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I've been thinking about stepping up from my Grendel to a new round. I've been looking at the 6mm ARC. Is that round based off the Grendel/7.62x39 case? If so, does it use the same bolt? Is the bolt face depth compatible with Type I or II Grendel bolt? What about bullet seating depth? I understand it's kinda shallow.  Will the case have to be crimped because of that? I would like to share common parts with my 7.62 and Grendel Type I if possible which may mean a custom barrel. Any other long range round that fits on the AR15 frame? 

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I cannot answer this, but I will sure like to read and see what you come up with. 

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There's the .224 Valkyrie, but from what I'm seeing the 6mm ARC outperforms it..

 

7 hours ago, xonlyj said:

I've been thinking about stepping up from my Grendel to a new round. I've been looking at the 6mm ARC. Is that round based off the Grendel/7.62x39 case? If so, does it use the same bolt? Is the bolt face depth compatible with Type I or II Grendel bolt? What about bullet seating depth? I understand it's kinda shallow.  Will the case have to be crimped because of that? I would like to share common parts with my 7.62 and Grendel Type I if possible which may mean a custom barrel. Any other long range round that fits on the AR15 frame? 

 

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It is based on the 7.62/Grendel. Factory bolts are TYPE II 0.135.  What's funny is that is the same as a Grendel AUTO. My GRENDEL RUGER BOLT is a 0.125.  Now why do you think Ruger did that? HMMMM? I can tell you why but then I'd just be called stupid and be canceled in many places outside of here..LOL

 

It has a bumped shoulder compared to a Grendel and long neck and is pointing at the heavy bullets. It's capacity is not grate and is basically equivalent to a Valkyrie that is barely bigger than a 223. 

 

You will have to convince someone to run the reamer in another 0.010 deeper to use your bolt so you are talking custom right there.  Unless you have access to someone that will do that as a courtesy you are out some more $$$'s as it will be custom and  if so make dang sure the barrel is engraved that way. otherwise when some one sticks a TYPE II bolt in it you MAY have some case separation but then that's a world I play in carefully.

 

Unless you are dead set on shooting heavy bullets  I wouldn't bother. The 6X45 will hang with it up to 87 grains. It is a step down from the 243 LBC by quite a bit and really the LBC is no harder to load than the ARC. You could actually use ARC dies to make and load it with far superior brass and still use your TYPE I bolt.   The LBC will handle anything that you want at long range in 6 MM.  The 22 LBC will also do the same.  Of course these are not OTC chamberings but based on my experience shooting FACTORY ammo in a FACTORY chambering it will be a crap shoot in many instances. I would hate to be wedded to factory ammo on something that I want to use in the next ZIP code.

 

The case would not require crimping as in fact none of these do but if you want that working for you it's just a quarter turn on the die.  As this is a 2.260 COL SAAMI set up be aware that virtually ZERO cannuelures will be in the right place for true old style crimping.

 

Just my thoughts but I can say I do have a smattering of knowledge on these 6.5 variations.

 

Greg

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Let's see if I got this right. The 243 LBC uses a Type I bolt and uses a Grendel mag. I started on the ARC rabbit hole because of an article I saw. Military acceptance and a few OTC mfgs out there interested me. Figured that the reamer would have to go that extra .010" which would make it a potential risk of mixing bolts. Good point about remarking the barrel. Regarding the cannuelures, I already load my 7.62x39 BT pills before the band. This will get me thinking. Gotta look up the ballistics of the rounds mentioned. 

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You have the bolt figured out. As to the military deal I would not buy in real heavily on that. The 6.8 SPC was presented with the same fanfare and it still whimpers in the corner of the US military.

 

The Grendel sized case is a bit finicky in full auto when you wrap it up in a small package per report.

 

Small groups use all sorts of non-standard stuff in the theatres of war. Small groups are easy to supply. A major overhaul is probably not only cost prohibitive but logistically a nightmare to manage.

