The "notorious" Grendel bolt failures were not as frequent as a few posters would love for everyone to believe, and was normally the result of someone pushing pressures someone in a bolt gun would blush at. That said, you'd start seeing lug setback and/or then it would sheer a lug or two . Either way, I'm not aware of any catastrophic failures. Just keep up a proper maintenance schedule and keep an eye on your bolt as you should with any gas gun. The factory ammunition isn't going to be pushing pressures, so don't worry about it if that's all you shoot. Obviously, your mileage may vary if you use pot metal bolts.
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New 6mm Advanced Rifle Cartridge
- Thread starter Gtscotty
- Start date
The "notorious" Grendel bolt failures were not as frequent as a few posters would love for everyone to believe, and was normally the result of someone pushing pressures someone in a bolt gun would blush at. That said, you'd start seeing lug setback and/or then it would sheer a lug or two . Either way, I'm not aware of any catastrophic failures. Just keep up a proper maintenance schedule and keep an eye on your bolt as you should with any gas gun. The factory ammunition isn't going to be pushing pressures, so don't worry about it if that's all you shoot. Obviously, your mileage may vary if you use pot metal bolts.
The only 10.5" I have presently is a 5.56. A 10.5"-12" in 6mm ARC offers about the same trajectory (slightly flatter) but twice the bullet weight, with some of the current festivities in mind I'd expect a 90 grain GMX from a 6mm ARC "pistol" to do a LOT better through sheet metal and safety glass than most if not all 5.56 from an equal barrel length. Read the whole thread up to here, took me a few days
I get your point - and I'm not being snotty but that's why I mentioned the other cartridges with plenty of good bullets choices. Every cartridge has certain benefits and attributes and might work better for one application than another.
I didn't say it was a bad idea using a pistol length barrel for 6ARC, just not what I would want to do.
That was my favorite bullet in my old 6-284 as well. 700Y prairie dog is still my longest kill.
I just finished a 6 Arc barrel for my Desert Tech MDRX, absolutely my favorite by far.
You'd be surprised how well my 12.5" barrel works.
Your earlier comments about this working best in long barrels is the same thing that was said about the 6.5 Grendel for a long time as well. Funny how those actually using short barrels know differently, and those who don't prefer to guess about their choice being best.
coldboremiracle:
That is a great looking build. I have to know more about the barrel like manufacturer, twist and length. Also very interested in the details of the ammo you are using. And, GREAT SHOOTING!!!
Henryrifle
That is a great looking build. I have to know more about the barrel like manufacturer, twist and length. Also very interested in the details of the ammo you are using. And, GREAT SHOOTING!!!
Henryrifle
Thats a 20" K&P 7.5 twist, it LOVES Hornady 105 BTHP's over 28 gr of BLC 2. I need to chrono it still, but Im guessing its right around 2700. Ive taken it out to 1200 so far with pretty good results.
Really nice vid Coldbore. Loved that 1197yd rock hunting and those 100yd groups live up to its benchrest heritage. I'm v excited about my 6ARC build... come on Craddock, get that f'in barrel done!
Agree with jbailey--great video.
My barrel is 1.75" longer than yours but Quickload says 28 grs. of BLC2 under the 105 BTHP would give me 2685 FPS. If your barrel is faster than mine then you are right on with your speed estimate.
Thank you again for the info and the great vid!
Henryrifle
My barrel is 1.75" longer than yours but Quickload says 28 grs. of BLC2 under the 105 BTHP would give me 2685 FPS. If your barrel is faster than mine then you are right on with your speed estimate.
Thank you again for the info and the great vid!
Henryrifle
I'm not surprised at all but it's not what I would grab out of the safe for 500Y+ shooting.
I'm not saying you can't hit stuff with short barrels at whatever distances, heck people are slinging 22rf at 1000Y. So "best choice" for what??? I've shot my 15" AR in 223 at 1122Y with 70's and hit steel. I'm sure I could do the same thing with a 12.5" barrel but why???
Because - velocity, BC, and energy, I'll take a longer barrel and sacrifice handyness, that's how I am.
""Funny how those actually using short barrels know differently"
Take your 12.5" to a long range match and see how that goes "would you prefer to guess" about the outcome??
I've won a long range steel match against all the rest of the bolt rifles with my (26" 6mmART40 AR) and usually finished high on the roster in the rest of the matches I shot it in. Also got 2nd place at the Score High challenge back when I had it, against 100-ish bolt rifle shooters. Why? because it didn't have it's balls cut off by using a short barrel.
