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6mm ARC Thread
- Thread starter Mountain
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I have about 600 Nosler 105 RDF's not really using them I can send you some to load test if you want.Thought about a quick trip to the range at lunchtime but no reason to check group size when the wind is gusting to ~40 mph.![[laugh]](/xen/styles/default/xenforo/smilies.vb/012.gif "Laugh [laugh]")
Ran some loads at quick lunch outing today- both with Berger Match BT 105's set at 2.26 COAL. One with 27.0 grains of Varget and the other with 28.0 grains of 2520. Neither were terrible but the Varget load needs more work. Varget groups averaged over 1 MOA with best group .95 MOA. The 2520 groups excepting one group were sub-MOA with an average of .82 MOA. Best 2520 group was .65 MOA which is as good as I expect at this early stage of load development. Nice and sunny at the range but a bit breezy with a 10-15 mph crosswind.
Both brass and rifle ran much cleaner than with the factory Hornady ammo. Brass was less beat and primers less flat. Looks like I can run the loads a little hotter if I want, not that I recommend anyone do that.
If I can keep this thing below 1 MOA with a ~0.8 MOA average, I'll be happy with it. Seems like with a little more work ~0.6 MOA average is attainable.
Both brass and rifle ran much cleaner than with the factory Hornady ammo. Brass was less beat and primers less flat. Looks like I can run the loads a little hotter if I want, not that I recommend anyone do that.
If I can keep this thing below 1 MOA with a ~0.8 MOA average, I'll be happy with it. Seems like with a little more work ~0.6 MOA average is attainable.
Found some Hornady Black 6mm ARC 105's for a reasonable price and a couple hundred are on the way. Doesn't have Hornady's plastic tips, which I don't care for even if Hornady were to package them well enough to prevent the tips from getting bent. If it shoots so-so like the Match, I'll at least have more brass.
Granted I was farting around with the new adjustable gas block, but relative to group size the Hornady Black 105's were similar, maybe slightly better than the ELD's. Best 3-shot group was 0.83 MOA but they were mostly a hair under MOA. Best 5-shot group was 1.11 MOA but most were ~1.5 to 1.75 MOA. Messing with the gas block probably didn't help, and the groups were the largest when I had the gas block closed down too much. In the end I adjusted the gas block almost all the way open for reliable function.
'Autopsy' of the Hornady Black 105:
OAL - 2.202", though a couple were ~2.189"
Bullet - 1.228", 105 grains
Powder - 30.44 grains, looks like same ball / spherical as the ELD's. Probably Leverevolution or their bulk equivalent.
Jump to lands - ~0.072", but some 0.085
Assuming the powder is Leverevolution, that charge exceeds what they list as max for gas guns (29.5 grains), and IIRC the 'Black' was designed for gas guns. Their Leverevolution max charge for bolt guns is 30.8 grains, so the 30.4 in this ammo is very close to that. Primers are pretty damn flat. They are not cratered, but that could be a factor of Wilson Combat having a nice tight tolerance for the firing pin, much like JP does for their high pressure bolts. Glad I took my own advice to go with a top shelf bolt, especially for this caliber which has a thinner outer rim.
Here's a pic of the 'Black' 105 flattened primer (bottom) vs. a primer from my 2520 & Berger 105 loads:
Steve Hornady should run for office. He's got the "Do as I say, not as I do" thing going for him.
'Autopsy' of the Hornady Black 105:
OAL - 2.202", though a couple were ~2.189"
Bullet - 1.228", 105 grains
Powder - 30.44 grains, looks like same ball / spherical as the ELD's. Probably Leverevolution or their bulk equivalent.
Jump to lands - ~0.072", but some 0.085
Assuming the powder is Leverevolution, that charge exceeds what they list as max for gas guns (29.5 grains), and IIRC the 'Black' was designed for gas guns. Their Leverevolution max charge for bolt guns is 30.8 grains, so the 30.4 in this ammo is very close to that. Primers are pretty damn flat. They are not cratered, but that could be a factor of Wilson Combat having a nice tight tolerance for the firing pin, much like JP does for their high pressure bolts. Glad I took my own advice to go with a top shelf bolt, especially for this caliber which has a thinner outer rim.
Here's a pic of the 'Black' 105 flattened primer (bottom) vs. a primer from my 2520 & Berger 105 loads:
Steve Hornady should run for office. He's got the "Do as I say, not as I do" thing going for him.
i would assume varget... but it should not be too different. 30-31gr is what most do anyway.
yes, flattens primers and eventually expands primer pocket in 5-7 firings.
pretty much a rule of thumb to put varget behind 6mm 105gr bullets, tho.
and just to tease you, mercilessly, with some luck - this is 300yds.
