Need advice - 6 ARC bolt action load data for 103-108 gr bullets

[Mr. Wolf]

(edited: Retitled for subject accuracy)
Time to draw up plans for a winter project.
A few years ago, I wanted to really get into the 6 ARC in a bolt gun but I wasn't fond of the temp sensitive powders (CFE223 and Leverevolution) folks were using to get to 2900+ fps. My goal is to reach 2800+ fps with a 26" barrel, 1:7.5 twist, bolt action using Hornady 105 gr BTHP, Alpha OCD brass, CCI SR magnum primers, and Winchester Staball Match powder.

With the release of Winchester Staball Match in Jan 2023, the new powder got my gears turning again. Staball seems to slot between Varget and CFE223 in the burn rate chart and temp stability tests show reasonable stability for the Staball XX line of ball powers.

Anyone with experience on with similar combination with getting their ARC bolt guns with 105 gr bullets to 2800+ fps?
Any available info for max pressure and expected velocities on QuickLoad?
Link to Rob's reloading test with 105 gr BTHP and 28.5 gr Staball Match on a 22" rifle got 2699 fps and SD 16.5.

(Hornady's site doesn't list Staball Match reloading info and Hodgedon's site doesn't have bolt gun info nor the 105gr BTHP listed)

Thank you in advance and happy shooting

 

[Defender32]

Hogdon will only give you data on the 6 ARC to the AR MAX Pressure.

I would load 3 at 27.6 and see what my velocity is and work up from there. You will not have issues getting the speed. The accuracy of the load could be the issue. I am at 30.2 of CFE 223 for my 112 Match burners in a 22" & 26" barrel. If my ammo is kept in my pack on hot and cold days my velocity does rise. I have a temp table of that ammo built 10* to 120* and my data lines up great to 1275. I typically get to shoot 2 PRS Matches a year due to all my rimfire matches.

22" Barrel is 2700 FPS Average
26" Barrel is a 2820 FPS Average.

The 22 ARC and 6 ARC are hunting calibers for me mainly w/ a match at random.

 

[Mr. Wolf]

Defender32
Good info, thank you.
I've read that Hornady 108gr ELD-M Match and 105gr Black ammo exceed their listed bolt gun data.
I'm sure that they load with a margin of safety since there is a good chance that someone will use it in a converted AR-15 setup.

Anyone aware of what powder the Hornady box ammo use?
When my ammo and dies arrive, I hope to deconstruct it, weigh the charges and attempt to replicate best I can.

Appreciate the advice, keep 'em coming.

To carry the conversation along, I'll drop this recoil energy calc graph from ShootersCalculator.com
If 2850 fps can be safely reached with a 26" barrel, it may translate to an advantage to consider for PRS type shooting.

 

[Defender32]

Hornady uses a special blend of powder that is not available to the market. Or this is what I have been told/ heard.

 

[RyanWW]

Hornady black line is aimed at semi auto Rifles.

 

[Mr. Wolf]

Agree, black line is geared towards the AR platforms, but even the 108gr Match has AR-15 platform in the product description.
Typically, gas gun pressures maxes out at 50k psi and bolt guns go higher to 62k psi.

So if the Hornady box ammo is designed to top out at 50k psi with listed 24" barrel resulting in a muzzle velocity of 2750 fps, it stands to reason that there may be some headroom for speed for a bolt gun. I've read that some have seen higher velocities from the factory ammo with longer barrels. However, I've not seen any temp stability testing with the Hornady ARC box ammo. Hope to do that as well concurrently during load dev.

Some suspect that Hornady might be sandbagging the load data to sell their ammo.
I'll be doing tests with Alpha brass and CCI 450 magnum primers or possibly disassembling and reusing the box ammo powder for a ladder test.

Appreciate the info/advice.

 

[RyanWW]

I'll be following this closely. I hope to try staball match in my 6mm arc.
If it helps I get 2580 fps with hornady factory 108eldm and 2560fps with 105 black. Out of 16" bolt gun. Both shoot lights out at 500m but the match is more consistent.

 

[Mr. Wolf]

From Hornady’s official intro video of 6 Arc.
Looks very similar to CFE223/LeverEvo/Staball Match.
I’ll have to weigh and shoot the box ammo next to the same charge of Staball Match hand loads and possibly do a temp sensitivity test along side it.

 

[Mr. Wolf]

Update:

Used a kinetic bullet puller to examine the powder and took measurements.

Hornady 6 ARC Black 105 gr | Hornady 6 ARC Match ELD-M 108 gr

Total wt 254.8 gr | 258.2 gr
Bullet wt 104.8 gr | 108.1 gr
Powder wt 31.0 gr (compressed) | 30.1 gr (compressed)
OAL 2.206" | 2.250"
CBTO 1.728" | 1.704"
Base to datum 1.184" | 1.185"
Case length 1.481" | 1.481"
Neck diameter, loaded 0.270" | 0.270"

Comments:
1. For both factory ammo, powder fill is almost up to the neck, definitely a compressed load as I reseated the bullet to original CBTO. (photo 1)
2. Ball power is very similar in size to Staball Match but slightly darker (photo 2).
3. Also similar to CFE223 but slightly more uniform in size but same color (photo 3).
4. Load data from Hornady matches up almost exactly with CFE223 for 103-105gr bullets (photo 4).