All I'm saying is be realistic about barrel length, cartridges in those lengths, and what they excel at and what they don't.
I wouldn't personally cut the balls off a 6mmARC by using a 12" barrel, that's me.
Yondering, here's a quote from you back in post #36
""As much as I like the 6mm Grendel family of cartridges, IMO for a 12.5" I would choose the larger 6.5mm bore.""
Actually I'd rather use a 6.5G too with a barrel that short for the heavier bullets but that's not in the future for me.
The question for some of us is "what ctg do you use in a 10.5"-12.5" barrel", the arc looks pretty darn good. Nobody proposed that it was a do all proposition. Chopping off 6" of barrel we only lose about 250 fps, 10% pretty much, hardly "cutting the balls off" ;-).
Bill
Inspired by @coldboremiracle, I loaded up 50 of my most consistent load, 28.3 grains of CFE223 under the 108 ELD-M and headed to the 1000 yard range. At 100 yards this consistently groups in the .7 to .8 MOA range at 2590 FPS. I am not at all happy with this group size but I know it is consistent and that is what I needed for today. I also decided to get back to the basics using only a Harris bipod, rear squeeze bag and prone shooting mat. Starting at 200 yards and putting two shots on each target, the hits looked to be about an inch apart at 200.
Using the Applied Ballistics app, I moved out cleanly to 300, 400 and 600 yards without any misses. the rounds were hitting a little high by 600 yards so, at 700, I stopped and ran the ballistic calibration within the app. There was also a 5" gong at 700 that was fun to put successive hits on in almost "rapid fire" succession.
The 800, 900 and 1000 yard gongs are all 20" and provided little challenge for the rifle/load combo. There was a 1/2 MOA or 5" square at 1000 yards. That did prove to be very challenging. I was running low an ammo and didn't want to end such a fun day on a miss so I loaded a 10-round mag for the 5" gong. Only 3 out of 10 for hits but, you could easily see the splashes around the target and make a good correction for a reasonably fast follow up shot.
The remaining rounds I shot at 700 to 1000 yards without any misses.
Takeaways from today are that this is easily a 1000+ yard capable cartridge. There were no failures of any kind with the rifle today; it is relatively light weight, very manageable on a bipod and produces very little recoil allowing the shooter to spot hits and misses.
Will continue with more disciplined load development but happy with the knowledge that I can have fun on the long range while engaged in the minutia of load development.
Very cool little cartridge!
Henryrifle
Using the Applied Ballistics app, I moved out cleanly to 300, 400 and 600 yards without any misses. the rounds were hitting a little high by 600 yards so, at 700, I stopped and ran the ballistic calibration within the app. There was also a 5" gong at 700 that was fun to put successive hits on in almost "rapid fire" succession.
The 800, 900 and 1000 yard gongs are all 20" and provided little challenge for the rifle/load combo. There was a 1/2 MOA or 5" square at 1000 yards. That did prove to be very challenging. I was running low an ammo and didn't want to end such a fun day on a miss so I loaded a 10-round mag for the 5" gong. Only 3 out of 10 for hits but, you could easily see the splashes around the target and make a good correction for a reasonably fast follow up shot.
The remaining rounds I shot at 700 to 1000 yards without any misses.
Takeaways from today are that this is easily a 1000+ yard capable cartridge. There were no failures of any kind with the rifle today; it is relatively light weight, very manageable on a bipod and produces very little recoil allowing the shooter to spot hits and misses.
Will continue with more disciplined load development but happy with the knowledge that I can have fun on the long range while engaged in the minutia of load development.
Very cool little cartridge!
Henryrifle
Good stuff you got going there. Any idea on the temp stability of that powder? Been thinking of trying it in a couple cartridges.
Why? Because this cartridge in a 12.5" barrel is significantly easier to hit with at even 500-600 yds than a 16" 5.56 if there's any wind, and much more so farther out. I'm speaking from experience, comparing the 105gr BTHP to the 75gr BTHP in my 16" 223 Wylde, both are my own accuracy loads. The 12.5" 105gr starts off a little slower (2500 fps in my barrel, vs ~2650 for the 5.56) but the long distance trajectory is significantly better with less wind drift. That's why. Are you still not surprised?
Sure, the same cartridge is more capable in a longer barrel, but even in a short barrel it's more capable than you seem to realize.
I still believe the 6.5 is probably the better choice for hunting. But for distance there is no question the 6mm is about as good as it gets in the AR platform. I have 12.5", 19", and 24" flavors at this point because it's useful at all of those lengths.