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Continued with load development this morning- up to 29.0 grains of 2520 and 28.0 for Varget.
I would still get some flyers from Varget. Not sure if randomly me or if it's the powder. Charts show Varget getting higher pressures at lower velocities and a lower velocity at max load. One group of 4 was 0.55 MOA, but the first of 5 made that group ~1.5 MOA. Some of the groups were just under 1 MOA. The recoil impulses were sharper for Varget and the ejected brass wasn't landing in the same spot. However, no signs of overpressure. I'm a big fan of Varget for most anything from .308 to .30-06 including 6.5 CM and 7.5 Swiss. However, I think I'm done playing with Varget in this particular 6mm ARC.
No flyers from the 2520. Groups were ~.6-ish to .8 MOA, which meets my goal for this AR. Recoil impulse was much smoother than the Varget and the brass was all dumping in the same spot. Groups tightened up as I reached 29.0 grains. Probably could have shot a little better. Tried to work around the wind as best I could but in the middle of my range time my bride and kid kept calling because my kid was in a minor parking lot fender bender. No signs of overpressure with the spent cases.
The usual disclaimer to not jump in and copy my loads without working your way up. At 29.0 I am slightly over what Hornady recommends for gas guns but exactly at max per Hodgdon load data. Hodgdon 2520 at 29.0 grains shows 51,000 psi which is under the recommended 52,000 psi for this caliber in an AR. I trust Hodgdon's info way more than Hornady's. Fired primers at 29.0 grains looked no different than my above pic vs. the flattened primers via Hornady Black factory ammo.
I might kick up the load another 0.1 or two to see what happens. I also might try some Lapua Scenar L's and Nosler RDF's. The RDF's are generally cheaper and easier to find, plus they have been ~.6 to .7 MOA in my 6.5 CM AR.
Still a bit surprised how hot Hornady is loading its factory ammo. No primers popped out of my reloads, but a couple primer pockets from the 'Black' ammo were not as tight as the others. Possibly normal variance in the brass but that Hornady ammo for sure is beating the crap out of the brass. Cases take much more effort to size than do the ones I have reloaded.
Anyway I'm a lot less frustrated now that I have a series of groups that are all ~.8 MOA or less.
I would still get some flyers from Varget. Not sure if randomly me or if it's the powder. Charts show Varget getting higher pressures at lower velocities and a lower velocity at max load. One group of 4 was 0.55 MOA, but the first of 5 made that group ~1.5 MOA. Some of the groups were just under 1 MOA. The recoil impulses were sharper for Varget and the ejected brass wasn't landing in the same spot. However, no signs of overpressure. I'm a big fan of Varget for most anything from .308 to .30-06 including 6.5 CM and 7.5 Swiss. However, I think I'm done playing with Varget in this particular 6mm ARC.
No flyers from the 2520. Groups were ~.6-ish to .8 MOA, which meets my goal for this AR. Recoil impulse was much smoother than the Varget and the brass was all dumping in the same spot. Groups tightened up as I reached 29.0 grains. Probably could have shot a little better. Tried to work around the wind as best I could but in the middle of my range time my bride and kid kept calling because my kid was in a minor parking lot fender bender.
No signs of overpressure with the spent cases.The usual disclaimer to not jump in and copy my loads without working your way up. At 29.0 I am slightly over what Hornady recommends for gas guns but exactly at max per Hodgdon load data. Hodgdon 2520 at 29.0 grains shows 51,000 psi which is under the recommended 52,000 psi for this caliber in an AR. I trust Hodgdon's info way more than Hornady's. Fired primers at 29.0 grains looked no different than my above pic vs. the flattened primers via Hornady Black factory ammo.
I might kick up the load another 0.1 or two to see what happens. I also might try some Lapua Scenar L's and Nosler RDF's. The RDF's are generally cheaper and easier to find, plus they have been ~.6 to .7 MOA in my 6.5 CM AR.
Still a bit surprised how hot Hornady is loading its factory ammo. No primers popped out of my reloads, but a couple primer pockets from the 'Black' ammo were not as tight as the others. Possibly normal variance in the brass but that Hornady ammo for sure is beating the crap out of the brass. Cases take much more effort to size than do the ones I have reloaded.
Anyway I'm a lot less frustrated now that I have a series of groups that are all ~.8 MOA or less.