Once I have my barrel, I'll chrono the factory loads that's been cold stored, room temp, and warmed with a pocket warmer.
Once I have brass, I'll ladder test for velocity with CFE223 and Staball Match.
Final consideration, the Hornady Podcast had 4 shooters talking about their PRS and NRL Hunter cartridges and the cartridge they started, went 6 CM, then to 6 ARC bolt and gas gun, then considering going back to 6.5 CM.



Stay tuned.

 

[RyanWW]

Thank you for doing this, I think it's very interesting.

 

[MEdude]

Your sharing of data is much appreciated.

 

[4O6shootist]

Update:

Used a kinetic bullet puller to examine the powder and took measurements.

6br velocity, 6br charge weights, from a case that holds 4-5gr less volume. That factory ammo gotta be running pretty high on the psi scale, and guys are running factory ammo loaded at that spec in gas guns all day. But they only recommend that data for bolt guns........that's kinda odd? I think the arc is a great lil cartridge, especially for its size, but now I see how it's getting all that performance. Anyone tested the temp stability of factory ammo? Freeze some, some room temp, some wrapped inside a beanie with hand warmers?

 

[Ledzep]

StaBall Match is slightly slower burning than Varget. I doubt you can get enough in the case to get velocity better than Varget. Unfortunately the trade off is usually +100fps for 62ksi over 52ksi but -70-150fos for temp stable powders (Varget level temp stable). StaBall Match and StaBall HD are as temp stable if not moreso than the hodgdon extreme powders.

In 26-28" boltgun barrels I get 2740-2780 with a 110 ATip with 27.5-28.0gr Varget @2.350".

I don't have StaBall Match data for ARC but I'll make sure it's on the list for our next manual.

 

[CollarChoke]

@Ledzep so I've been going down the rabbit hole with LeverEvolution loads in my 20" 6ARC bolt gun (see: https://www.snipershide.com/shooting/threads/6mm-arc-bolt-action.7171525/post-11823998 for the gory details)

On Hornady factory ammo it's sitting exactly where I'd expect a 20" barrel to be (80-100fps less than the published 24" data).

But following the recommended load ladder on Hornady's bolt gun data (with 31.2gr LVR max) I'm pushing velocities that indicate those loads are way over pressured, to the tune of some 80K PSI, and 31.2gr is tickling almost 2900fps out of a 20" barrel, seated to factory ammo measurements both with Hornady and Alpha brass (both have ~34.5gr H20 volume weight).

It might just be my lot of LVR has a ~4% burn rate increase which would explain the numbers I'm seeing but FYI as a data point for the Hornady folks, that upper bound for the LVR data in the Hornady book might be entirely too high, unless I'm messing something up.

 

[Ledzep]

So something to keep in mind as a general note. May or may not be the cause of what you're seeing.. Ball powders in the burn range of LVR are typically used in old lever action cartridges. Stuff like .30-30, .32-20, etc. In the case of LVR, the factory that makes the powder, when they start a new lot, they test it in a reference cartridge with a standard charge and bullet and the powder has to perform within certain parameters to be "in spec" to be "LeverEvolution". So if you took a bunch of lots of LVR and shot them in .30-30's with 150gr RN bullets you'd probably get very similar results amongst the lots.

However, something we've seen is that when you significantly change the operating pressure, bore diameter, bullet weight, etc... you can skew the performance variation of individual lots of "the same" powder. To correct for this, we've supplied 6mm ARC test equipment to the factory that produces the powder that goes in the factory ARC ammo and made it the reference cartridge/load for them to keep it consistent for that specific application. I have also seen variation in this powder in the 6mm ARC from various lots of powder. We don't "lawyer load" anything, it was run up to pressure in a clean SAAMI min-spec chamber test barrel with the lot of powder we had on hand at the time. We don't get enough cannister grade stuff in to know whether that lot is on the hot or slow side. Your lot(s) and components may or may not exactly replicate that performance.

TLDR: Lot-to-lot variation exits in all reloading components, start low and work up. Velocity matching isn't a perfect gauge but it's probably the closest thing that the individual reloader has so if you're way over book data (barrel length corrected), you might back off on charge weight a bit.

 

[CollarChoke]

So something to keep in mind as a general note. May or may not be the cause of what you're seeing.. Ball powders in the burn range of LVR are typically used in old lever action cartridges. Stuff like .30-30, .32-20, etc. In the case of LVR, the factory that makes the powder, when they start a new lot, they test it in a reference cartridge with a standard charge and bullet and the powder has to perform within certain parameters to be "in spec" to be "LeverEvolution". So if you took a bunch of lots of LVR and shot them in .30-30's with 150gr RN bullets you'd probably get very similar results amongst the lots.