Yup. I can confirm that between 24" and 12.5" (both barrels from the same maker), my 105gr / Lever load loses 340 fps, and about 230 fps compared to the 19" barrel.
I dont think BLC2 is very stable, I actually blew up an AR many years ago using BLC under 75 Amax's. The load was developed in the fall, and I foolishly pushed it to the edge, then months later on a hot July afternoon, my AR spilled its guts all over the Wyoming prairie.
For that reason alone, I kept the load in my ARC what seems to be a safe margin away from max pressure. Load was developed and tested at the peak of July heat, with no pressure signs at all.
Okay being in a fine mood this morning I'll compromise, well then you cut one ball off.
You basically turned your nice little long range 6mmARC into a 6.5G one baller which always was anemic.
You basically turned your nice little long range 6mmARC into a 6.5G one baller which always was anemic.
BLC2 is not temp stable and it quickly builds to overpressure. But it is a fairly predictable temp curve, so if you do the work and have a ballistic app that models temp based MV, it is very usable in a 6PPC based cartridge (6ARC, 6.5G etc). It does produce some of the best MVs as well. But don't drive it on the ragged edge of pressure as a hotter than normal day might not be fun.
I'm also interested in testing 2000MR in this cartridge. I think it could offer some good MVs and its very temp predictable.
What's the general thought around barrel life? 2k rounds? Assuming inherently less barrel life due to semi-auto increasing rate of fire, producing hotter and longer rounds of fire.
The faster 6mm cartridges burn up barrels in the neighborhood of 800-1200 rounds. If you get more, you've done well.
The faster 6mm cartridges burn up barrels in the neighborhood of 800-1200 rounds. If you get more, you've done well.
Bore area to powder charge is only slightly worse than .223. Plus running cooler burning spherical powders at 52ksi it's probably going to be north of 3000 rounds unless you mag dump routinely. I know of one AR-15 barrel that has 2k+ and is still running strong. My bolt gun barrel just broke 1000 in the last couple weeks and looks like how a 6 creed that has 150-250 rounds on it looks. Like 1/4" of 'heat affected' throat (not even fire cracked yet), and brand new shiny everything else.
I shoot the .224 Valkyrie AR with. 2000mr load of 26.2gr with the heavy 95gr SMK. I developed that load in cooler weather and had some flyers at a match that crept up to around 75*. Looking to try another powder for that round because of the instability. But like you say, maybe a hot weather load and a cooler weather load are worth the effort. The speeds were decent bringing accuracy out past 1200y, when temps were agreeable. I’m going to try the 2000mr in this cartridge as well, whenever the barrel gets here from Craddock. I’ll try to post results in a couple months.
Really hope desert tech offers the MDRX in 6mm ARC that would alleviate most of the issue with a small form factor 6mm ARC. @coldboremiracle How long is that MDRX without the can?
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As to the idea that the 10" 6mm ARC is some fresh atrocity spawned from hell .
Not really a whole lot different, maybe 3 grains water more case capacity and a rifling twist setup for heavier bullets. The original Contender was fine with SAAMI 223 loads, the one pictured is a G2.
Bill
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Not really a whole lot different, maybe 3 grains water more case capacity and a rifling twist setup for heavier bullets. The original Contender was fine with SAAMI 223 loads, the one pictured is a G2.
Bill
About 33-34 inches? Very mobile. I can literally drive around with it riding in the middle seat low, pull it up into the shooting position from the driver's seat if needed. 20 round mags, sub half MOA accuracy, anything inside 1000 is a pretty easy hit, its a truck gun on steroids.
Precisely why i hope they start offering it. Seems perfect for a do it all.
There is supposed to be an abbreviated (easy) way to challenge patents that were “improvidently granted”. Your “prior art”, at least in theory, should be a slam dunk.
Patent law has moved to "First to File" so prior art is no longer the exact point of invention to the courts. I am not in agreement with this stance ...
You also have to defend a patent for it to remain valid. That is what sucks about the china direct outfits that copy products, the maker patent holder has to take action against them or the patent becomes invalid if I understood it right. He is not making any money from his patent so probably will not spend any to defend it. So if say a half dozen people popped up making the item and offering it for sale he is probably not going to hire a lawyer and go after all 6 ;-).
