Grendel to ARC, frustrated.

[KMW 1954]

This is the third time I've sized down 6.5 Grendel to 6ARC. The first time went well other than I found out not to anneal before I resized it. Last batch I ran into a problem with pierced primers and hard extraction.

This time after processing 30 pcs I loaded a couple pcs and tried chambering it. No go! So I went thru it all again and all put two pcs sat all the way down into my Hornady case gage. Then I tried chambering raw brass into the gun, no problems, with feeding or extraction.

From there I loaded 2 more and they wouldn't seat into the gage, neither would they chamber in the gun.

Checked everything again, case length, comparator measurement, BTO, neck measurements. All measured the same as the 6ARC loaded Hornady brass. Stumped.

Finally started pushing back the bullet, as that was all I could come up with. Pushed it back .045" from where I was normally seating this bullet and now it chambers? WTH? Been loading and shooting this gun for over a year. Now wanted to try the Grendel brass as I've acquired a good bit of it.

 

[Oso]

You are necking down cases, which means thickening the neck wall thickness. In addition, the 6ARC has a shorter case (body) so you are bumping back the shoulder, which means that some of the 6.5 Grendel’s shoulder material (typically thicker) is now being converted into the lower portion of the newly formed neck on the converted 6ARC cases. This is the perfect setup for forming a Doughnut. This would explain the pressure spike and hard bolt lift that you are experiencing when using converted 6.5 Grendel cases.

>What is the Neck O.D. of your newly converted 6ARC?
>What is the Neck O.D. of the newly converted case after seating a bullet in it?
>What is Neck O.D. of store-bought Factory 6ARC Ammo that has been fired through this rifle?

How do these numbers compare???

The metallurgy of the brass may also contribute to springback (trying to return to 6.5 Grendel dimensions). What is the headstamp on the Grendel Brass?

 

[KMW 1954]

OK, makes sense but doesn't explain why seating the bullet deeper corrected the bolt not closing. As for the Factory numbers. This rifle hasn't seen a Factory round since the first week it was shot over 18 months ago.

 

[SeabeeKen]

Sounds like you were jamming the bullet into the riflling or between a donut and rifling.
When reforming, hold the case in the die for 5 seconds to allow it to adjust and settle into its new shape. Works for me

 

[KMW 1954]

Sounds like you were jamming the bullet into the riflling or between a donut and rifling.
When reforming, hold the case in the die for 5 seconds to allow it to adjust and settle into its new shape. Works for me

Had loaded this same bullet out to the original length before while using 6ARC brass. Standard practice id to load slow. Not a race when trying to load Match use ammo.

These bullets are 105gr Hornady loaded light to fire form this brass. Thankfully I haven't processed a bunch of this stuff. So if it tuns into this much trouble I'll find something else.

 

[Bronsin]

If you decide to try something else, get some Alpha 6PPC brass, load the bullet into the lands, fireform it and be done with it.

 

[WyleWD]

If you decide to try something else, get some Alpha 6PPC brass, load the bullet into the lands, fireform it and be done with it.

Or even easier.... buy some Alpha or Peterson 6ARC brass (or both). Load it And just go shooting. In the end it's cheaper and MUCH less frustrating. JME. WD

 

[SeabeeKen]

Had loaded this same bullet out to the original length before while using 6ARC brass. Standard practice id to load slow. Not a race when trying to load Match use ammo.

These bullets are 105gr Hornady loaded light to fire form this brass. Thankfully I haven't processed a bunch of this stuff. So if it tuns into this much trouble I'll find something else.

I reformed some grendel into ppc and found that my die would only bump the shoulder barely enough to get a tight bolt closure. I was moving the shoulder back into the thicker body brass

 

[Oso]

As others have mentioned, buying factory 6ARC brass is the easy answer.

Just out of curiosity - How are you doing the initial case conversion?
Are you simply running 6.5 Grendel case into 6ARC FL Die? Are you using the expander ball or remove it? When annealing did you make certain to anneal a portion of the 6.5 Grendel case body as well?

 

[dellet]

First thought is stop using a caliper to do any serious measuring. Because if everything measures the same, and one fits but the other doesn’t, it’s not the same.

Carefully check the case mouth. What may be happening is that the edge has a slight flare and it’s not setting the bullet deeper that is correcting the problem, it’s the repeated chambering, or if the sizing die has a crimp feature that rolled edge is wearing off. A more aggressive de burr and chamfer is worth a try.

Marking the case to find where it’s rubbing won’t hurt.

I have found when reforming brass from another cartridge it’s worth it to screw the die down a half turn from the previous setting so the brass can properly fire form. It won’t form the same in the die as it does in the chamber. So if your die is set up to resize fired brass minimally, trying to form a virgin case from a larger cartridge at the same setting is asking for trouble. In theory, the case wants to return to its original shape. With factory brass for the cartridge, that would be to smaller than fired. With reformed new brass, it wants to return to larger than sized. That might help stop some of the frustration you’re finding.

One other thing to check is for the dreaded donut at the base of the neck, and the transition from boat tail to bearing surface on the bullets, pressure ring. Not uncommon for the bullet to be slightly larger diameter for a few thousandths at that point. If your die have a slight donut on the inside where you can’t measure easily, the diameter on the loaded round will change when it slips below the neck.

 

[Rob01]

Why? Plenty of good brass for the ARC. Just go buy some and use it and make your life easier with less stress and frustration.

 

[KMW 1954]

Why? Plenty of good brass for the ARC. Just go buy some and use it and make your life easier with less stress and frustration.

