartridge
- Thread starter Gtscotty
- Start date
When I give you these numbers, keep in mind I’m operating at a 7000’ density altitude.
With the Hornady 105 BTHP at 2689 fps, at 500 yards, 2.7 mils and 977 FT LB of energy.
With the Hornady 105 BTHP at 2689 fps, at 500 yards, 2.7 mils and 977 FT LB of energy.
Sounds pretty much right on with what I've seen for the same bullet. My favorite shooting spot is 615yds across a canyon at 6,000' da, which takes 3.7 mils. While I can't verify 500 yards at that point (since it's out in open air
) it works out to 2.6 mils and 1,000 ft-lb, but my load starts off 50 fps faster too, so I think those numbers correlate really well with yours.CPD Duramags in 10/20/26 rds. No issues so far. Picture with all three sizes and a 18/10.5" barrel:
Those really look like 7.62x39 magazine bodies; is that what you bought or is that what CPD is selling as Grendel mags? The Grendel has even less body taper than the 5.56 and doesn't need that much curve in the mag. I'm a little surprised you're not having bolt over base malfunctions with that long one when it's full.
I use mostly 15rd & 17rd (both about the same length as 20rd 5.56 mags) ASC and ELander mags. Some complain about Elanders but they've been great for me, never had an issue across a bunch of different rifles. I use the same mags for both SPC and Grendel based rounds.
Also have some 25-ish rd mags in both brands and they work fine too, but I haven't used them nearly as much. I don't have much use for big mag capacity with the way I use these rounds. At the same time, the 10 round mags don't seem to offer any advantage that I can see (I'm not limited by mag restriction laws), so I don't buy them.
The 26rd does look like a 7.62x39 re: curve, but it's definitely stamped for Grendel. No issues at all. They were initially sold as 28rd magazines before all the rebranding from what I recall from forums back then, and worked reliably up to 26rds, but not more than. I haven't had any issues, but I also haven't put thousands of rounds downrange with them yet.
I can't get my 6.5 G E-Lander mags to run at all with the 6mm ARC, but they're absolutely fine with 6.5 G, 6.8 SPC, and .224V. Very puzzling.
Went out today with new 6.5G Duramag in 20 and 26 RD capacity for the first time. I like to be able to push that top round down a half inch when fully loaded, so for me these are 18 and 24 round capacity. Both ran without any problems through one cycle.
Also had new 6.5 G mags from ASC in 10 and 25 RD capacity. The 10 RD version worked fine but the 25 RD mag choked on the last five rounds. I even experienced an ultra rare double feed. Talk about a PITA to clear ....
This I do not necessarily blame on the magazine ... yet. I'm going to build up a new rifle with this same barrel and give this magazine another chance. I'm not 100% sure everything is perfect in this specific receiver set and forend combo.
Fired 80 rounds today. What a filthy gun after this. Never seen a gun produce such nasty brass.
Got my first case of Hornady 108-ELD. The Hornady 105 BTHP easily outshot it.
Went out today with new 6.5G Duramag in 20 and 26 RD capacity for the first time. I like to be able to push that top round down a half inch when fully loaded, so for me these are 18 and 24 round capacity. Both ran without any problems through one cycle.
Also had new 6.5 G mags from ASC in 10 and 25 RD capacity. The 10 RD version worked fine but the 25 RD mag choked on the last five rounds. I even experienced an ultra rare double feed. Talk about a PITA to clear ....
This I do not necessarily blame on the magazine ... yet. I'm going to build up a new rifle with this same barrel and give this magazine another chance. I'm not 100% sure everything is perfect in this specific receiver set and forend combo.
Fired 80 rounds today. What a filthy gun after this. Never seen a gun produce such nasty brass.
Got my first case of Hornady 108-ELD. The Hornady 105 BTHP easily outshot it.
I have 2 10 round and 2 15 round ASC mags that I use for my 243 LBC. I haven't used the 15s much, but haven't has a single problem with any of them.
