Grendel to ARC Brass

[BassinDmax]

I'm still a couple months out on my barrel, but I've been trying to purchase all the reloading components I'll need. I didn't want to keep holding out for ARC brass so I picked up 300 pieces of Lapua 6.5 Grendel brass. With there being some differences in the shoulder from Grendel to ARC, my question is, when I size this brass to 6MM ARC how far do I push the shoulder back?

[CZ527 Guy]

Without something to use as a comparator you are only guessing. If you have a head space gauge you can perhaps come up with a bushing that fits over the neck, allowing the bushing to stop pn your shoulder. Then measure a reference distance from the base of your case to the opposite end of the bushing that contacts the shoulder that establishes your head space. All this is assuming you have a caliper and are comfortable using it.

If this works out for you you can also use the same bushing to reference your Go- head space gauge. Id shoot for .004 clearance give or take .002".

Another option is a case gauge or a comparator neither will do you much good without a head space gauge or fired case for comparison.

https://www.whiddengunworks.com/product/case-gauge-3/

https://www.whiddengunworks.com/product/...ump-gauge/

How precise do you wish to get? for your consideration a Whiddnen click adjustable full length bump die.

https://www.whiddengunworks.com/product/...ing-kit-2/

[Bill]

make sure you anneal the Grendel brass, trim the FLS grendel brass back to 1.483 and run the Arc dies

[StoneHendge]

When I started on my 400 pieces, I bumped 5 back to SAAMI minimum of 1.183 base to B comparator line. Used them for my initial function check and then was able to use the fired measurement for sizing the rest. If you size all of them down to SAAMI minimum, you would possibly be subjecting your brass to unneeded stretch, but any virgin ARC brass would also be at SAAMI minimum (or below) - as would any brass in factory ammo. In my case, my Lilja chamber is 1.188 and I bump them to 1.185, so if I had bumped them all to 1.183, it wouldn't have had an impact on my brass life.

While you ponder that, fire up the trimmer! Your going to need to take 0.03" off and take them down to 1.480" OAL, and you should do this before you bump down since the longer Grendel brass could hit the top of your die. It did with my Hornady die and I lost a couple to dimples on the shoulder.  The trimming is the vast majority of the work. You could/should do your chamfering/deburring too. After that it's just a quick lube on the shoulder and inside/outside of the neck and through the sizer.

[Dino11]

make sure you anneal the Grendel brass,  trim the FLS grendel brass back to 1.483 and run the Arc dies

I anneal my brass, then size it, then trim it. This way you get a true sized case because the length will change when you bump the shoulder back. Never had a problem doing them this way.

I also pull my decapping pin out of the sizing die.

[grayfox]

If I read correctly, he does not have his barrel yet. So, like stonehenge says, trim all to the 1.480, then take maybe, 10, shoulders down to 1.183 as necked down cases. When the barrel comes in, you’ll be gtg with 10 to test with. This of corse assumes you have the hornady case comparator and B (0.350) insert, along with calipers. Additionally I’d keep on the lookout b/c you can still find a box or 2 or 3 of the 105’s and add them to your stash.

[grayfox]

As in... look at midwayusa, they have $33/box limit 5, as of this post.

[Dino11]

When I started on my 400 pieces, I bumped 5 back to SAAMI minimum of 1.183 base to B comparator line. Used them for my initial function check and then was able to use the fired measurement for sizing the rest. If you size all of them down to SAAMI minimum, you would possibly be subjecting your brass to unneeded stretch, but any virgin ARC brass would also be at SAAMI minimum (or below) - as would any brass in factory ammo. In my case, my Lilja chamber is 1.188 and I bump them to 1.185, so if I had bumped them all to 1.183, it wouldn't have had an impact on my brass life.

While you ponder that, fire up the trimmer! Your going to need to take 0.03" off and take them down to 1.480" OAL, and you should do this before you bump down since the longer Grendel brass could hit the top of your die. It did with my Hornady die and I lost a couple to dimples on the shoulder.  The trimming is the vast majority of the work. You could/should do your chamfering/deburring too. After that it's just a quick lube on the shoulder and inside/outside of the neck and through the sizer.

I guess it is possible for the neck to hit the top of the die... but it doesn't. I sized a Hornady ARC case, checked it for measure, then sized a Hornady Grendel checked it for size. I got the exact same reading on both. I also checked my die and the neck was a good ways from topping out, hence removing the decapping pin I could see down there pretty well and used my bent paperclip for checking cases to feel around in there. I think I would have seen shoulder or neck damage if it was hitting. I think were ok resizing Grendel brass in a Hornady die. At least my die is ok. But I will try your method as I have done it to other brass I resized, but the Grendel case is barely being moved and trimmed very much.

[BassinDmax]

Without something to use as a comparator you are only guessing. If you have a head space gauge you can perhaps come up with a bushing that fits over the neck, allowing the bushing to stop pn your shoulder. Then measure a reference distance from the base of your case to the opposite end of the bushing that contacts the shoulder that establishes your head space. All this is assuming you have a caliper and are comfortable using it.

If this works out for you you can also use the same bushing to reference your Go- head space gauge. Id shoot for .004 clearance give or take .002".

Another option is a case gauge or a comparator neither will do you much good without a head space gauge or fired case for comparison.

https://www.whiddengunworks.com/product/case-gauge-3/

https://www.whiddengunworks.com/product/...ump-gauge/

How precise do you wish to get? for your consideration a Whiddnen click adjustable full length bump die.

https://www.whiddengunworks.com/product/...ing-kit-2/

Might have helped to provide more info with my question, yes I'm new to the ARC and re-forming a different case to the ARC, but I'm not new to reloading. I'm far from an expert, but do have a good understanding of headspace and it's impact on reloading and case life. I have the Hornady Comparator and very comfortable with it's use and the use of calipers. I usually make my own modified case's, but I bought a Hornady modified case in the absence of a fired case to work with. I also have a Wilson Case Gage for the ARC. I pretty much have everything I need minus the barrel. I have the Hornady die set for the ARC and also purchased a Wilson full length bushing die. My plan is to use the Hornady full length die to form the brass and then use the bushing die to set next tension on successive reloads.

Based on the tools I have, can I bump the shoulder, without over-sizing, until it goes smoothly in and out of the case gage? If I did this on about 10 cases to start with and then fired formed them I would then have fired case dimensions for my barrel? