New 6mm Advanced Rifle Cartridge

[Yondering]

Some food for thought about necking down Lapua Grendel brass for the 6mm ARC:

- All of the Lapua brass I've bought for the Grendel is .010" to .020" short of a minimum spec Grendel or LBC chamber at the shoulder datum. This is typical of most brass and loaded ammo, and is not specific to the Grendel or just Lapua. (I think most people don't realize how much headspace most factory ammo actually creates.)
- The 6mm ARC is .030" short of a Grendel chamber at the shoulder datum.

Sizing this brass down to the 6mm ARC means you're only barely bumping the shoulder back, just .010" to .020", and can give you that ideal .002-.004" shoulder bump right from the start, rather than new ARC brass which is likely to be short just like Grendel brass (and pretty much all factory ammo and brass for most cartridges).

IMO this is a good thing that knowledgeable ARC shooters should take advantage of.

 

[Yondering]

aww man. that all sounds pretty good advise, thx will post results.
I think that does answer a question I have, or bring it up for discussion anyway.

If it is overgassed, and I adjust as to vent more of the gas out of the block, would that not take away from the gas that pushes the bullet out of the barrel from the gas block to the end of the barrel? Perhaps I could MAKE UP for that vented gas, by increasing the powder charge overall?

Also the SA block is able to vent gas forward of the block to free air OR direct it down the tube to the bolt. Which one is most advantageous for my setup (Muzzle break/no supressor) - looking for higher velocities with some value toward follow up shots and reliability/functionality.

It seems like the following are true, please schl newb as needed or point me to other threads that may explain in detail:

• The best velocity would be fully closed gas block, sending all the power directly to the bullet - This would be overgassed and beat on the action/brass and would not provide "ideal" recoil impulse for follow ups.
• The softest shooting recoil impulse would be venting just enough gas to run the bolt, but that vented gas would lower vel.
• The best reliability would be to adjust a tad more gas than holds for last round hold open(as they describe in instructions/setup), but that would not be ideal for velocity OR follow up shots/soft shooting
• The ideal Gas Block setting is some magical number in the middle.

If you want my opinion - the bleed off function of the SA gas block is stupid, and always has been. It's a triumph of marketing rather than engineering.

My suggestion is to use it in gas restriction mode, like other adjustable gas blocks. Fortunately you can do that, and that mode has a wider range of adjustment anyway.

Forget about velocity when you're adjusting the gas block. It doesn't make any significant difference* and is the kind of minutia of detail that isn't worth considering. Adjust the block for correct function of the rifle with the load you want to use, and then determine your velocity for that load after the rifle is working right. If you use a stick powder, you'll probably need less restriction, and if you use Lever, you'll need more restriction.

*During one of my 243 LBC builds (I turn my own barrels from blanks) I measured the velocity difference before and after drilling the gas port. With a max load of Lever and the 105gr BTHP, the difference between no gas port and slightly overgassed was 10 fps. The affects of different gas block adjustments are even smaller than that.

 

[newageroman]

Thanks for the info, I was thinking the vented gas would take away more velocity than that. I will tune it up and see how they roll.
I've never really used the bleed off function, I think that is more for supressors, I'm just trying to exhaust all tuning options.
I *almost got to try them over a lab radar today at 380y but reasons prevented it. oh well.

 

[jbailey]

Guys, especially those shooting the lighter bullets, this video has a good compare of Lever vs Varget. Both produced fantastic MVs for the barrel length (18") and bullet weight (90gr). The Lever load was a just under 3000fps (don't know what the temp). Precision and MV StDev also both excellent.



Looking at his brass at the end of the video, his Lever load is towards high end of pressure and I would be stopping based on those swipes on the brass.

 

[Henryrifle]

Just a post for fun…

I spent some time at the 1000 yard range yesterday and while I wasn’t planning on shooting the 6mm ARC, the rifle I wanted to shoot developed a trigger problem after several shots.

I pulled the 6mm ARC out of the truck with the idea [hope] of getting a cold barrel fist round hit on the 1.8 MOA steel target at 1000. Using a Kestrel Drop and Applied Ballistics app, I dialed in 35 MOA for the 108 ELD-M at 2662 FPS. The shot was high, way high, and, after two more adjustments, settled on 33 MOA suggesting a 2740 FPS MV. So, it took 4 shots to get on target—way to many…

I wasn’t measuring MV yesterday but the temperature was in the upper 60s where I’ve done all the load development for this load and, the ammo hadn’t been shut up in a hot truck. The doors were open all afternoon.