ASC now makes 6mmARC specific magazines
https://www.ammosc.com/categories/ar-15-magazines/6mm-arc.html
https://www.ammosc.com/categories/ar-15-magazines/6mm-arc.html
I have a 6ARC barrel coming from Compass Lake. It’s a 20” with a 7.5 twist. I’m wanting to shoot 105s through it but also some lighter 60-70gr bullets. Has anybody had an issue with a lighter bullet and fast twist?
I’m going to rebarrel a ruger American 6.5 grendel to a arc, any reason to not go with a 8 twist? Or should I do 7.5?
I’ll be running 105+ weight bullets. What’s best barrel length for this?
I’ll be running 105+ weight bullets. What’s best barrel length for this?
7.5 twist is more optimal for the heavier bullets. Any reason to not use a 7.5 which most of the manufacturers have standardized on? 8 twist will probably be fine, I just don't see why you'd go that direction unless you want to shoot the really light stuff.
7.5 won’t hurt you any, gives a bit of insurance for the heavier bullets.
I wouldn’t go shorter than 18” nor longer than 22“ but depends on how you really want to use the rifle.
18" Bartlein barrel with factory 108 ELD-M, as measured by a Labradar. This was shot suppressed, FWIW, and was from the first box of ammunition through this barrel:
AVG: 2643.25
SD: 4.026696626
I plan on for a while leaving mine in the plastic stock so I’ll probably roll with a 20” barrel
aarrgghhh!!!
So I couldn't get N540 and either a 105gr Berger Hybrid or 95gr TMK going without pressure signs. I was so excited with the potential for the 95gr TMK, thinking 2800fps was possible from my 20" Craddock.
Loaded to 2.25" and at 40*F, here are my results:
105gr Berger Hybrid and N540:
95gr Sierra TMK and N540:
To illustrate this, I'm attaching a loaded 95gr TMK at 2.25", next to the 95gr TMK, the 105gr Berger Hybrid and the 110gr SMK (these are all the 9mm bullets in my inventory.
If anyone has any reloading suggests, please post them up. Thanks
So I couldn't get N540 and either a 105gr Berger Hybrid or 95gr TMK going without pressure signs. I was so excited with the potential for the 95gr TMK, thinking 2800fps was possible from my 20" Craddock.
Loaded to 2.25" and at 40*F, here are my results:
105gr Berger Hybrid and N540:
- 28.0grs - 2603fps AVG, 9 STD. Slight pressure sign. Outstanding precision, 0.5" at 100
- 28.5gr - 2656fps AVG, 12 STD. Pressure signs. Outstanding precision, also 0.5"
95gr Sierra TMK and N540:
- 28.5gr - 2685fps AVG, 21 STD. Pressure signs. Outstanding precision, 0.75"
- 29.0gr - 2723 fps AVG, 15 STD. Pressure signs. Don't know on precision, as I was shooting steel at 400yds.
To illustrate this, I'm attaching a loaded 95gr TMK at 2.25", next to the 95gr TMK, the 105gr Berger Hybrid and the 110gr SMK (these are all the 9mm bullets in my inventory.
If anyone has any reloading suggests, please post them up. Thanks
The only powders that will reliably get you past 2800 with a 95 in a 20” are Lever and CFE223. The best substitutes are at least 50-75 fps slower.
These small cases are very picky about powder when pushed to this level, they just don’t have the flexibility in powder choices as bigger cases like the Creedmoor or 308.
CFE223
LeverEvolution
Maybe AA 2520
ETA: FWIW, I'm getting sub-MOA results with all three of the above for 10 shot groups with my Proof 18" AR-15 barrel with 108 ELD's and 105 HPs.
How's temperature sensitivity loaded at accuracy nodes in this cartridge, now that there's been a seasonal change? I'd be curious about CFE223/Lever in that regard. I just finished processing some brass so will be able to do some testing with CFE223 soon enough as I do have some on hand, see if a 30F temperature differential like we see daily causes major velocity changes, let alone the issue with rounds sitting in a warm chamber in an AR15. I know a lot of sensitivity can be cartridge specific, so perhaps it's not as bad in the 6mm ARC as it is in some other cartridges (which have awful swings of > 1FPS/degree).
If I have done temp tests with CFE223 in this cartridge I don't remember the results well enough to say definitively, but they're going to be worse than Varget, for example. I'd expect somewhere around 1.5-3fps per degree F (Varget/H4350 etc.. are usually .3-.5 fps/deg). I have 1.2 plugged into 4DoF for my LeverEvolution loads. It's the compromise a guy has to make. I think I've stated it before, but IMO the velocity swings aren't a huge issue for me because the AR-15 is for hunting, where I'll rarely shoot past 400yd ever. And in the bolt gun (PRS/NRL competition) I use 4DoF every stage and it takes care of temp variable MV.
A tangent, but you mentioned nodes... The testing I've done so far with large sample sizes (20-35 shots per 'variable change') has shown that powder charge accuracy "nodes" don't exist. Dispersion stays at a low level until a certain threshold at which point adding more powder just makes group size increase. Even going as much as 2-3 grains over max book load the trend continues worse for dispersion. I'd like to try it in more barrels before I say anything definitively, but the trend has stayed in 3 different calibers, and across 6 different powder types in one of those calibers. A lot of data can hide in 5-shot groups, and my thought is that this idea of sinusoidal 'nodes' is a reflection of noise being sinusoidal.
A tangent, but you mentioned nodes... The testing I've done so far with large sample sizes (20-35 shots per 'variable change') has shown that powder charge accuracy "nodes" don't exist. Dispersion stays at a low level until a certain threshold at which point adding more powder just makes group size increase. Even going as much as 2-3 grains over max book load the trend continues worse for dispersion. I'd like to try it in more barrels before I say anything definitively, but the trend has stayed in 3 different calibers, and across 6 different powder types in one of those calibers. A lot of data can hide in 5-shot groups, and my thought is that this idea of sinusoidal 'nodes' is a reflection of noise being sinusoidal.
Sinusoidal... good word, I like it!
Anyway, I will get some CFE223. I was hoping a extruded powder would get the job done, but looks like I need ball. I can handle the temp swings on the ballistics, as I have a Kestrel AB that models the curve, but I don't want to run into pressure issues at the higher temps (for example, yesterday's testing was at 40*F - those loads would have been dangerous at 90*F.)
Thanks for the input all.
Wrong burn rate. I spoke with them about a variant that might be a better fit, they said they're evaluating things now, but nothing on the near/mid-term horizon, it'd be at least a year out, _if_ it happened. I agree, it'd be a great fit.
Yeah 6.5 StaBall is closer to H4350 for burn rate. Too slow for this little guy.
I’m with you. I have an 8lb jug. I’m building a coyote gun. Hoping that I can shoot a 90gr around 3000fps out of a 20” barrel.
I took apart one of Hornady’s Black with 105s. It had 30.8gr of some ball powder. It was compressed to say the least.
8208 was one of the first powders I used and it did pretty good. Was down on velocity a little and I moved on to CFE223. I am now using Leverevolution and have found the node that is a happy medium for velocity and accuracy with it.
I tore down a Hornady 105 today and weighed it with my beam scale and I got 29.7gr of what looked like CFE22.
Hornady powder on left. CFE223 on the right
I tore down a Hornady 105 today and weighed it with my beam scale and I got 29.7gr of what looked like CFE22.
Hornady powder on left. CFE223 on the right
Attachments
Interesting they are using CFE223 (or what looks like it) - picture is a little blurry but that looks like straight CFE223 and not a blend. Happen to pull a 108gr as well? I like the additive package in CFE223 and have 8lbs here to test. I just fired and cleaned a bunch of brass this weekend so will be loading soon. Still keeping my fingers crossed that I can get decent velocity our of AR-Comp and not worry about anything else, I just wish I had a pressure testing system to get 'real' numbers. I looked at the Pressure Trace II but it's hard to mount on an AR15 and the numbers may or may not be accurate in absolute terms, only relative.
The only thing different between the 105's and the 108's is the bullet. same powder weight same powder. I am in the process of loading some rounds right now. I am going to load 5 rounds of 105's with 29.7gr of CFE tomorrow, and maybe 5 rounds of the 108's as well. I have already loaded Leverevolution to 29.7, and they shoot very well, way better than the factory stuff. My go to load for .5 MOA is 29.4gr of Lever behind a Nosler RDF 105 HPBT, it's my pet load for these guns. Between my sons 20" Faxon and my two 18" Odin and Faxon barrels they all seem to love this round. they shoot better than the Hornady 108EDL's even at distance.