Bill
Bill
This is correct, at least for the 6.5G. Velocity/inch gains of about 25 FPS above 12" or so. It varies a bit, for sure, but in a couple of barrels I cut down, one 20", one 18", I only lost about 25 FPS per inch. I run them @ 16". My friend/regular hunting buddy uses one cut down to 12.5 and gets about 2,300 w Hdy Black 123gr, the same ammo my 20" gave me 2,550 with. I just got a reamer and barrel blanks, I'm going to see what the 6mm ARC does, but the 6.5G doesn't lose much when cut down in my own and my friend's experience.
--HC
I have a 12.5" grendel and was on the top end of my load with ARComp to get 2300fps. Which why i'm now thinking a bullpup alleviates all that issue while keeping the same form factor. I'd be interested to see what a 12.5" 6mm ARC can do.
Hornady was kind enough to do the testing .
https://www.hornady.com/assets/site/hornady/files/load-data/6mm-ARC-gas-108-110gr-data.pdf
.https://www.hornady.com/assets/site/hornady/files/load-data/6mm-ARC-gas-108-110gr-data.pdf
Bullpups are one of those great ideas that fall apart (for me) when they meet reality. I own quite a number of them, and this is obviously different for everyone, but ergonomically you are trading off a lot to get that short OAL. I love the weight balance, love the OAL vs. barrel length, but they are awful to deal with stoppages/mag changes/etc, even with a lot of practice. Most of the triggers are mediocre at best, and awful at worst - even the aftermarket triggers. Even though I've got a bunch, they rarely go out anymore, I'd rather lose some velocity with the shorter barrel and make up for it with ergo/trigger/etc.
With the MDR/MDRX, make sure to go look up the reviews regarding reliability; it's no AUG.
Can you load a magazine on a closed bolt yet? Poly cracked? Pins broken? I could go on and on. I was one of the first reservation holders of a few MDRs, and boy oh boy, that was a lot of fun. I've heard they addressed some of it with the MDRX, but the MDRs had some serious issues. I can't even remember how many 'recalls' or 'fixes' were put out, and they still never worked right. I didn't mean to trash it, just point our ergo issues as I haven't personally owned a MDRX, but the MDRs were pieces of work, and not good pieces.
If I were going bullpup today, in that style, it'd be an AUG if I cared about reliability any day of the week.
That said, I've moved on to other platforms, the ergos just don't work for me. I'm sure for others they are fine. I have longer arms so it's too awkward to manipulate re: magazine changes and clearing malfunctions just plain sucked, especially with forward eject models like the F2000 and RFBs.
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Proof Research Stainless Steel 6MM ARC Barrel - 16\\\
Proof Research Stainless Steel 6MM ARC Barrel - 16\
www.rainierarms.com
Hornady was kind enough to do the testing
https://www.hornady.com/assets/site/hornady/files/load-data/6mm-ARC-gas-108-110gr-data.pdf
Sure, except something is really wonky with their velocity numbers. Their charge weights match pretty closely to what I'm using, but their velocity numbers are way low for the same barrel lengths. Their numbers don't really line up with their factory ammo specs either; sure maybe they use a special canister powder in the factory stuff but a lot of us wildcatters have been getting the same speeds for years with powders like Lever and CFE223.
My 21" Odin works barrel gets 2740 with their factory 108 eld ammo and it hasn’t broken in yet. Their numbers seem low, which is a good thing IMO.
I have that was the gen I and apparently has been rectified. I do understand where you’re coming from they’re different. And the triggers usually suck but if the trigger is half as close as the SRS I’ll chance it. The SRS trigger is phenomenal.
For what i want out of it though which is hunting/truck gun and target plinking it fits the bill perfectly even if it might require a little work on my end. My SHTF rifle is a 11.5” 5.56 if the need ever arises
I had an SRS A1 Covert, too. Sold it for ergo reasons, no major issues. The trigger was great for a bullpup but it wasn’t a TriggerTech Diamond.
They definitely have their place and if the ergos work for you awesome!With one of the powders on the list, maybe. Look at the chart closer and compare the numbers, it's pretty clear the extrapolated (at best) all the other powders from whichever one they tested. I'm betting their test was only one sample as well, with an apparently very slow barrel. The velocity numbers in that chart seem to be at least 200-250 fps* slow compared to a good barrel.
Part of my profession is analyzing data like this. Just because it's published data from a reputable company (and I do like Hornady as a company) doesn't mean it's good data. When you see red flags in the data like on that chart, it's wise to do more research before accepting it.
*Edit: I have to retract my statement about velocity - I was looking at the wrong line for Lever numbers like a moron. I still think they might be a little on the slow side for that charge weight, but within 50-100 fps, not 200-250. Sorry about that.
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