However, something we've seen is that when you significantly change the operating pressure, bore diameter, bullet weight, etc... you can skew the performance variation of individual lots of "the same" powder. To correct for this, we've supplied 6mm ARC test equipment to the factory that produces the powder that goes in the factory ARC ammo and made it the reference cartridge/load for them to keep it consistent for that specific application. I have also seen variation in this powder in the 6mm ARC from various lots of powder. We don't "lawyer load" anything, it was run up to pressure in a clean SAAMI min-spec chamber test barrel with the lot of powder we had on hand at the time. We don't get enough cannister grade stuff in to know whether that lot is on the hot or slow side. Your lot(s) and components may or may not exactly replicate that performance.

TLDR: Lot-to-lot variation exits in all reloading components, start low and work up. Velocity matching isn't a perfect gauge but it's probably the closest thing that the individual reloader has so if you're way over book data (barrel length corrected), you might back off on charge weight a bit.

Yes sir that's exactly what I'm doing now, stepped it back until actual velocities match expected velocities at safe pressure ranges

Considering Hornady factory ammo tracks exactly to what I would expect to see, but my reloads with Hornady brass and 108gr eld-m bullets loaded to same CBTO as Factory 6ARC 108gr eld-m with LVR run hot, I reckon it's either my powder or my primer, or both.

~4% burn rate variance to the hot side on my LVR lot seems a reasonable explanation (and probably some primer variance as well + temperature sensitivity) but figured it was an interesting data point/observation.

 

[skyrep]

Recommend trying H4895. I've very good results with it for both the 103 & 108 bullets. For me, LVR to temp sensitive.

 

[Mr. Wolf]

Beautiful set up. What barrel (length, twist, maker) and what speed are you getting out of H4895?

Thank s

 

[skyrep]

Beautiful set up. What barrel (length, twist, maker) and what speed are you getting out of H4895?

Thank s

I built an 6mm ARC Bolt Action out of a Savage Model 10 GRS 6.5 Creedmoor back in 2021. At that time Shaw barrels had a special run for the 6mm ARC. I ordered - the Shaw 24” Savage Heavy Contour, 1-7” Twist, 5/8-24 Muzzle threaded, finished headspace , ready to install barrel and changed out the Bolt face to a PTG PPC Bolt Face. It now has over 800 rounds thru it and am more than Happy with the barrel.
It shoots great and have completed all my load development with it. Now I’ve started an AR configuration.

I tested a bunch of powder combination to see what the barrel liked. I found that my barrel really like a certain speed to get the best accuracy out of it:
90-95 grain bullets – IMR 8208XB4 - 2850 FPS / SD: 6.5

103 grain bullets – AR-Comp – 2790 fps / SD 9.3

105 grain bullets – AR-Comp – 2757 fps / SD: 4.8 or H4895 – 2768 fps / SD: 8.7

108 grain bullets – H4895 – 2763 fps / SD: 2.4

 

[JAS-SH]

I've been shooting the factory 6 ARC 108s for a number of years. In Florida I shoot in the 60's and 70's in the winter and high 80's to low 90's in summer. The temperature instability is there but not as bad as variations in powder charge.

My 6 ARC (see below) with a 26-inch barrel averages 2750's in the summer an 2740's in the winter. However, I do occasionally (say 1 shot per box) get a shot in the 2690's, but that happens at all temperatures. Best guess is that with small case capacities a few grains left out from a case by the automated production process this is expected. That all said, I did get one case lot that was all in the 2690s.

Here's the rifle - damn thing shoots! A 40-round target in 3-shot groups (with one Fup!) is below as well - the red grid on the target is made up of .25-inch squares.

 

[46caliber]

I get 2750 with Hornady 105, Starline, CCI #41 and W748 out of 25" and I've got some headroom. With slower burning powder like BL-(C)2 or CFE223, and a 26" it would be no problem. Shouldn't be a problem with StaBall Match either.

Just in case you didn't already know, a number of our ballistic solvers have a "temp table" function so you can input different velocities at different temperatures. As long as you then provide good atmospheric inputs when you shoot, the ballistic solver will take into account the varying speed with temp change.

All that said, I don't think I'll do the Hornady 105 BTHP beyond this box. Ogive is such that they must be loaded pretty short on a SAAMI spec chamber. I'll move to a sleeker bullet ala 107 SMK or ELD-M that can be seated longer without contacting lands.

Don't waste your time trying to figure out what powder Hornady is using. It's bulk commercial powder, not retail canister powder. I've connected with a few people that shoot a lot of 6ARC in PRS, both gas and bolt. N540 and CFE223 are the most commonly used propellants at least amongst those I've talked to.

 

[46caliber]

Load w/ 105 BTHP and Win748.