Between yesterday and today I processed 800 pieces of brass ready to drop powder and seat bullets. With this round I hand load all of them, I do have a Frankford Intellidropper that speeds thing up pretty good.
My press has a powder drop but I only use it for .223 and pistol stuff. I got to hit reloading hard the next couple of weeks, 4000 .223, 2000 .45 ACP, 3000 .40 S&W. Only thing I got going for me is all my brass is already processed, and I have all the powder and bullets.
I'll try to get a better picture of the powder.
Between yesterday and today I processed 800 pieces of brass ready to drop powder and seat bullets. With this round I hand load all of them, I do have a Frankford Intellidropper that speeds thing up pretty good.
My press has a powder drop but I only use it for .223 and pistol stuff. I got to hit reloading hard the next couple of weeks, 4000 .223, 2000 .45 ACP, 3000 .40 S&W. Only thing I got going for me is all my brass is already processed, and I have all the powder and bullets.
I'll try to get a better picture of the powder.
Yeah there's a family of non-cannister ball powders (Upwards of 5-10 different powders between CFE and StaBall) that are the same size/shape but different burn rates. It's not uncommon for ammo makers to mix them to tune the burn rate for a given cartridge.
I don't doubt it, I'm just saying it is pretty darn hard to tell much from a picture in terms of burn rate.
Lots of canister grade powders available to ammunition manufacturers that are not available to public.
8208 works pretty well in 6.5 Grendel but is a bit slower than what one can get using a double base powder as you pressure up sooner. 6 ARC that will be case but even more so as smaller bore. 8208 will work but with heavier bullets I'm pretty sure you'll pressure up before getting desired velocity.
N-540 pressuring up with 95 & 105 before desired velocity, you can expect 8208 to do same but slightly lower velocity since 540 is slower in burn rate.
I've been shooting the 243 LBC for almost 4 years (so a lot more than one seasonal change; don't forget this 6 ARC isn't a new concept), and with Lever and the 105BTHP I've seen less than 30 fps difference between 20°F and 95°F in my 24" barrel, and by finding an accuracy node with the right seating depth my load can handle more variation than that without moving out of the node. Of course if you change the barrel, seating depth, powder charge, etc that can change, so your results will vary. I haven't checked if it holds true in my shorter barrels.
Barrel length shouldn't impact it significantly, that's great information. It's worth a shot I suppose. Too bad I have CFE223 and not LVR at this point. I need to figure out a way to sell off powder locally, I have the opposite problem of most!
So question for the reloading experts:
most of the powders we are discussing - CFE223, Leverevolution, N540, BLC2, 2520, etc - are all very close to each other on the burn chart. So why does the pressure curve look different? Is it because of differences in volumetric characteristics of each? For example, does CFE223 have a lower volume requirement than say N540, allowing it to produce lower initial pressure and then generate 'push' further down the barrel?
RE the questions on magazines from @DeSnifter - I can't recommend ASC mags. I'm getting some FTFs w/ them... maybe its something else, not the mag, but its spotty right now.
most of the powders we are discussing - CFE223, Leverevolution, N540, BLC2, 2520, etc - are all very close to each other on the burn chart. So why does the pressure curve look different? Is it because of differences in volumetric characteristics of each? For example, does CFE223 have a lower volume requirement than say N540, allowing it to produce lower initial pressure and then generate 'push' further down the barrel?
RE the questions on magazines from @DeSnifter - I can't recommend ASC mags. I'm getting some FTFs w/ them... maybe its something else, not the mag, but its spotty right now.
This has been asked/answered a lot in this thread. One last time for me.
CPD Duramags, 10, 20, and 26rds. I've posted comparison pictures a few times if you look back in this thread. I've had no issues with any of them. I've grown fondest of the 20rds, they still work with my TBAC bipod but have good capacity.Similar threads