I have also experienced this issue before at 500 meters with the 6mm ARC where the app gives a solution that is about 1 MOA high. I am even using the custom drag model for this bullet. I did run a ballistic calibration yesterday and we’ll see if that makes a difference next time. Normally the combination of Kestrel data and Applied Ballistics gives a very good firing solution.

Once on target, the rifle shot great. Hits on steel were pleasantly consistent. Running suppressed, it was easy to hold the scope on target through recoil and spot hits and misses. I continue to be impressed that an AR-15 chambered in 6mm ARC is such a great all-around hunting and target rifle.

I am still using CFE 223 but will eventually get around to trying out LEVERevolution.

If you’re thinking about buying or putting one of these together, I think you’ll be happy that you did!

Henryrifle

 

[ormandj]

Guys, especially those shooting the lighter bullets, this video has a good compare of Lever vs Varget. Both produced fantastic MVs for the barrel length (18") and bullet weight (90gr). The Lever load was a just under 3000fps (don't know what the temp). Precision and MV StDev also both excellent.



Looking at his brass at the end of the video, his Lever load is towards high end of pressure and I would be stopping based on those swipes on the brass.

Just being a gas gun, and knowing pressure limitations (52kpsi) are below where you'd often see the typical brass signs, I'd be limiting my velocity to somewhat near book velocity, not limiting myself to max load in terms of charge weight (allowing for some variance due to bullet/barrel differences). I agree, I think he's probably over 52kpsi with those loads, but it's all conjecture. He's at 2965 fps for LVR 31.5gr, where on the 87gr vmax 31.6gr should be at ~2850. That's a pretty good margin above book data, so I would be reducing my charge. Varget 30.0gr he's at 2827 fps, 87gr vmax should be at 2750 for 29.7gr. That seems a little closer to the book data, but he's also probably over max pressure.

Either way, neat to see his loads shoot so well, there's nothing wrong with those groups when he's not really even playing with seating depth or shooting smaller increments. Thanks for posting, I always enjoy his videos!

 

[ormandj]

Just a post for fun…

I spent some time at the 1000 yard range yesterday and while I wasn’t planning on shooting the 6mm ARC, the rifle I wanted to shoot developed a trigger problem after several shots.

I pulled the 6mm ARC out of the truck with the idea [hope] of getting a cold barrel fist round hit on the 1.8 MOA steel target at 1000. Using a Kestrel Drop and Applied Ballistics app, I dialed in 35 MOA for the 108 ELD-M at 2662 FPS. The shot was high, way high, and, after two more adjustments, settled on 33 MOA suggesting a 2740 FPS MV. So, it took 4 shots to get on target—way to many…

I wasn’t measuring MV yesterday but the temperature was in the upper 60s where I’ve done all the load development for this load and, the ammo hadn’t been shut up in a hot truck. The doors were open all afternoon.

I have also experienced this issue before at 500 meters with the 6mm ARC where the app gives a solution that is about 1 MOA high. I am even using the custom drag model for this bullet. I did run a ballistic calibration yesterday and we’ll see if that makes a difference next time. Normally the combination of Kestrel data and Applied Ballistics gives a very good firing solution.

Once on target, the rifle shot great. Hits on steel were pleasantly consistent. Running suppressed, it was easy to hold the scope on target through recoil and spot hits and misses. I continue to be impressed that an AR-15 chambered in 6mm ARC is such a great all-around hunting and target rifle.

I am still using CFE 223 but will eventually get around to trying out LEVERevolution.

If you’re thinking about buying or putting one of these together, I think you’ll be happy that you did!

Henryrifle

Try Hornady 4DOF and use the 4DOF modeling since you're using Hornady bullets.

 

[lennyo3034]

Just got notification that my Craddock Bartlein barrel is ready.

Unfortunately bolt is still on backorder through JP....since July. Not looking like I’ll get this rifle up in 2020.

 

[ormandj]

Just got notification that my Craddock Bartlein barrel is ready.

Unfortunately bolt is still on backorder through JP....since July. Not looking like I’ll get this rifle up in 2020.

Why didn't you just grab a bolt through Craddock and have the barrel headspace to it? I sent in a bolt (Toolcraft) to do the same - but they also have bolts available. You can call them up and see if they have one they can sell you? It'll get you up and shooting, and honestly, if you're sticking to 52kpsi any good quality bolt will be fine, the JP isn't worth waiting half a year imo.

