Running 6 ARC in a bolt. No plans for a gas gun or to reload. Will rely on the factory 80 to 108 loads. All the calcs reference 7 and 7.5 for my location and use. Has anyone here witnessed a hill of beans difference specifically with 6 ARC bolt guns and the 7 vs 7.5? Thanks!
6 ARC Twist Rate Experience With 22-24" Bolt Gun 7.5 vs 7
- Thread starter PEWPEWPEW
- Start date
I've never done anything besides 7.5" twist in my 24-28" match barrels and I've shot almost exclusively 109 ELD-M and 110 A-tips.
I see no reason to go to a 7" twist but I also don't think it would hurt anything really either. Not really the cartridge to push 115's and for anything under 110 it's a non-issue stability wise. Not powerful enough to spin anything apart really, either...
I see no reason to go to a 7" twist but I also don't think it would hurt anything really either. Not really the cartridge to push 115's and for anything under 110 it's a non-issue stability wise. Not powerful enough to spin anything apart really, either...
I push 115 RDF's in my 16" 6 ARC and it's a 7.5 twist. Shoots great. Pushing them 2,575 FPS MV with Hodgdon LeverEvolution powder and CCI 400's, too.
I've shot the 6mm ARC with 7.5 twist and 7 twist side by side.
Same match ammo, same barrel lengths, on the same day.
The Proof 7.5 twist first 5 shot group was 1/2" ...the BA 7 twist barrel was 2.5".
Big difference...but most likely had less to do with twist rate and more to do with barrel quality, and the fact that the BA barrel was part of a factory upper, and the Proof was an actual build, with accuracy efforts employed.
Same match ammo, same barrel lengths, on the same day.
The Proof 7.5 twist first 5 shot group was 1/2" ...the BA 7 twist barrel was 2.5".
Big difference...but most likely had less to do with twist rate and more to do with barrel quality, and the fact that the BA barrel was part of a factory upper, and the Proof was an actual build, with accuracy efforts employed.
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So I immediately scrapped the Areo upper with the 7 twist BA barrel and bought another 7.5 Twist Proof.
Which also shoots half in groups.
The 7 Twist is just a bare barrel, I even used the barrel extension for a 30 RAR project, along with all the other upper parts. So it wasn't a total loss.
Which also shoots half in groups.
The 7 Twist is just a bare barrel, I even used the barrel extension for a 30 RAR project, along with all the other upper parts. So it wasn't a total loss.
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That above has nothing to do with twist but of the barrel quality to reiterate what he said. Don’t take it for any useful info for your question OP.
I have a 7 twist 26” PVA Osprey barrel and it shoots factory ammo 1/2 moa and tighter with my hand loads. I also have a 22” AR with a 7.5 twist which I have only shot factory ammo through and it is solid in the 3/4 moa area but it’s an AR so the main reason it’s not as accurate as the bolt gun. So my answer is similar to others in that the 7 vs 7.5 will mean nothing with the ARC and the bullets you plan to use. Either in a quality barrel will work.
I have a 7 twist 26” PVA Osprey barrel and it shoots factory ammo 1/2 moa and tighter with my hand loads. I also have a 22” AR with a 7.5 twist which I have only shot factory ammo through and it is solid in the 3/4 moa area but it’s an AR so the main reason it’s not as accurate as the bolt gun. So my answer is similar to others in that the 7 vs 7.5 will mean nothing with the ARC and the bullets you plan to use. Either in a quality barrel will work.
I went from a 1:7 gas gun to a 1:7.5 Krieger bolt gun. Both shoot any factory ammo under 1” ignore the other groupings. Was trying to develop a load with Staball match and my rifle was not having it. Another good note is that Federal is releasing gold medal match 6arc using Berger 108s this year.
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I will be running a decently long barrel. I used my best "educated wish estimations" with all my planned OEM loads. I rand different temps etc etc.
Using the Berger SG stability calcs.
1:7 varies from 1.69 to 2.15 -- 1:7.5 varies from 1.47 to 1.87
Using the Berger SG stability calcs.
1:7 varies from 1.69 to 2.15 -- 1:7.5 varies from 1.47 to 1.87
I run 18" 7.5 twist in ARs and it stabilizes all the bullets from 58 gr to 115 gr DTAC.
So either twist rate 7.5 or 7 will stablize any 6 mm bullet available. I've shot 105, 107, 108, 110, 112, 115 gr bullets.
Thats the load data for 115 DTACs AR 15 6 mm ARC 7.5 twist Proof, it likes most of the 107s, 108, 110 and 115 are it's best bullets.
Remember between these two twist rates there is nothing to be concerned about...at all...more important is the quality of the barrel, the chambering job, and all the things that make a premium barrel accurate. The 6 ARC in a AR 15 will shoot alot of 1/4" 3 shot groups and most 5 shot groups around a half inch or less.
A close up shows how many times the bullet just enlarges the hole.
The 6 ARC is very accurate. This happens to be a Proof 7.5 twist...but a 7 twist with any premium brand will do.
No need for arguments.
Bore scope it., tapper lapp, get the burrs off the gas port, true reciever, polish feed ramps, center bolt carrier, glue in barrel, tighten barrel nut to 60 ft/ lbs, no more no less, although some start torque accuracy at 45 to 48, not me.
I mill a channel in the barrel nut if it doesn't align the gas tube at 60 ft/ lbs.
This is the important stuff, not the twist rate as long as its adequate for the heaviest, longest, bullet you intend to shoot at your altitude and lowest expected temperature...simple.
So either twist rate 7.5 or 7 will stablize any 6 mm bullet available. I've shot 105, 107, 108, 110, 112, 115 gr bullets.
Thats the load data for 115 DTACs AR 15 6 mm ARC 7.5 twist Proof, it likes most of the 107s, 108, 110 and 115 are it's best bullets.
Remember between these two twist rates there is nothing to be concerned about...at all...more important is the quality of the barrel, the chambering job, and all the things that make a premium barrel accurate. The 6 ARC in a AR 15 will shoot alot of 1/4" 3 shot groups and most 5 shot groups around a half inch or less.
A close up shows how many times the bullet just enlarges the hole.
The 6 ARC is very accurate. This happens to be a Proof 7.5 twist...but a 7 twist with any premium brand will do.
No need for arguments.
Bore scope it., tapper lapp, get the burrs off the gas port, true reciever, polish feed ramps, center bolt carrier, glue in barrel, tighten barrel nut to 60 ft/ lbs, no more no less, although some start torque accuracy at 45 to 48, not me.
I mill a channel in the barrel nut if it doesn't align the gas tube at 60 ft/ lbs.
This is the important stuff, not the twist rate as long as its adequate for the heaviest, longest, bullet you intend to shoot at your altitude and lowest expected temperature...simple.
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I have a 1:7 but not in bolt action. In general the 1:7 will start chopping off some of the lighter end of the bullets available to shoot. This of course depends on the barrel length.
For me I never even considered shooting super light bullets at higher velocity so it's moot for me and 1:7 works great.
On the other hand 1:7 at least in theory can handle 115 grain bullets but I haven't tried it yet.
