My gas gun load development

[Burt Gummer]

Hey Folks

    I’ve been pretty hard at work scavenging a bunch of components since late 21 and have finally put enough of my own rounds down range to post my results with some confidence. First things first. 

Barrel: CLE 18” Criterion
Upper: Vltor Mur
Lower: Aero M4E1
Trigger: TriggerTech Diamond
Bolt: JP Enterprises Enhanced 6.5 Grendel 
Stock: MDT SCS (skeleton carbine stock)
Scope: Crimson Trace 6-24x Hardline Pro

    To start I ordered hundreds of Hornady 108 Match and and 105 Black to not only shoot for fun but to harvest the brass. Both of them shot terribly in my barrel and would normally be 1.5-2 MOA which is exactly my luck. Velocity was better than expected at an average of 2609 fps with the 108’s and 2669 fps with the 105’s. I was simultaneously getting into reloading for this reason since I don’t expect to see other Manufacturers jumping in anytime soon. 

    After sighting in the scope with factory rounds and collecting brass it took some time but I collected enough Lever, CFE223, Accurate 2520, and Winchester 748 to start my load development. I wanted to start off using the Barnes 112 gr Matchburner because the price as well as the BC’s were just too good to ignore. Not to mention they’re always available! 

    A few weeks ago I took a batch of my loaded 112’s to the range. The best loads with each of the following powders were as follows on a 77 degree day and 5 shots per group:

LEVR: 28 gr @ 2500 fps = 1.04 MOA

CFE223: 27.8 gr @ 2463 fps = .86 MOA

A2520: 27.8 gr @ 2505 fps = .89 MOA

WIN 748: 27.3 gr @ 2493 = .75 MOA

    In my opinion the results aren’t spectacular but not terrible. I was shooting for .75 MOA as the minimum accuracy I wanted to achieve in order to have a long range steel plinker. I wanted to see just how capable this barrel could be and tried something new.

    My brass is in the tumbler as I type from my range time today. I was confirming the accuracy node with the 748 and 112 Matchburners which went well but the main reason for making the trip out was to see if Berger 109 Hybrids could live up to their reputation. I’m still trying different powder charges with the bergers so I can’t speak to which is the best loads yet but here’s the results I’m comfortable with sharing:

LEVR: 28 gr @ 2528 fps = .89 MOA

Win 748: 27.1 gr @ 2520 fps = .5 MOA

    I couldn’t wipe the grin off my face after realizing I had a .5 MOA gas gun with just a little tinkering and experimenting with components! Leaning heavily towards the 748 now. I also feel that 748 doesn’t get enough exposure with the 6 ARC but I can tell you in my case it can’t be beat. My LabRadar missed 3/5 shots so I’m extrapolating from other data to come up with the velocity stated above but with the Barnes 112’s my ES was 12 with SD’s of 4. Hope this was informative for you guys and just wanted to contribute something to the community.

[grayfox]

Welcome aboard and to the great sport of reloading!!!
I have my fave Arc, is a 22" bolt one, but recently got an 18" gasser and am trying to relate to it. So this post is timely for me.
As rule in my other barrels I have tended towards 20, 22, or 24, not much of 18... but you know, perhaps the 18 is the ticket in the 6Arc.
I'm thinking that in general, if you can get into the 2525-2550 range with the right bullet wt, you'll have a node. I think I might see one in mine with 2585 and the 103 Eldx, but still experimenting. (my reasons are primarily for hunting). So I'm looking with the 90 Tgk and 103 eldx. Roger on the 112's line of thinking, but I haven't gone that high in weight...

[CZ527 Guy]

Welcome to the forum Burt

Never gave 748 serious consideration. Thanks for sharing.

Grayfox, If you are considering the 90 GR TGK May I suggest you consider the Nosler 90 GR BT. While Im not quite a fan of the hunting bullets that offer the massive energy dump primarily due to the potential lead in the meat. Still I gave the 90 GR BT (factory seconds) a try & was surprised how easy it was to find a accurate load in my bolt gun. Your milage may vary.