 

[lennyo3034]

Why didn't you just grab a bolt through Craddock and have the barrel headspace to it? I sent in a bolt (Toolcraft) to do the same - but they also have bolts available. You can call them up and see if they have one they can sell you? It'll get you up and shooting, and honestly, if you're sticking to 52kpsi any good quality bolt will be fine, the JP isn't worth waiting half a year imo.

I asked, they didn't have one. They have a JP they use for headspacing but nothing to sell.

 

[ormandj]

I asked, they didn't have one. They have a JP they use for headspacing but nothing to sell.

Damn. This insane buyings spree has got to end sometime, it's so hard to find anything anymore.

If you're not adverse to buying a full BCG: https://www.brownells.com/rifle-par...bolt-carrier-group-nitride-mp-prod105382.aspx

My guess is it's a Toolcraft BCG + bolt, which is GTG. JP talks a lot about their enhanced bolt, and I have no reason to doubt it's nice, but my Toolcraft DLC 6.5 BCGs have both been great, and have the radius edges on the bolt lugs. It's 9310 for the bolt and 8620 for the BCG. Not sure on all the other stuff the JPs talk about being important, I've not had any of that fail on my bolts.

Just took a picture (sorry for the blur, just a hurried cell phone picture) of one of my bolts; it's a bit dirty right now as I haven't cleaned in a few hundred rounds. You could call Brownells and see if their OEM is Toolcraft.

 

[tomcatfan]

I finally got my 21" Odinworks 6ARC build out to 1000 yds today and I was very impressed. Compared to my 6.5CM AR-10, it had surprisingly similar ballistics between a 140 eld and the 108 eld. The 6ARC of course was lighter recoiling. I had no problems getting hits on an 100% IPSC target with the rifle.

I wanted a 6.5 CM AR-10 to shoot 1000 yds, and honestly the 6ARC makes my AR-10 obsolete. What a cool round. I can't wait to get home to my reloading set up and see what I can do with handloads.

 

[Rumblestrip]

Just being a gas gun, and knowing pressure limitations (52kpsi) are below where you'd often see the typical brass signs, I'd be limiting my velocity to somewhat near book velocity, not limiting myself to max load in terms of charge weight (allowing for some variance due to bullet/barrel differences). I agree, I think he's probably over 52kpsi with those loads, but it's all conjecture. He's at 2965 fps for LVR 31.5gr, where on the 87gr vmax 31.6gr should be at ~2850. That's a pretty good margin above book data, so I would be reducing my charge. Varget 30.0gr he's at 2827 fps, 87gr vmax should be at 2750 for 29.7gr. That seems a little closer to the book data, but he's also probably over max pressure.

Either way, neat to see his loads shoot so well, there's nothing wrong with those groups when he's not really even playing with seating depth or shooting smaller increments. Thanks for posting, I always enjoy his videos!

One thing to remember is that Hornady data tends to error on the conservative side when you compare with other published load data. Has anyone other than Hornady published official load data yet e.g. Speer, Berger, Lyman, etc,.

 

[ormandj]

One thing to remember is that Hornady data tends to error on the conservative side when you compare with other published load data. Has anyone other than Hornady published official load data yet e.g. Speer, Berger, Lyman, etc,.

I don't think it's conservative in terms of the 52kpsi limit. Their data may be conservative in a bolt gun, in terms of maximum loads you can run without having your rifle explode, but these loads seem to track the PSI max you want to target with this bolt in an AR!5.

Hodgdon has some data for a wide variety of bullets. Here's a small snippit from a 24" barrel (low then high charge/velocity/pressure):

110 GR. HDY A-TIP​

LVR​

.243"​

2.260"​

25.4​

2410​

38,600 PSI​

28.2C​

2660​

51,200 PSI​

110 GR. HDY A-TIP​

Varget​

.243"​

2.260"​

23.0​

2296​

38,600 PSI​

25.7C​

2541​

51,900 PSI​

You can compare that with the same loads in the Hornady PDF.

 

[LRBuck]

Just got notification that my Craddock Bartlein barrel is ready.

Unfortunately bolt is still on backorder through JP....since July. Not looking like I’ll get this rifle up in 2020.