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Shot some more developmental loads this early evening before a club meeting. Left the OAL alone and tried bracketing the 29.0 grains of 2520 that worked so well for me with loads +.2 grains and -.2 grains. 5 shot groups averaged .595 MOA, so looks like I'm in a good sweet spot. Worst was .666 MOA and best was .553 MOA. Some of the groups had 4-shot bugholes. First 3 shots of one group were ~.25 MOA. All of these with Berger 105 BT target. I'll try the Berger 108's and some Nosler 105 VLD's as well as some Berger VLD's. The Berger Hybrids are unobtanium right now or I would try those.
The 29.0 and 29.2 grain groups had nearly identical POI's. The 28.8 grain groups were slightly left and a tad higher. Barrel dynamics / harmonics? Regardless, with an average less than .6 MOA and a max less than .7 MOA I'm going to call it time to do this:
Of course I can't seem to get to the range without forgetting something and this time it was my chronometer. I have plenty of leftover loads to get the data next time I go. Maybe I'm close to 2700 fps? VLD's should go 1200 yards before going transsonic.
Oh, I shot some more Hornady Black 105 (otherwise known as making more brass). Groups about 1.4 MOA.
The 29.0 and 29.2 grain groups had nearly identical POI's. The 28.8 grain groups were slightly left and a tad higher. Barrel dynamics / harmonics? Regardless, with an average less than .6 MOA and a max less than .7 MOA I'm going to call it time to do this:
Of course I can't seem to get to the range without forgetting something and this time it was my chronometer. I have plenty of leftover loads to get the data next time I go. Maybe I'm close to 2700 fps? VLD's should go 1200 yards before going transsonic.
Oh, I shot some more Hornady Black 105 (otherwise known as making more brass). Groups about 1.4 MOA.
Thanks, a little bit windy too. Not bad but not ideal for shooting groups. 10 mph crosswind will push a Berger 105 about .6" at 100 yards. Maybe I should leave this upper alone and once the Bartlein barrel is ready just make another upper.
Wish I would have had the chronometer. I think the loads will exhibit low variance in fps. We'll see.
Found a very good article regarding 6mm ARC. This guy developed loads for both an AR and a chassis bolt gun.
https://www.handloadermagazine.com/6mm-arc
Patrick Meitlin, April/May issue of Handloader Magazine.
In his AR, the Hornady Match factory ammo averaged a little better than I saw but the Hornady Black was much worse for him: "Hornady Black 105 BTHP factory ammunition 2.35 inches and Hornady Match 108 ELD Match 1.05 inches." I was getting 1.5" to 1.75" 100 yard groups with the Hornady Black. Not great for me, and 2.35" is pretty bad.
He considers anything less than an inch group size to be exceptional for an AR. His various AR loads achieved from .91" down to .59" 100 yard groups. In comparison, from my loads I'm getting slightly better groups now but essentially in the same ballpark.
In his MPA bolt gun, he shot some pretty amazing groups:
"Berger’s 109-gain Long Range Hybrid Target bullet produced the tightest groups of the bolt-rifle test – .26- and .13-inch groups using 25.5 and 26.5 grains of IMR-8280 XBR"
Thus far, this is the best article I've read regarding loading this caliber. Well worth the read.
https://www.handloadermagazine.com/6mm-arc
Patrick Meitlin, April/May issue of Handloader Magazine.
In his AR, the Hornady Match factory ammo averaged a little better than I saw but the Hornady Black was much worse for him: "Hornady Black 105 BTHP factory ammunition 2.35 inches and Hornady Match 108 ELD Match 1.05 inches." I was getting 1.5" to 1.75" 100 yard groups with the Hornady Black. Not great for me, and 2.35" is pretty bad.
He considers anything less than an inch group size to be exceptional for an AR. His various AR loads achieved from .91" down to .59" 100 yard groups. In comparison, from my loads I'm getting slightly better groups now but essentially in the same ballpark.
In his MPA bolt gun, he shot some pretty amazing groups:
"Berger’s 109-gain Long Range Hybrid Target bullet produced the tightest groups of the bolt-rifle test – .26- and .13-inch groups using 25.5 and 26.5 grains of IMR-8280 XBR"
Thus far, this is the best article I've read regarding loading this caliber. Well worth the read.
look better for my post #68 for amazing.Found a very good article regarding 6mm ARC. This guy developed loads for both an AR and a chassis bolt gun.
https://www.handloadermagazine.com/6mm-arc
Patrick Meitlin, April/May issue of Handloader Magazine.
In his AR, the Hornady Match factory ammo averaged a little better than I saw but the Hornady Black was much worse for him: "Hornady Black 105 BTHP factory ammunition 2.35 inches and Hornady Match 108 ELD Match 1.05 inches." I was getting 1.5" to 1.75" 100 yard groups with the Hornady Black. Not great for me, and 2.35" is pretty bad.