[Burt Gummer]

Welcome aboard and to the great sport of reloading!!!
I have my fave Arc, is a 22" bolt one, but recently got an 18" gasser and am trying to relate to it.  So this post is timely for me.
As rule in my other barrels I have tended towards 20, 22, or 24, not much of 18... but you know, perhaps the 18 is the ticket in the 6Arc.
I'm thinking that in general, if you can get into the 2525-2550 range with the right bullet wt, you'll have a node.  I think I might see one in mine with 2585 and the 103 Eldx, but still experimenting.  (my reasons are primarily for hunting).  So I'm looking with the 90 Tgk and 103 eldx.  Roger on the 112's line of thinking, but I haven't gone that high in weight...

We’re playing slightly different games but this cartridge works well in both. I don’t do much hunting but have on occasion so I picked up some Sierra 100 gr TGK to develop a load with. I believe I will see a velocity of  around 2720 fps with bullets in that weight range but haven’t had time to confirm yet. Should make an effective small to medium game cartridge in a small package.

[BluntForceTrauma]

Velocities looking good for an 18". Thanks for the report!

[Thelaststraw]

The 112 match burners are probably the best bang for the buck 6mm bullet out there today. Most important is availability just like you stated. I ran them a little in my gasser but they really come to life in a bolt rig at 28-2900.

The 105 BTHP Hornady bullets are very inconsistent but very forgiving in my experience as far as seating depth and jump....if you can look past the kooky OAL of finished rounds. I don't know for certain if that will work in a gas gun with mag restrictions (the widely varying OAL). They are cheap and plentiful too.

[Dino11]

105, 108, and 109 I run them at 29.4 of lever. I think you will get the results you seek pushing them a little harder. But work your load up to those levels.

I was also using Hornady brass, that stuff is tough.

[Burt Gummer]

The 112 match burners are probably the best bang for the buck 6mm bullet out there today. Most important is availability just like you stated. I ran them a little in my gasser but they really come to life in a bolt rig at 28-2900.

The 105 BTHP Hornady bullets are very inconsistent but very forgiving in my experience as far as seating depth and jump....if you can look past the kooky OAL of finished rounds. I don't know for certain if that will work in a gas gun with mag restrictions (the widely varying OAL). They are cheap and plentiful too.

Thanks for the advice. I haven’t gotten around to trying the Hornady 105’s even though I have 100 of them. My goal is long range shooting and the way the bergers and Barnes have performed so far I don’t have much interest in them yet. The Barnes easily fit into my steel ACIS and Duramags.

---

105, 108, and 109 I run them at 29.4 of lever. I think you will get the results you seek pushing them a little harder. But work your load up to those levels.

I was also using Hornady brass, that stuff is tough.

Thanks for the reply Dino. I have already tried testing both brands of bullets at the max charge weights for CFE223, Lever, and A2520 but my barrel doesn’t seem to like those powders as much. I think it’s trying to tell me to stay in the low 2500 fps range. Wish this wasn’t the case as I had jumped the gun and put all my marbles in LVR and picked up 3 lbs! Looks like I’ll have plenty of fire forming powder ?

[Dino11]

Lever and CFE should be your go to powders. Somethings got to be going on if your barrel does not like those two.

2500 is a little on the slow side, generally somewhere around 2650 seems like a sweet spot for accuracy with the 6 ARC. I have tested reloads with no less than eight different rifles and most if not all liked Lever, CFE, BL-C2, H335. I have used other powders with mediocre success but the aforementioned worked very well.

Really no need to fireform your brass if you are converting Grendel brass. I have fireformed and not fireformed with little to no difference between the two methods.

[Burt Gummer]

Lever and CFE should be your go to powders. Somethings got to be going on if your barrel does not like those two.

2500 is a little on the slow side, generally somewhere around 2650 seems like a sweet spot for accuracy with the 6 ARC. I have tested reloads with no less than eight different rifles and most if not all liked Lever, CFE, BL-C2, H335. I have used other powders with mediocre success but the aforementioned worked very well.

Really no need to fireform your brass if you are converting Grendel brass. I have fireformed and not fireformed with little to no difference between the two methods.

   Iagree with everything you’re saying regarding LVR and CFE. It was quite the surprise for me when both of them could barely manage sub MOA. 

