21 inch Criterion barrel chambered by Precision Firearms, Aero receiver, bolt group, and adjustable gas block. Tried 105 gn and 90 gn bullets. AC 2560, and LeverEvolution powders workups. Gas block is now at full open and has been removed and checked a few times. I am using ASC 5 and 10 round magazines and also a 6.5 Bobsled single feed. The bolt has locked back maybe 3 times out of 300 or so rounds, Cases eject from 4 o'clock to 3 o'clock depending on powder load and gas block setting. Magazines and lower work fine on two separate rifle length 6.5 Grendel uppers and a rifle length .223. I also tried 2 other bolts from my Grendels and waxed the bolt contact areas in the upper. The bolt drops in easily and does not seem to be hanging on the gas tube. I am running out of ideas here and about ready to either enlarge the gas port (last resort), try a non adjustable gas block, get another lower and with a lighter buffer spring or pull the barrel and gas tube and install on another upper.

All suggestions welcome and thanks in advance

Jim

Oh and as a side note I ran into a buddy at the range who is having the same problem with his 6 ARC build. I have no idea what his build is but he is also a experienced AR builder. Is this a common problem with this cartridge?

I have a 6 mm ARC AR15 but using 6.5 Grendel brass necked down.  This rifle has  26” Bartlein barrel by Craddock and mainly used for steel out to 1,000yrds (once I get load development done).  The dies, FL neck bushing from L E Wilson, were over sizing down by .0075 vs my 223 by .003.  So I’m having Whitten make me custom dies to be more inline with SAAMI specs and about .0025 down from fired brass.  This should cut stress on the brass and better fit chamber.

Next inquirer is bolt questions.  I have the JP Grendel bolt so I think I have one of the best but still feel the bolt is the weak link for both Grendel and ARC.  The Grendel bolt face ID measures .4525 and the 223 measures .378 so the the wall thickness has been reduced by  about half.  Why isn’t the Grendel bolt face based on SAAMI spec like the 223?  What does your bolt face measure out to?

For you engineers and machines out there.  Can you add back the lost thickness of the bolt face wall to the OD of the bolt face and to the OD of the lugs?  Is there enough room to add those dimensions to the barrel extension? Would this bring the Grendel bolt strength back to a point that it could be considered safe at 60-62k psi capable platform?

Current OD for lugs is .740  Plus lost wall thickness of .0315 (x2)  (if you make bolt id .441 not .4525) would make lug od .803.  The current extension id is .830 should make enough clearance.

 Current bolt face OD is .5250 plus .0315 (x2) is .588.  plus needed clearance.

I think the extension can handle that change.

What are your thoughts?  This is just an exercise of what if to start with.

Cheers

Philip

Cleaned out the throat as per Pac-nor now no problem.

Did what CZ527 said in the other post , fixed mag feeding problem.  

But in the mean time I sent a fired brass to Copper Creek and got an OAL gauge and a 103ELD-X Bullet

Factory 103eld-x shows 2.24 on my caliper and the gauge measures my chamber at 2.26

Is that good , bad , or ?


and just to make sure of the hunt had my eyes checked (BAD) new glasses will be here in 10 days and cataract surgery is maybe 5 years away according to the Doc.

Precision Hunter Hornady 6MM ARC 103 GR ELD-X Ammo at Firearms Depot at a new lower price. Snatch it up quick, it won't last long ...

https://firearmsdepot.com/hornady-6mm-ar...%3D.SVp6VP

Still high but down from what they were . Just in time for deer hunting


https://ammoseek.com/ammo/6mm-arc

Bulk surplus powder similar to Ramshot Tac available at American reloading if interested. If interested don't forget the promo code - Land for the 20% discount.

Only 16 & 32 pounders available as of this posting.

Sportsman fulfillment .com just sent me an email, they have savage axis II's in 6 Arc, 3 flavors, including the heavy barrel one.  On sale $300-400.

Good way to get into one at lower costs...

Hello everyone,


I just found this forum, looking forward to reading and learning here. I built a 6mm ARC upper a couple of months ago using an 18" Odin Works barrel topped with an Arken SH4 6-24 scope.

Took my new cz out today did 40 rounds of Hornady 103 ELD-x 6ARC

I had 2 problems, Hope you guys can help with 

1st.   Very hard to work bolt after each shot. going forward with fresh round no problem very smooth and easy. After the shot it was hard to flip lever up and hard to pull back. Again this was with factory ammo.
This rifle was a 7.62x39 before barrel change and did not do this with that ammo.

2nd. I am using factory 7.62x39 Mag's both of the mags were hard to load and when using did not want to pick up a round after ejecting the fired round. worked ok with 2 rounds but started getting bad after 3 rounds in the mag.. I only hunt so 2 rounds work for me but I don't like something that doesn't work the way it should

This was a cz527 action with the pac-nor barrel . 

Thanks for any feed back on this

Brand: Shaw® Barrels

• 24" Savage Heavy Mag Contour
  

• 5/8-24 Muzzle Threads
  

• 1-7" Right Hand Twist
  

• Finished Headspace, Ready to Install