 

As I said if you don't shoot heavy bullets the 6X45 is the way to go. Out to 500 it does an admirable job on target. I've shot the 6X45 , the 6X6.8 and the LBC extensively at 500.  Each step up was a boost in speed and TOF does matter in my usage. 

 

OTC ammo is cool but I've never seen ARC ammo on the shelf and the way things look I don't expect any in the near future. The good thing is you can make it out of Grendel brass but personally I want the full capacity of the case just like I like 10 MM over the 40 S&W.

 

This last go around I used ARC data as a starting point for my new 243 LBC and moved up. It worked well and ran over the top of the new guy.  I may well build one but you know me. I just gots to know.

 

I shoot the 22 Valkyrie, the 22 Nosler, the 22X6.8 and the 22-NXS. Each is a step up from the last. Each has its use and I've found the 6MM camp the same way. I even have a couple other 6 MM's tucked away in the mix that aren't worth the effort but by golly I'll have my ducks in a row when it comes to a ballistic throw down.

 

My assessment of many shooters is the Walter Kitty is strong in them. You don't see them laying on their belly or even shooting off a bench. They are busy reading about others exploits and via osmosis they become Carlos Hathcock or Gary Anderson. One thing for sure the gun manufacturers are not unlike the guys at Rapala. Make it pretty and flashy and fishermen along with shooters will empty the shelves.

 

Greg

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OK, I've done a little research and find I can get dies for the 6mmARC and 6x45 but not the 243 LBC. Did I understand correctly that the ARC die can be used to resize Grendel brass for the LBC? Without knowing bullet data, it's seems difficult to compare ballistics. On average which round has the best speed and/or energy generally? What about bullet weight? Doesn't a heavier bullet drift less? Yeah, I get the Walter Mitty reference. I'm half that and half into the discipline and sub MOA. I'm no hunter and too old to play sniper. I just enjoy trying to improve and reach out a little farther. Mostly shoot bench but am not adverse to prone. I stay away from the big bores as I have had my shoulder replaced and don't want to rattle it loose.

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The DoD has accepted the ARC for something...they won't tell us what fer yet. 

 

A good number of manufacturers will be supporting the cartridge, including Ruger,  so you should have what you need before too long.

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5 hours ago, xonlyj said:

OK, I've done a little research and find I can get dies for the 6mmARC and 6x45 but not the 243 LBC. Did I understand correctly that the ARC die can be used to resize Grendel brass for the LBC? Without knowing bullet data, it's seems difficult to compare ballistics. On average which round has the best speed and/or energy generally? What about bullet weight? Doesn't a heavier bullet drift less? Yeah, I get the Walter Mitty reference. I'm half that and half into the discipline and sub MOA. I'm no hunter and too old to play sniper. I just enjoy trying to improve and reach out a little farther. Mostly shoot bench but am not adverse to prone. I stay away from the big bores as I have had my shoulder replaced and don't want to rattle it loose.

 

You can form LBC with the 6 ARC by adjusting the height of the die above the shell holder.  Ideally we use Redding bushing dies or a custom die made by CH4D. They often have those on the shelf BTW  I furnished theme the prints on it and the 6X6.8. I feel the bushings are superior as you can adjust for neck tension and you cannot do that easily with the regular die types.

 

The LBC will out do the ARC in speed/energy pretty much across the board thanks to raw case capacity even if you have to stuff the bullet down in the case. The LBC chamber will let you load way out past 2.260 and you can use that if you want to go heavy but realistically unless it's only paper anything over a 95 is superfluous in either. 

 

Heavy bullets in and of themselves do not shot flatter. It is bullet SHAPE that makes the huge difference.  A solid copper bullet of the SAME profile as a cup and core pill will end up with the same drift as the heavier one as a function of ballistic coefficient though being lighter you could push it faster than the OG type and do better on drop/drift..  Penetration on target will be different in the same profile but different weight types also. 