   I’m also new to reloading and think this may have something to do with my results. I’ve already caught myself not bumping the shoulder back enough and causing cycling issues. One or two other steps could use a little more consistency admittedly. There’s a good chance that I could see better results with them but at this time with the short supply of components I think I’m going to stick with the 748 since it’s easy enough for a rookie like myself to get good results with. I ran two ladder tests with both the 112 Barnes and 109 Bergers using LVR and the results didn’t seem to change by much. ??‍♂️

[Dino11]

Are you annealing your brass, and checking neck size for bullet tension?

Those two things will effect your accuracy in a huge way. Plus you need to remember you are shooting a gas gun, but you do have a pretty good barrel.

What's the rate of twist on it, and how many rounds down the tube?

[Burt Gummer]

Are you annealing your brass, and checking neck size for bullet tension?

Those two things will effect your accuracy in a huge way. Plus you need to remember you are shooting a gas gun, but you do have a pretty good barrel.

What's the rate of twist on it, and how many rounds down the tube?

I anneal every other firing using 750 degree tempilaq as a guide. A Mighty Armory FL die for sizing with provided expander mandrel. I don’t check neck tension since I don’t have the tools to do anything about it. 

The inconsistencies I was referring to in the above post when bumping the shoulder, I get swings by as much as .003”. This causes me to have to run cases through three or four times and shrinking the shoulder slightly more each time so that they are all within .0005-.0001”. I know this isn’t normal and the research I have done indicates I’m not using enough lube on the cases (Dillon lube) and it’s causing too much friction thus throwing the sizes off. I haven’t had any fired brass to try this out on yet. Any thoughts?

[IALoder]

105, 108, and 109 I run them at 29.4 of lever. I think you will get the results you seek pushing them a little harder. But work your load up to those levels.

I was also using Hornady brass, that stuff is tough.

105 hybrids, 105 match burners, and 108 ELDM's have all dialed in between 29.2-29.6gr in my rifle.  I think that's a pretty standard loading spot for the 6 ARC with 105's and 108's.  Like Dino11 said, maybe you need to push them a little harder!

[Burt Gummer]

105, 108, and 109 I run them at 29.4 of lever. I think you will get the results you seek pushing them a little harder. But work your load up to those levels.

I was also using Hornady brass, that stuff is tough.

105 hybrids, 105 match burners, and 108 ELDM's have all dialed in between 29.2-29.6gr in my rifle.  I think that's a pretty standard loading spot for the 6 ARC with 105's and 108's.  Like Dino11 said, maybe you need to push them a little harder!

I’m starting to hear the message. I’ll make trying out the 108 ELD’s a bigger priority. I’m heading to the range this weekend to more or less confirm the accuracy of the best loads so far. Have to then turn around and go through a long range qualification course at the end of this month that will eat up more of my shooting and reloading time. Going to stick with a proven load for that. I’ll try to report back with results on the 108’s and possibly 105’s over the next month or two. The B.C’s are a little disappointing coming from the Barnes and Bergers but if they can offer some advantages in accuracy or velocity they might just be worth it. Appreciate all the feedback.

[Burt Gummer]

Interesting range session today. The goal was to simply confirm that the Win 748 27.1 gr charge was going to be my most accurate charge weight and double check ES and SD’s. I snuck in a couple other CFE and LVR loads that I wanted to test all within similar velocity ranges as the 748 powder. I alternated between using Berger 109’s and the Barnes 112 Matchburners with different powder weights as well as mainly testing with once fired Starline 6.5 Grendel brass sized down to ARC. First big batch of Starline brass I have worked with.

The weather was clears skies and around 56 degrees which is also the biggest drop in temperature since honing this load in and I wanted to see how much it would throw my results off. It was quite warmer at 72 and 88 degrees the first couple of times I was looking into it. I can indeed report that the Win 748 at 27.1 gr was still by far the most accurate powder weight and favored powder for my Criterion barrel. The CFE and LEVR once again crapped the bed with .76 MOA being the best for CFE. LVR was over MOA. Both with Bergers.

The weirdest part for me is in the complete reversal of the Bergers being the most accurate when it came time to put them toe to toe with the Burners. The Matchburners blew the doors off of the Bergers. Best the Bergers could muster with 748 and five shots of the 27.1 gr loads was .65 MOA group. The 112’s dominated that with a .39” group! Same 27.1 gr load. Both with Star brass.