When did you place your order with Craddock? Just curious since I ordered a rock creek barrel from them back in July and haven’t yet heard its coming.
Hate to hear that about your bolt being delayed. I would pull my hair to have the barrel but no bolt. Toolcraft bolts have worked well for me too in the past. It is how to get a good headspace to the barrel for best accuracy that I haven’t ever figured out. If anyone wants to share their expertise on that I sure would like to know.

 

[Dino11]

I have a Rubber City Armory BCG in one of my 6 ARC's. This is a very high quality BCG, The Nitrided finish on them is the best in the market, even the firing pin is Nitrided. Bolt is 9310 steel and radius ground. And it is adjustable. You would be hard pressed to find another BCG that is any better than one of these. Just don't use any solvent to clean it up, all it takes is a wipe down with a paper towel. Solvents destroy Nitrided finish. And as of this post they have two in stock. They are local to me so I just stop by and pick up from their factory, Jeff the owner is a pretty good stand up guy. He always hooks me up, the Grendel one I purchased I watched him personally build it from parts bins right in front of me.

https://rubbercityarmory.com/produc...ss-m16-profile-complete-w-adjustable-gas-key/

 

[ormandj]

When did you place your order with Craddock? Just curious since I ordered a rock creek barrel from them back in July and haven’t yet heard its coming.
Hate to hear that about your bolt being delayed. I would pull my hair to have the barrel but no bolt. Toolcraft bolts have worked well for me too in the past. It is how to get a good headspace to the barrel for best accuracy that I haven’t ever figured out. If anyone wants to share their expertise on that I sure would like to know.

Headspace is set when the extension is installed. You can't do it ex post facto.

 

[Constructor]

When did you place your order with Craddock? Just curious since I ordered a rock creek barrel from them back in July and haven’t yet heard its coming.
Hate to hear that about your bolt being delayed. I would pull my hair to have the barrel but no bolt. Toolcraft bolts have worked well for me too in the past. It is how to get a good headspace to the barrel for best accuracy that I haven’t ever figured out. If anyone wants to share their expertise on that I sure would like to know.

After the extension is installed there are 2 ways. Get a hand full of bolts and pick the one that makes the headspace closest to the go gauge or reload and size the brass .003-.004 smaller than the chamber size.

 

[ormandj]

After the extension is installed there are 2 ways. Get a hand full of bolts and pick the one that makes the headspace closest to the go gauge or reload and size the brass .003-.004 smaller than the chamber size.

That's fair, I suppose you can find a bolt that fits if you've got a bunch with varying sizes. Either way, the second piece of advise is excellent when it comes to reloading - I always aim for 0.003" (FL sizing, to be clear) sizing post-annealing for ar15s, and have had great success with no issues feeding. Just make sure to account for springback if you start cutting it closer, especially with non-annealed brass after a few firings/sizing operations.

 

[simplemank]

I have a Rubber City Armory BCG in one of my 6 ARC's. This is a very high quality BCG, The Nitrided finish on them is the best in the market, even the firing pin is Nitrided. Bolt is 9310 steel and radius ground. And it is adjustable. You would be hard pressed to find another BCG that is any better than one of these. Just don't use any solvent to clean it up, all it takes is a wipe down with a paper towel. Solvents destroy Nitrided finish. And as of this post they have two in stock. They are local to me so I just stop by and pick up from their factory, Jeff the owner is a pretty good stand up guy. He always hooks me up, the Grendel one I purchased I watched him personally build it from parts bins right in front of me.

https://rubbercityarmory.com/produc...ss-m16-profile-complete-w-adjustable-gas-key/

I would agree. Running the same bolt. Customer service has been outstanding from them for me also.

 

[ormandj]

Nitride finishes are not ruined by solvent. They will turn “pink” with the citric acid based cleaners like lemishine or anything like CLR. The surface treatment continues to work, however; it is not chemically removable.

 

[Yondering]

Solvents destroy Nitrided finish.

Wait, what?

Who told you that?

 

[Constructor]

Some chemicals will hurt Nitride finishes. Bullfrog Rust Hunter and the "green" brake cleaner seems like it was CRC brand. Of course they don't hurt the heat treat but do discolor the black.

 

[ormandj]

Nitride finishes are not ruined by solvent. They will turn “pink” with the citric acid based cleaners like lemishine or anything like CLR. The surface treatment continues to work, however; it is not chemically removable.

Some chemicals will hurt Nitride finishes. Bullfrog Rust Hunter and the "green" brake cleaner seems like it was CRC brand. Of course they don't hurt the heat treat but do discolor the black.