He considers anything less than an inch group size to be exceptional for an AR. His various AR loads achieved from .91" down to .59" 100 yard groups. In comparison, from my loads I'm getting slightly better groups now but essentially in the same ballpark.
In his MPA bolt gun, he shot some pretty amazing groups:
"Berger’s 109-gain Long Range Hybrid Target bullet produced the tightest groups of the bolt-rifle test – .26- and .13-inch groups using 25.5 and 26.5 grains of IMR-8280 XBR"
Thus far, this is the best article I've read regarding loading this caliber. Well worth the read.
it has 2 flyers, but in the middle are 8 shots there, and it was 300.
but, i was not able to replicate it exactly like that anymore. and in those it was a hand picked brass, uniformed primer pockets and rest of prep voodoo done.
plus, probably, a glitch in the universe`s probability engine.
but, it happened.
That 300 yard group is Hollywood level stuff, but you did it without CGI.look better for my post #68 for amazing.
it has 2 flyers, but in the middle are 8 shots there, and it was 300.
but, i was not able to replicate it exactly like that anymore. and in those it was a hand picked brass, uniformed primer pockets and rest of prep voodoo done.
plus, probably, a glitch in the universe`s probability engine.
but, it happened.
I think my all time best is ~.12" with the 6.5 Manbun AR, but that was at 100. More crap can happen to mess up your groups at 300. For that group I did similar level voodoo prep that I have no interest in repeating for every outing- necks turned, primer holes prepped, cases sorted by weight then checked for volume, bullets sorted, etc. If I ever get to the point that I can't physically shoot the type of matches I like, maybe I'd get into the BR stuff. For now, I just dabble in it to see what I can get from a given platform.same here, no interest of doing it.
i got some new alpha brass i did not get to 300 yet. a 100 result was typical, but, it is not telling much of how it will spread flying further.
that is 5 below there, but at a 100. not exactly a smooth same hole... but no voodoo prep neither, just an accurate powder drop.
i had some other guy at 300yds line that day - he told me i should frame it, but i threw it away.
i think after barrel sped up it lost a bit of that initial accuracy, and i never loaded it again above 31gr, as it pushes primer out and destroys the pocket.
plus pushes brass shavings into the ejector hole - way too much pressure. no clue how on some forums people claim to load those dashers with above 32gr - it is definitely not for my gun.
i did not shoot it since 12/08/22 - so, probably time to try it out again.
Finally obtained the chronograph data for my 6 ARC loads. I have the higher end version of the MagnetoSpeed, which gives pretty accurate data. The downside is that via hanging off the end of the barrel it can open up the groups a bit so one should evaluate group size without it strapped on. Here are the results:
6.5 ARC Berger 105 BT 28.8 gn 2520
Series 25 Shots: 5
Min 2725 Max 2745
Avg 2734 S-D 9.5
ES 20
6.5 ARC Berger 105 BT 29.0 gn 2520
Series 24 Shots: 5
Min 2735 Max 2746
Avg 2739 S-D 4.8
ES 11
6.5 ARC Berger 105 BT 29.2 gn 2520
Series 23 Shots: 5
Min 2772 Max 2797
Avg 2781 S-D 9.6
ES 25
6.5 ARC Berger 105 BT 27.5 gn Varget
Series 26 Shots: 5
Min 2653 Max 2675
Avg 2665 S-D 8.6
ES 22
29.0 grains of 2520 was already my favorite load based on group sizes and the very low SD and ES validate that. Even with the MagnetoSpeed mounted that group size was 0.59 MOA. The other 2520 loads were just over an inch, so roughly 1 MOA. IMHO the velocity is great considering it is an AR. The average 2739 fps is only ~11 fps slower than the Hornady bolt gun 6 ARC data.
What was interesting is that the Varget SD and ES was similar to the other 2520 data, but the group size for the Varget was about 2.5X larger (it sucked).
Wind was gusting to 15 mph and was a factor in the group sizes.