Here’s the downside. The limitations of having a temperature sensitive powder on top of my accuracy node being on the lower end of acceptable became clear today. Shooting at around 56 degrees Fahrenheit dragged my average velocity down to 2471 for the Bergers and 2458 for the Burners. This is still acceptable for me and for the games I plan to play. I’ll just have to work the scope dials a little longer than some. I’ll be sticking with the 27.1 for my upcoming long range course at the end of the month just because I need a proven load. There’s a qualification at the end that I don’t want to fail and this rig should be more than capable of the 600 yard distance we’ll be shooting. I’ll start testing LEVR and CFE some more when I finish the next batch of hand loads. 

I’ll obviously have to test out the mystery behind my Bergers being bested by the Burners. This is the first time I’ve shot them back to back on the same day with the same powder and brass. The other detail I haven’t mentioned is that I sorted the Barnes bullets about a week ago. Okay, not all of them but enough to take to the range! Who’s got time for that? My next range trip I can squeeze in for testing hand loads I’ll be trying to figure that out. Was it the change in Brass or sorting the base to ogive of each one of the Barnes Bullets? Maybe they were pulled into a beetle accuracy node with the slower fps and it’s neither of the first two options. Cliffhanger. All I can say is that I understand now why reloading doesn’t save anyone money! ?

[Burt Gummer]

Also forgot to mention. For the two best loads mentioned the Bergers had an ES of 26 with SD of 13. Burners had ES = 18 and SD = 9.

[GRH]

It seems I overlooked W748 when choosing a powder. I tried TAC, Varget and A2520 and settled on A2520, and coincidentally came up with 27.16gr pushing 108ELD-M avg 2471fps, sd 6.5 es 15 from a 20" BA premium 1-7 barrel.

Using my calibrated GRT model, a quick look at W748 appears to show that the two are near identical with W748 being just a bit faster and higher pressure. Where A2520 burns after passage at 97.8%, W748 burns 100% with burnout just before muzzle.

[Dino11]

I just recently ran some loads with W748 topped off with some 100 gn Speer soft point boat tails. These were pulled bullets I got from American Reloading and the points on some of them were flattened because they pulled them wrong.

I did not load these for anything special, mostly to fireform some brass. But was some what surprised at the level of accuracy with them running a light load. I did not chrono them but they were hitting point of aim consistantly once the scope was dialed in for them. And it did burn clean and the cases would eject and you could pick them up and they were actually pretty cool, and the barrel didn't heat up as well.

Maybe I should try a load development using some good 90 to 100 gn bullets, I know velocity will be down with this powder but if it performs accurately it might be worth using since I have about 9 or 10 lbs of the stuff.

[Burt Gummer]

It seems I overlooked W748 when choosing a powder. I tried TAC, Varget and A2520 and settled on A2520, and coincidentally came up with 27.16gr pushing 108ELD-M avg 2471fps, sd 6.5 es 15 from a 20" BA premium 1-7 barrel.

Using my calibrated GRT model, a quick look at W748 appears to show that the two are near identical with W748 being just a bit faster and higher pressure. Where A2520 burns after passage at 97.8%, W748 burns 100% with burnout just before muzzle.

Valuable burn rate info right there. I didn’t realize the two powders were that close. Who would’ve thought such a small difference could be so significant in the same barrel.

[Burt Gummer]

I just recently ran some loads with W748 topped off with some 100 gn Speer soft point boat tails. These were pulled bullets I got from American Reloading and the points on some of them were flattened because they pulled them wrong.

I did not load these for anything special, mostly to fireform some brass. But was some what surprised at the level of accuracy with them running a light load. I did not chrono them but they were hitting point of aim consistantly once the scope was dialed in for them. And it did burn clean and the cases would eject and you could pick them up and they were actually pretty cool, and the barrel didn't heat up as well.

Maybe I should try a load development using some good 90 to 100 gn bullets, I know velocity will be down with this powder but if it performs accurately it might be worth using since I have about 9 or 10 lbs of the stuff.

Good to hear. Hopefully the Sierra 100 gr bullets I picked up will like it just as much. It’s not going to give you the LVR velocity but it seems like it might be a great alternative. Even for what I’m doing the 2458 fps paired with a extremely high BC bullet is an easy 1000 yard round in an 18” package. That just seems too cool to be real so happy to use it if it’s the only powder I can shoot at or under .5 MOA with. Not giving up on LVR quite yet but time for this hobby is limited.