It's only cosmetic, so we are clear, because ruin/hurt/etc mean different things to different people. You'll get a pinkish hue if you use anything with a citric acid component, to include CLR. I don't know if the "Rubber City" BCGs are just nitrided or FNCd but either way, the surface properties should remain re: abrasion resistance, corrosion resistance, etc. I had a gentleman ask for help one day with a pistol he'd thrown in the ultrasonic to clean for an hour after processing some brass with ... lemi-shine. I should have taken pictures.

 

[Dino11]

Wait, what?

Who told you that?

The guy that does it for a living.

Jeff Larson the owner of Rubber City Arsenal.

 

[simplemank]

ASC now makes 6mmARC specific magazines

https://www.ammosc.com/categories/ar-15-magazines/6mm-arc.html

You had good luck with these mags?

 

[simplemank]

Curious if anyone has ran any AA2520 yet? Was thinking about trying some with the 107 Sierra.

 

[eugevita]

About to join the 6 ARC world!

Ordered a ballistic advantage 18" SPR profile 6 ARC barrel from brownells as well as a billet lower and 6.5 grendel ultimate upper kit from Larue! Plan to replace the Larue barrel with the ballistic advantage 6 ARC! Pretty pumped to get the parts and get this thing running!

Any advice? Also purchased 320 rounds of 108 ELD to start.

It sounds like folks are having good luck with the C products duramags from what I have read here?! If anyone has a line on solid 6 ARC mags that are on sale let me know! Appreciate any advice from the 6 ARC experts!

 

[Henryrifle]

@eugevita: I think you are going to enjoy your new rifle. Would be interested to know how you plan to use it. As I relate some of my experiences, my goals were to put together a relatively light weight platform that I could use for deer hunting AND one also capable of hitting steel at 1000 yards. As such, I have stayed focused on the heavier bullets and, most specifically, the 108 ELD-Match. I think the BA barrel is a 7 twist barrel meaning you can try the heaviest 6mm projectiles available. My current barrel, a Wilson, is 21.75" long with a 7.7 twist so, I may be capable of 20-40 FPS more than your barrel.

I started with Varget and H4895 and ran into pressure and ruined primer pockets early on only getting to about 2575 FPS. I could have made this work, however, several posters on this forum turned me on to CFE 223. I am now shooting the 108 ELD at 2660 +/- 5 FPS with no pressure and great brass life. This load shoots in the .7s at 100 yards, knocks down, on the spot, small to medium-small deer at 300 yards and easily impacts 1.8 MOA steel at 1000 yards.

It sounds like LEVERevolution is another great powder choice for this cartridge that I intend to try. It is hard to switch powders when you have something that is working...

I have used CCI 450, CCI BR4s and CCI 400 primers. All have worked flawlessly. I did not measure any muzzle velocity difference between CCI 450s and BR4s and, oddly enough, the CCI 400s increase velocity consistently by about 10 FPS. I have settled on the 400s to save the others for competition shooting while this shortage persists.

I have been loading the 108s at 2.255" using Hornady Custom Grade dies and did add the micrometer top to the seating die. The set comes the correct seating stem for the 108 ELD-M and 103 ELD-X bullet.

There are others shooting lighter bullets for varmint-style shooting that I know will weigh in to your question.

Let us know your plans for the rifle...

Henryrifle

 

[Flyinghunter]

6mm ARC question: Is anyone producing 12-12.5 inch barrels yet? And really reaching...a complete upper with that barrel length?

 

[eugevita]

@eugevita: I think you are going to enjoy your new rifle. Would be interested to know how you plan to use it. As I relate some of my experiences, my goals were to put together a relatively light weight platform that I could use for deer hunting AND one also capable of hitting steel at 1000 yards. As such, I have stayed focused on the heavier bullets and, most specifically, the 108 ELD-Match. I think the BA barrel is a 7 twist barrel meaning you can try the heaviest 6mm projectiles available. My current barrel, a Wilson, is 21.75" long with a 7.7 twist so, I may be capable of 20-40 FPS more than your barrel.

I started with Varget and H4895 and ran into pressure and ruined primer pockets early on only getting to about 2575 FPS. I could have made this work, however, several posters on this forum turned me on to CFE 223. I am now shooting the 108 ELD at 2660 +/- 5 FPS with no pressure and great brass life. This load shoots in the .7s at 100 yards, knocks down, on the spot, small to medium-small deer at 300 yards and easily impacts 1.8 MOA steel at 1000 yards.

