AR Comp & 105s

[StoneHendge]

Has anyone tried this combo? I've got enough of a lot left from another project for around 20 rounds in the mid 20s and was thinking of doing a ladder in case it pops up on the market again. Burn speed and density make it seem like it should work pretty well and maybe give the best velocities for a stick powder like it does in Grendel. My gut says around 26 grains would be the spot to cap it on a first try, but the only thing less scientific than my gut is the CDC. Was hoping to do 3 shots per charge 0.3 gr apart to get a reasonable idea of accuracy and SDs, which would be a ladder from about 24 to 26.....

[grayfox]

My grt estimates a max of 26.8 for the hornady 105, 22" barrel 2621 ft/s, est pressure 51600.
Usual disclaimers about different lot#s, different barrels, model estimate vs reality, etc.
But might be worth looking at.
AR comp is supposed to be a bit faster than RE15 but in that ballpark.

[StoneHendge]

Thanks gf!  That looks like it might give a few more fps than Varget, and yeah, Its somewhere in that slightly faster burn rate than Varget ball park. My 105 Match Burners are supposedly showing up today so I'll give it a whirl with them. I think I'll run from 24.5 to 26.5 since I'm base sizing these days. I can't think of a better way to get rid of one of those really annoying almost empty powder containers.

[StoneHendge]

Density appears to be near perfect - this is 26.5 grains in a base sized Starline converted Grendel case.

   

Bullet is a 105 Match Burner seated at 2.26" / 0.03" off of lands with the shank just hitting the bottom of the neck at that depth.

We'll see when i get to them since the weather in Phoenix is horrible - mid 50's, clouds and an occasional rain shower.

[CZ527 Guy]

Not many propellants I am looking to buy though this Power pro 2000 is on my shopping list I would really like to give her a go. Am I not looking hard enough or has this propellant been scarce.

[popgun]

Anxious to see the results. I just picked up 2# of AR-Comp and was looking for data.

[StoneHendge]

Not many propellants I am looking to buy though this Power pro 2000 is on my shopping list I would really like to give her a go. Am I not looking hard enough or has this propellant been scarce.

It's been scarce and wasn't around for quite some time, but a bunch showed up a couple of months ago. Its made in Sweden and with them relatively open, hopefully we'll see more. Its the best stick powder for 123s in Grendel, so if it looks like it might work here, it could be an option if it pops up again. I'm truly sick of being stingy with and  fighting to find ADI powders. I recently didn't buy something completely unrelated to reloading because it was from Australia.

[r.tenorio671]

...IIRC, Mr. Robert Whitley, developer of the 6mmAR . posted here in the forum somewhere about the powders he found to work well with the 6mm AR. AR-Comp/RL15 were included in that list.

...in the info Berger responded to my inquiry on their 105 & 95 grn bullets, they sent back a QL listing that included AR-Comp...the 105's max only reached ~2400 FPS and the 95's ~2550 FPS (PDF file included in my previous post). I've read posts in other forums/FB where folks have used it successfully with various FPS levels achieved. IIRC, it seemed better results were occurring with projectiles in the 90's class.

...like any component to be used, others findings give a reference point but the only way to determine the suitability for your individual use is testing in your platform & environment.

Edited: FWIW, the majority of folks using it were doing so because they were looking for powders that weren't affected by temperature swings. Many reports also indicated high levels of accuracy were also achieved.

[StoneHendge]

I braved the winter weather (60 degrees and clouds) and had some quite encouraging results today.

For a baseline, barrel is a 16" Lilja and I've been doing 26.5 gr of Varget in base sized Starline converted Grendel brass with 105 gr RDFs at 2430. When I was sizing with a Hornady die, I used 26.8 gr for 2445.

AR Comp loads are 3x Starline base sized,  BR-4, 105 gr Barnes Match Burner ata COAL of 2.26 / BTO 1.71 which is 0.03" off lands. This is the first time I've shot the MBs so I have no idea if they like a big jump like some lower BC bullets do (their 6.5 120s do like a big jump). Charges dropped on a CM 1500 using a faster technique than I would use for match ammo. SDs could be reduced through more care. Temp was 61 degrees. 3 shots per charge.

Charge /Velocity / SD / ES

24.0  2368 (1 only)
24.3. 2372. (1 only)
24.6. 2390 / 11/20
24.9. 2430/12/24
25.3. 2456/9/18
25.6. 2475/15/30  (2458, 2488, 2481)
25.9. 2518/16/30. (2510, 2507, 2537)
26.2. 2546/5/10
26.5. 2561/5/10
26.8. 2588 (1 only)

Nothing worse than MOA for accuracy and a sub 0.25  group at 25.6 and about 0.4 at 26.5. Something's giving me trouble posting a pic so I'll post separately. Note that they were through 10x on a Viper HSLR. Those aiming points are small compared to what they are like at 36x through my shiny new XRS3 on my CM or 21x through my shiny new DMR3 on my Grendel. I shot everything up to 25.6 today first, and then shot the rest after a string with my CM at 36x. 

Ejector marks at 26.2 gr which were more pronounced at 26.5. This could always be timing with my MLGS. Primers looked fine but things were feeling a bit warm near the end. I decapped when I got home to check the pockets. I've been losing about 15% at 4x. I think the results were quite telling: 26.8 was shot, 2 each of 3 were shot from 25.9 through 26.5. All of them were fine from 24.9 through 25.6.

Mid 25s is where I'd poke around if I had more powder and I'd consider 25.6 my max. As always, YMMV, but I'm guessing AR Comp is probably a winner among stick powders.

---

It let me attach separately. The top left which says 24.3 is actually 25.6. That one's under 0.25" and the 26.5 is about 0.4"

   

[popgun]

That's great! If I have similar results with pressure signs and charge weights that should get velocities in the upper 2600's to 2700 fps with a 22" barrel. Thanks!

[StoneHendge]

That's great! If I have similar results with pressure signs and charge weights that should get velocities in the upper 2600's to 2700 fps with a 22" barrel. Thanks!

If I was to extrapolate MY barrel to 22", I think I'd be looking at the low 2600s. I consider the 2 out of 3 loose pockets to be a pressure sign compared to the 15% I've been losing with a just off max charge of Varget.

[popgun]

I was just making a guess off of Hornadys data and your velocities at 25.6. 16" to 22" shows about a 190fps increase.

[popgun]

You was correct StoneHedge.
25.0 2591 SD 7 ES 15 1"
25.3 2612 14 25 .5" with two in one hole
25.6 2626 8 15 .7"
These were only 3 shot groups. Very light ejector marks in highest load. Also worth noting, my bolt did not lock back on last round with any of these. Vltor A5 buffer with one tungsten weight H1.
Hornady 105 BTHP, 22" gas gun

[shooter545]

Good stuff guys! I have 10lbs of AR Comp, both Hornady and Nosler 105s to try.

Thanks for the info and work ups.