 

 

The 6X45 is a FINE round but gives up 150-200 FPS in velocity to the LBC and maybe 100 to the ARC although you can load the 6X45 to 62,000 and come very close to the ARC. The go to bullet on a 6X45 is an 87.  Western/Accurate Powdres are your friend on 6X45 load data.  Hornady has ARC data and the 243 LBC uses the ARC stuff as starter loads for the less adventurous types.    Be aware that in an AR the ARC/LBC should not be run above about 55,000 but preferably around 53,000 for good case life. If you run it in a bolt gun up to the projected 62,000. per Hornady step back and watch the numbers move up but brass life is going to go down.

 

Greg

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4 hours ago, Retcop said:

The DoD has accepted the ARC for something...they won't tell us what fer yet. 

 

A good number of manufacturers will be supporting the cartridge, including Ruger,  so you should have what you need before too long.

 

Yes just like the claim the 6.8 SPC was adopted by the military also.  Sure they bought some but "adopted" would be a long stretch there IMHO.

 

Greg

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17 hours ago, GLShooter said:

 

Yes just like the claim the 6.8 SPC was adopted by the military also.  Sure they bought some but "adopted" would be a long stretch there IMHO.

 

Greg

 

That's why I wrote "accepted the ARC for something"  instead of adopted. 

My guess is that they want to play with it and see what they think. IIRC, the Military ballistics gurus where in touch with Hornady while they were making and tuning the ARC. I'd like to know what projectiles, velocities, and pressures the Military

has in mind off the bat, if their intent is to re-barrel existing AR's. In the latest MRA article, they did a good job of mixing in specs from a 16 inch barrel with a 23.5 inch barrel.  I'd also like to know the weight of the ARC round with the 103 and 108 grain projectiles, as a bif selling point of the 5.56 was that the troops could carry more ammo. That does not do a lot of good when your enemy has figured out to stay past the distance of reliable 5.56 hits, especially in the windy mountains of AFG. 

 

For civilian sales, 6mm (.243) makes perfect sense, since most States frown upon using 22. caliber bullets on the country's most populate big game animal, the Whitetail. IIRC, the recoil energy is about 1/3 of the .308 Winchester, which should make many people happy. For the Military, I still like them to bump things up a bit.  

 

The good news is the USA is still looking for a better true intermediate cartridge, maybe one that will be used with the next gen of computerized sights for aimed fire. Until then, the doctrine will remain massed fire and the expectation that close air to ground support will be available.  Since I did not serve, maybe these stories I read of our troops getting outdistanced with their M4's, is something I take too seriously. Maybe those who have served or are serving with the M4 in our 20 year war against the caliphate can tell me if our troops getting outdistanced is not a great concern, even when the birds cant fly.  

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20 hours ago, GLShooter said:

 

Yes just like the claim the 6.8 SPC was adopted by the military also.  Sure they bought some but "adopted" would be a long stretch there IMHO.

 

Greg

 

 

The Asymmetric Warfare Group does lots of real world testing of such cartridges as well as other gear & such along with tactics and a bunch of other stuff, but big Army announced it's shutting down AWG next year......

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I read the 6mmARC article in American Rifleman too.  Its an interesting cartridge but not being a reloader, I have to stick to factory ammo for all my rifles.  The article outlines some good ballistics with heavier bullets not seen with other similar cartridges.  It may be slightly better than a Grendel but I see no reason to go head over heels for the new kid on the block.  As we have seen in recent history, there are dedicated people working on the next round that is "better" 

 

Reloading interests me, maybe after I retire and have much more time to piddle.  Maybe by that time the whole firearms market will settle down.  I will hafta put some thought into it ahaed of time because I retire in 2024 so here we go again with election based crazed buying.  All of that too depends on whether or not Crazy Joe and company do not destroy the firearms industry by then. 

 

One thing for sure is as prices hopefully start to settle back to the earth I am not going to hesitate to lay in more ammo and seriously start looking to buying a reloading set up for my guerrilla camp house in the woods.  Gonna raise some chickens and a piggie or two, grow some veggies, shoot an occasional squirrel and work a reloading press.

Edited by hlhneast

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