6mm arc maybe not that versatile.

[Texcl2]

[A5BLASTER]

Why not I run 85 grain 6.5mm bullets in a 7.5 twist grendel barrel just fine.

So I dont see why your light weight varmint 6mm bullets won't run from a 7.5 twist 6 arc pipe.

All it's going to do is make it have more spin. Not like your going to get enough velocity to make it separate the jacket from the core.

Folks been shooting the same thing for years as a 6mm grendel aka 6mmar and I know several guys shoot light weight stuff out of them.

[Lemonaid]

So far in my fast twist 1-7 6mm PPC RAP the most accurate bullet is the Sierra 60 grain HP. I will soon order a bunch of the low cost Speer 75 hp in anticipation of using them when Monster 20 ARC barrels are available.

Sierra 60 HP, H322 24.0, 2.080, Lapua 7.62, Fed 210
24.0 3003,2988,3004,3019,2993 .530 group SD 11.93 AVE 3001
24.0 3053,3049,3044,3048,2991 .740 group SD 25.91 AVE 3037

[Fess]

Feel free to correct me, but my understanding is that a major reason for the traditional preference of a "slow-as-possible twist" barrel was the inconsistent quality of bullets. IMO, that is less of an issue now. Years ago, Lijla barrels had an article (which I see has been updated) on this. When a bullet is slightly unbalanced, whether due to uneven thickness of the jacket or defects in the lead core, its actual center of rotation and center of mass will be slightly off. Other things, like the bullet being slightly misaligned or not obturating uniformly can also throw balance off. Since the bullet leaving the muzzle is spinning at high speed, it will literally jump to the side slightly as soon as it escapes the confines of the barrel. This, of course affects accuracy.

I found the updated article at Lilja : https://riflebarrels.com/a-look-at-b...nce-and-twist/

[windsage]

Sierra has said that they recommend that their bullets stay under 300,000 rpm to prevent any chance that the jackets fail. I normally run .224 x 75gr ELD's at 6.5:1 and 3,000 fps, which is about 330,000 rpm. I haven't had any issues. Eventually, if you were light enough, and had a high enough velocity, you might lose some rounds mid flight from jacket failure. Other than that, more spin can, as said above, effect your maximum achievable accuracy for benchrest type activities. I do not think a 6 arc is going to go fast enough to have any issues at 7.5:1.

[Texcl2]

[grayfox]

I was going to say, the faxon is 1:8 and running fine for me... but if you've already made your pick, go for it.
I'll be trying the 75 Vmax someday when I get some time.

[Texcl2]

[PGW Steve]

While not specific to the 6mm ARC, I do have some experience with extreme twists and bullet weight ranges. Over 20 years ago, I had a 6mm-284 with a 1/7 twist to shoot Sierra 107's at 3250 IIRC. I was going on a varmint hunt in Nebraska, and worked up a load with 70 grain Nosler BT's. I managed to push those at 4100 or so, and none of them came apart. Accuracy for both was around 1/2 MOA at 300 yards. Ever since that rifle, I've never had any fear about over spinning a bullet. Unless of course it's a light jacketed bullet and it flat out blue streaks. I don't think the ARC will have a problem with such a small powder charge compared to the 284 case.

[StoneHendge]

While not specific to the 6mm ARC, I do have some experience with extreme twists and bullet weight ranges. Over 20 years ago, I had a 6mm-284 with a 1/7 twist to shoot Sierra 107's at 3250 IIRC. I was going on a varmint hunt in Nebraska, and worked up a load with 70 grain Nosler BT's. I managed to push those at 4100 or so, and none of them came apart. Accuracy for both was around 1/2 MOA at 300 yards. Ever since that rifle, I've never had any fear about over spinning a bullet. Unless of course it's a light jacketed bullet and it flat out blue streaks. I don't think the ARC will have a problem with such a small powder charge compared to the 284 case.

The 70 Grain NBTVs are pretty devastating at 3k out of my 6x45 - I can't imagine them at 4100. Do you know how many grooves your rifling had? I think this comes into play with the centrifical force on the jacket as the bullet is spinning down a barrel. I'm not a physicist or engineer, but I think a jacket in a 6 groove barrel would hold up better than in something like a 3 groove BHW barrel where it could be slipping and/or deforming.

[SDguy]

If your primary goal is saving fur then a smaller caliber yet may be your goal. Coyotes fur hunters that are really out to preserve the pelt are often choosing a 17 cal. 17 Remingtion historically has been the preferred tool of the trade w the serious coyote pelt hunters. 17 Fireball has been a somewhat distant second. From my perspective the primary potential flaw w the 17 cal in recent years is the lack of preferred bullets for pelt hunting. 25 grain and 30 grain HP w a fine target tip were the go to pelt hunters bullet of choice. Unfortunately the availability of these fine bullets has largely dried up in favor of the plastic tip highly frangible options more recently.

If all you wish to do is dispatch the coyote your options are many. If you are striving to save pelts then smaller diameter well chosen bullets may be preferred.

[SDguy]

If it turns out you want a slower twist I'm confident you can order your barrel with the twist rate accordingly. Personally I would not consider a twist any slower than a 9 twist. Down side is factory ammo would then be pretty much off the table.

[tdbru]

Sierra has a warning on the box of 85gr. 6.5mm about being medium velocity or lower. forget off the top of my head, but i had them loaded as fast as safely possible in a 6.5x55 Win M70 with a twist of 1-7.87 according to the hang tag. and they came apart shortly after muzzle exit. not every time. but occasionally. So i kept them all now for my 6.5 Grendel and don't run them faster than what i can get out of my 6.5 Gr. I'd heard of very thin jacketed varmint bullets having jacket failure due to high rotational speed and always thought it an "urban legend" so to speak. until it happened to me a couple of times with that 6.5x55. The 6.5mm 85gr. Sierra works very well as a varmint bullet out of the Grendel so no complaints, i just use them in the 6.5 Gr.
-tdbru

[mel]

my monster 20 loves the lighter bullets I use 70 and 75g for varmints and coyotes one of my friends runs even lighter bullets out of his with no issues

[Laman]

I built my ARC primarily to use up the hundreds of custom benchrest bullets and related powders I have accumulated over the years. Bullet weights range from 59 to 68 grains and I have found minute-of-coyote accuracy out of all of them. i really don't feel the ARC case can get these weights of bullets up to enough velocity to worry about over spinning them even with a 7.5 twist.