It sounds like LEVERevolution is another great powder choice for this cartridge that I intend to try. It is hard to switch powders when you have something that is working...

I have used CCI 450, CCI BR4s and CCI 400 primers. All have worked flawlessly. I did not measure any muzzle velocity difference between CCI 450s and BR4s and, oddly enough, the CCI 400s increase velocity consistently by about 10 FPS. I have settled on the 400s to save the others for competition shooting while this shortage persists.

I have been loading the 108s at 2.255" using Hornady Custom Grade dies and did add the micrometer top to the seating die. The set comes the correct seating stem for the 108 ELD-M and 103 ELD-X bullet.

There are others shooting lighter bullets for varmint-style shooting that I know will weigh in to your question.

Let us know your plans for the rifle...

Henryrifle

Henryrifle, thank you for sharing, very useful info!

My primary use is the same as yours, a lightweight rifle that can get out to 1000 yards no problem and also be secondarily used to occasionally hunt whitetail deer and pigs here in NC! I plan to take my Leupold MKIV FFP 4.5-14x40 of my rem 700 308 and run it on this rifle. Essentially my goal is to have a SPR build on "light steroids" lol Pretty much an SPR that can shoot further and take some game!

Unfortunately I do not reload currently but might get into it down the line. As I mentioned I purchased 320 rounds of 108ELD to start and hopefully that will shoot well and remain somewhat available. Will also probably check out the hornady black ammo and see what the gun likes.

What mags do you recommend? And how critical do you think it will be for me to install the adjustable gas block?

Thanks bro!

 

[Silverjay]

I have a ballistics advantage barrel on a Larue 6.5 Grendel. Settled on a light weight carrier with a standard gas block. Runs well with and w/o a suppressor.

 

[SkyScrapin]

Anyone know where a guy can source a proof carbon 18” 6 arc barrel?

 

[LRRPF52]

Just being a gas gun, and knowing pressure limitations (52kpsi) are below where you'd often see the typical brass signs, I'd be limiting my velocity to somewhat near book velocity, not limiting myself to max load in terms of charge weight (allowing for some variance due to bullet/barrel differences). I agree, I think he's probably over 52kpsi with those loads, but it's all conjecture. He's at 2965 fps for LVR 31.5gr, where on the 87gr vmax 31.6gr should be at ~2850. That's a pretty good margin above book data, so I would be reducing my charge. Varget 30.0gr he's at 2827 fps, 87gr vmax should be at 2750 for 29.7gr. That seems a little closer to the book data, but he's also probably over max pressure.

Either way, neat to see his loads shoot so well, there's nothing wrong with those groups when he's not really even playing with seating depth or shooting smaller increments. Thanks for posting, I always enjoy his videos!

He was loading longer COL, which creates more case volume and less pressure of course. He should be loading in .3gr increments though, not .5gr. Is his longer COL enough to give him that much more room? I doubt increasing the COL from 2.260” to 2.297” is going to allow you 115fps more mv at the same pressure. How many more grains can .037” really give you in the case? I would expect to see maybe 40-50fps more mv, but not 115fps. So unless he has a barrel with shallow rifling, I also suspect the pressure is over 52,000psi, which isn’t going to show up on primers or case heads even in the slightest.

He’s getting 24” 6mm ARC velocities at 62,000psi with H335 pushing an 87gr V-MAX.
His velocities also match 24” Hornady data at 62,000psi with the 90gr GMX on top of H335, TAC, and Power Pro Varmint. The GMX has different start pressure considerations since it’s a solid though.

Even with the longer COL, there’s a very high likelihood that he might be over 62,000psi.

 

[Henryrifle]

What mags do you recommend? And how critical do you think it will be for me to install the adjustable gas block?

Thanks bro!

I have only used the E-Lander magazines because I had a few from the 6.5 Grendel project. They have worked great so far in spite of the suppresser making them extra dirty on the inside requiring some clean up from time to time.

Regarding the adjustable gas block, I have to be honest and say that I don't have much experience tuning ARs. We have neighbors that complain about shooting and, as a result, I try to soot everything suppressed. I have put AGBs on the few ARs I own to fix the over gassed condition caused by suppressor use but I know others can offer expert advice on that front. In short, I run AGBs because I have to.

You've got to get into reloading when components are available again. It will change your life -- well, you shooting life anyway!