6.5 ARC Berger 105 BT 28.8 gn 2520
Series 25 Shots: 5
Min 2725 Max 2745
Avg 2734 S-D 9.5
ES 20
6.5 ARC Berger 105 BT 29.0 gn 2520
Series 24 Shots: 5
Min 2735 Max 2746
Avg 2739 S-D 4.8
ES 11
6.5 ARC Berger 105 BT 29.2 gn 2520
Series 23 Shots: 5
Min 2772 Max 2797
Avg 2781 S-D 9.6
ES 25
6.5 ARC Berger 105 BT 27.5 gn Varget
Series 26 Shots: 5
Min 2653 Max 2675
Avg 2665 S-D 8.6
ES 22
29.0 grains of 2520 was already my favorite load based on group sizes and the very low SD and ES validate that. Even with the MagnetoSpeed mounted that group size was 0.59 MOA. The other 2520 loads were just over an inch, so roughly 1 MOA. IMHO the velocity is great considering it is an AR. The average 2739 fps is only ~11 fps slower than the Hornady bolt gun 6 ARC data.
What was interesting is that the Varget SD and ES was similar to the other 2520 data, but the group size for the Varget was about 2.5X larger (it sucked).
Wind was gusting to 15 mph and was a factor in the group sizes.
Very interesting that 2520 groups better for you than varget, I think it is a rather unusual trend. But, whatever works.
Varget load for you should have been close to 30gr, with a bit of a crunch.
I tested my alpha brass 3 days ago at 300, an sd was good, around 6, but groups were nothing to talk about. I think it was my fundamentals slipping off, again. Red square is an 1moa
Varget load for you should have been close to 30gr, with a bit of a crunch.
I tested my alpha brass 3 days ago at 300, an sd was good, around 6, but groups were nothing to talk about. I think it was my fundamentals slipping off, again. Red square is an 1moa
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As I reached closer to 30 gr the Varget was still giving flyers for ~1.5" groups that could have been much smaller. As mentioned, the recoil impulse felt a little harsher and the brass was more randomly distributed. I was using the same careful loading technique for the Varget as for the 2520 load with the 4.8 SD and 11 ES.
I tried some Berger 105 VLD's and found that a reasonably close jump made them way longer than magazine length. Not that I was expecting great results from such a big jump to the lands, but LOL the mag length VLD's were spraying ~4" groups. Standard BT bullets may not have quite the BC as VLD's etc. but they are accurate at mag length. I'm getting slightly better velocity than I expected, so that compensates for a bit.
I had such good results with the 2520 in my M14 that I've started using it for .308, though I'll still use Varget sometimes if I am well stocked with jugs of it. TFB tested 2520 at temperature extremes during an evaluation vs. Varget and found 2520 to be reasonably temperature stable. Not Varget level, but not bad. I'm going to try 2520 in .223 vs. Benchmark. I don't like the way Varget meters for small cases like .223 and went to Benchmark for that.
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Brownells has barreled Howa mini actions on sale in 6 ARC for anybody interested
www.brownells.com
It’s a drop in for a JTAC Industries chassis.
HOWA M1500 Mini 6mm ARC BL HB 20" T/C 5/8x24 3PS SKU: 430102218 | Brownells
Check out the HOWA M1500 Mini 6mm ARC BL HB 20" T/C 5/8x24 3PS SKU: 430102218 available Online at Brownells Today and many more Rifle Receivers & Parts products are available in our Gun Parts Department.
www.brownells.com
It’s a drop in for a JTAC Industries chassis.
Good stuff. Wish they had it in a 24" or 26" barrel.Brownells has barreled Howa mini actions on sale in 6 ARC for anybody interested
HOWA M1500 Mini 6mm ARC BL HB 20" T/C 5/8x24 3PS SKU: 430102218 | Brownells
Check out the HOWA M1500 Mini 6mm ARC BL HB 20" T/C 5/8x24 3PS SKU: 430102218 available Online at Brownells Today and many more Rifle Receivers & Parts products are available in our Gun Parts Department.
It’s a drop in for a JTAC Industries chassis.
View attachment 756964
Regarding 6mm ARC and flat shooting: That 11 fps ES I get with my favorite load translates to a 0.1" difference in drop at 200 yards from one extreme to the other. Variance from the mean will of course be ~0.05", so essentially nothing. At 1,000 yards impacts will be plus or minus ~2" in elevation. Variance in windage from the mean is only left or right 0.3". Should be able to hang a 6" plate at 1,000 and ding it all day, no?
![[rofl]](/xen/styles/default/xenforo/smilies.vb/013.gif "ROFL [rofl]")
Besides the nice flat shooting characteristics of 6 ARC, it carries much more energy at distance. I checked calculations against my typical .223 Service Rifle loads (Nosler cc 77's) that have essentially the same muzzle velocity as my 6 ARC 105's. At 1,000 yards the 6 ARC carries ~2.3X more energy than does the .223. Also the .223 went transsonic about a hair past 800 yards. The difference in drop is huge. I can see why some elements of the .mil would have been interested in this performance.
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