Thanks again to everyone that has responded!

This response, along with those like it, states it best. Why?

Mostly because I wanted to see if I could do it as others have suggested. Also, because as I admit, I am CHEAP! I work at a very large outdoor range and the stuff for me is free to pick up. Though not that I need it. I still have 100pcs of brand new Starline brass that has not been loaded, as I am still working with the 1st 100 pcs I have.

Now after sleeping on it, this is more and more looking like a fool's errand. But once again you all have come through and provided excellent suggestions. I will still investigate those. Thanks.

 

[SKWERLZ]

This is the third time I've sized down 6.5 Grendel to 6ARC. The first time went well other than I found out not to anneal before I resized it. Last batch I ran into a problem with pierced primers and hard extraction.

This time after processing 30 pcs I loaded a couple pcs and tried chambering it. No go! So I went thru it all again and all put two pcs sat all the way down into my Hornady case gage. Then I tried chambering raw brass into the gun, no problems, with feeding or extraction.

From there I loaded 2 more and they wouldn't seat into the gage, neither would they chamber in the gun.

Checked everything again, case length, comparator measurement, BTO, neck measurements. All measured the same as the 6ARC loaded Hornady brass. Stumped.

Finally started pushing back the bullet, as that was all I could come up with. Pushed it back .045" from where I was normally seating this bullet and now it chambers? WTH? Been loading and shooting this gun for over a year. Now wanted to try the Grendel brass as I've acquired a good bit of it.

That’s a ton of shoulder to push back, the grendle brass works a lot better for 22ARC as it’s the same headspace.

Necks need trimmed back and/or thinned?

 

[Rob01]

Thanks again to everyone that has responded!

This response, along with those like it, states it best. Why?

Mostly because I wanted to see if I could do it as others have suggested. Also, because as I admit, I am CHEAP! I work at a very large outdoor range and the stuff for me is free to pick up. Though not that I need it. I still have 100pcs of brand new Starline brass that has not been loaded, as I am still working with the 1st 100 pcs I have.

Now after sleeping on it, this is more and more looking like a fool's errand. But once again you all have come through and provided excellent suggestions. I will still investigate those. Thanks.

You are talking to the original cheap guy but at some point I realized that my time and stress level are worth more than saving $50. More time to shoot than sitting in the loading room trying to make one thing out of another.

 

[KMW 1954]

Just out of curiosity - How are you doing the initial case conversion?
Are you simply running 6.5 Grendel case into 6ARC FL Die? Are you using the expander ball or remove it? When annealing did you make certain to anneal a portion of the 6.5 Grendel case body as well?

The first time I tried this I annealed first and was collapsing the case shoulders do then O tried un-annealed.

That first batch of 20 or so worked very well. no problems. Second batch developed pierced primers and tight bolt extraction. This batch, bolt will not close on a loaded round but will close on a resized empty case.

FL sizing with the ball in place using a Lee FL die.

Was a nice exorcise but I think I learned what I needed. Which is Don't bother!

 

[SKWERLZ]

The first time I tried this I annealed first and was collapsing the case shoulders do then O tried un-annealed.

That first batch of 20 or so worked very well. no problems. Second batch developed pierced primers and tight bolt extraction. This batch, bolt will not close on a loaded round but will close on a resized empty case.

FL sizing with the ball in place using a Lee FL die.

Was a nice exorcise but I think I learned what I needed. Which is Don't bother!

Yea, pushing that shoulder back 30 thousandths and dealing with the resulting issues is a lot of hassle.

That’s one of the reasons I chose 22 arc over 6 arc.
So I can use cheap grendle brass.

 

[rockhound78]

I gave up on Grendel brass also. Too much trouble/frustration, and just bought some Starline 6mm ARC brass

 

[Oso]

The first time I tried this I annealed first and was collapsing the case shoulders do then O tried un-annealed.

That first batch of 20 or so worked very well. no problems. Second batch developed pierced primers and tight bolt extraction. This batch, bolt will not close on a loaded round but will close on a resized empty case.

FL sizing with the ball in place using a Lee FL die.

Was a nice exorcise but I think I learned what I needed. Which is Don't bother!

A couple of suggestion for improving end result:
1) Buy factory 6ARC brass… sorry to easy to pass up

Case Conversion
2) Anneal case before initial sizing with the flame focused toward lower area of case shoulder so that annealing zone will be the bottom of neck through upper portion of body… all of the area that is going to be reformed and relocated.
3) For the initial case forming (first pass) use the FL Sizing Die (remove decapping rod & expander ball) to set back shoulder.
4) Use imperial Wax and give the case a nice thin coat.
5) Slow constant pressure on ram during forming.
6) 2nd pass through the FL Sizing die but this time with the Expander Ball installed back in die… make certain cases are still lubed adequately
Option: anneal 2nd time before sizing the neck to ensure desired “neck tension”
7) Neck Turn to desired wall thickness for your chamber clearance.
8) Trim & chamfer necks to desired length.

*** This is a lot of work and maybe necessary for certain cartridges …. But if there is a quality, commercially available factory case then it’s not worth the effort.

 

[tdogg]

When I first built my ARC, all I had was Grendel brass (ARC brass was unavailable). I just lubed it and sized virgin brass in my ARC die, trimmed it to length, and went shooting. No annealing until I fireformed it.

I still use Lapua Grendel brass in my ARC for precision loads. Everything else is either Hornady ARC or converted Grendel Starline.

Not sure why you had to shorten the OAL to get it to chamber? That is weird.

Cheers,
Toby