Henryrifle

 

[SBRSarge]

6mm ARC question: Is anyone producing 12-12.5 inch barrels yet? And really reaching...a complete upper with that barrel length?

I almost bought a McGowen a week or two ago that was, I think 12.5. Not sure if they still have them.

I’m in the perpetual back-ordered holding pattern waiting for an Odin to become available so I ended up passing on the McGowen

 

[r.tenorio671]

Henry, your statements , re:

"It sounds like LEVERevolution is another great powder choice for this cartridge that I intend to try. It is hard to switch powders when you have something that is working...
I have used CCI 450, CCI BR4s and CCI 400 primers. All have worked flawlessly. I did not measure any muzzle velocity difference between CCI 450s and BR4s and, oddly enough, the CCI 400s increase velocity consistently by about 10 FPS. I have settled on the 400s to save the others for competition shooting while this shortage persists."

Are exactly why testing multiple components is viable, one never knows what will be available and when, having multiple loads will carry you over any shortages that may occur.

 

[Henryrifle]

Tested with some 107 Sierra MatchKings today. After deciding to go to the range late, I loaded 20 rounds of the 107 SMKs over what is working for me with the 108 ELD-Match bullets, 29 grains of CFE 223. The temperature was in the 62 to 66 degree range today where I have done almost all of the previous testing.

I shot four 5-shot groups with group sizes of .97, 1.02, .96 and 1.01 MOA at 100 yards. It was getting dark and while I didn't rush, I would like to think that I could have shot better. The speed was 2850 FPS with and SD of 9.9 as reported by Labradar. This is about 16 FPS slower than the rifle shoots the 108s so, two to three tenths more powder might tighten the group. The ELDs shoot an average of .75 MOA.

My inclination at this point is that this might be a good substitute bullet that is currently available, relatively inexpensive and looks like it would work fine for shooting steel at longer range. Will add a few tenths of powder report back with findings...

Hope you all had a good Thanksgiving.

Henryrifle

 

[r.tenorio671]

Tested with some 107 Sierra MatchKings today. After deciding to go to the range late, I loaded 20 rounds of the 107 SMKs over what is working for me with the 108 ELD-Match bullets, 29 grains of CFE 223. The temperature was in the 62 to 66 degree range today where I have done almost all of the previous testing.

I shot four 5-shot groups with group sizes of .97, 1.02, .96 and 1.01 MOA at 100 yards. It was getting dark and while I didn't rush, I would like to think that I could have shot better. The speed was 2850 FPS with and SD of 9.9 as reported by Labradar. This is about 16 FPS slower than the rifle shoots the 108s so, two to three tenths more powder might tighten the group. The ELDs shoot an average of .75 MOA.

My inclination at this point is that this might be a good substitute bullet that is currently available, relatively inexpensive and looks like it would work fine for shooting steel at longer range. Will add a few tenths of powder report back with findings...

Hope you all had a good Thanksgiving.

Henryrifle

Henry, just out of curiosity, are you loading only based on COAL or CBTO when you switch bullet brands? Asking because of the ogive type differences between the Hornady & Sierra bullets and the corresponding amounts of jump difference each impart.

 

[Henryrifle]

I always load CBTO. I will say that the SMKs are remarkably consistent. After loading them all, I checked all of the OALs and all were the exact same except one.

Henryrifle

 

[ormandj]

I always load CBTO. I will say that the SMKs are remarkably consistent. After loading them all, I checked all of the OALs and all were the exact same except one.

Henryrifle

Non-polymer tipped bullets do tend to be more consistent in this regard.

 

[Yondering]

Henry, just out of curiosity, are you loading only based on COAL or CBTO when you switch bullet brands? Asking because of the ogive type differences between the Hornady & Sierra bullets and the corresponding amounts of jump difference each impart.

Looks like Henry is squared away but that's a great point to bring up for those who are a little newer at this.

A really good example I encountered recently is the 90gr Sierra TGK and 90gr Hornady ELDx. (Another member here sent me a few samples to try, thanks again!!) One might be inclined to think since they're both 90gr bullets (and even both polymer tipped modern designs) that they'd be capable of similar velocity; this was not the case at all. The Sierra TGK has a much longer nose than the ELDx, which results in a much longer OAL when seated to the same distance off the lands (measuring CBTO). This also results in more internal case capacity, and in the case of these two bullets, keeps the base of the TGK above the neck/shoulder junction while the ELD had to be seated below the shoulder. The end result - with all other components the same, working up loads for each produced a max of ~3050 fps for the ELDx and a max of ~3150 fps for the TGK from my 24" barrel.

 

[eugevita]

I have a ballistics advantage barrel on a Larue 6.5 Grendel. Settled on a light weight carrier with a standard gas block. Runs well with and w/o a suppressor.

Awesome!

sounds like my build will be very similar to yours! What kind of accuracy are you getting? Let me know if you have any additional tips

 

[Silverjay]

All I did was remove the Larue 6.5 Grendel barrel and slide in the BA barrel. Fit was reasonably tight, but did not require heating. After firing 20-30 rounds I switched carriers. Factory 108’s were shooting just under 1 moa, 105’s are more like 1.25-1.5. 108 hand loads are 0.5-0.75 moa. My barrel shoots better than I expected for what they cost.

 

[eugevita]

Good to hear! Thank you!

Why did you choose to switch the BCG?

 

[Silverjay]

Was ejecting to the 5:00 position, light weight carrier brought it to 3:00.

 

[eugevita]

Was ejecting to the 5:00 position, light weight carrier brought it to 3:00.

Last question

What carrier did you end up using? Just curious in case same thing happens to me

 

[Silverjay]

Rubber City Armory I believe.

 

[Jefftopgun]

Oh my... where to start.

1205 posts later (yes the entire thread), the better part of my day reading and googling all the terms used in this thread, and a registration here i am. Wanting to build an 6arc, and wanting to get into reloading. You guys are an expensive influence.

First and most pressing question, I have a 7.62x39 bcg, am I grasping at straws thinking a bolt change will alleviate the need for a whole new carrier?

I resisted doing any other googling, including searching and pricing parts on this build, until I finished all 25 pages. This thread seems to have all the info I need, mag choices, barrel manufacturers, bcg options, even some pretty good load data with relevant powders (as well as what to look for in terms of overpressure).

I did have another question, when reading the difference between COAL, and CBTO. I seem to remember some people having a hard time loading to match Hornady's claimed velocity numbers initially (this was like 15 pages back), but then a comment about the loads not seeming to be on the anemic side with regards to the 52ksi number. Anyone still sitting on a box from the first 2 batches willing to chrono a few hand loading the long cartridges and comparing this to one that's been seated at the correct depths? Curious as to the difference 45-50 thousandths makes on the boom from the same charge. May not be much of any, as Henry showed speeds all within the same SD with I think 15-20 thou across his range, but that may be powder specific, and I also saw in here Hornady pretty well filled the case with whatever powder they chose, so does getting to to the point where your compressing the powder ramp up the pressure quicker? (Remember, never reloaded a day in my life, so be easy please, its my first time ).

Lastly, how does this compare to a true .243 ar10? I like fast shooting rounds, I'd like to crack 3-3200k fps, 80-90gr bullet (87vmax maybe?), out of say a 20-22 inch arc gun. I know this was a purpose built long bullet short fat case flat flying long range cartridge,just thinking out loud what other possibilities there are in getting outside of the norm 103-108 projectile. You know, all of this before I own the barrel or my first pound of powder, back to lurking.

 

[SupressYourself]

Lastly, how does this compare to a true .243 ar10? I like fast shooting rounds, I'd like to crack 3-3200k fps, 80-90gr bullet (87vmax maybe?), out of say a 20-22 inch arc gun. I know this was a purpose built long bullet short fat case flat flying long range cartridge, just thinking out loud what other possibilities there are in getting outside of the norm 103-108 projectile. You know, all of this before I own the barrel or my first pound of powder, back to lurking.

While the 6 ARC is a very efficient cartridge, it's not a 243 Win or 6 Creed. I've run the 87 vmax in 22" versions of all three. 3100-3200 fps is very doable in the 243, but that case is running (on average) 10+ more grains of powder.
I'm running 28.9 grains of H4895 in my 22" 243 LBC (which is practically identical to the 6 ARC) behind a 87 vmax and getting 2950 FPS. I have no doubt you could crack 3000 fps with Lever or CFE223 with that bullet, but at the expense of temperature stability.

IMO the 6 ARC or any of the 6mm Grendel variants are the perfect varmint round. Small enough to run in a handy AR15 platform, yet with enough power to reach out and touch something. It also seems like a great deer round, but I haven't personally used it for that yet.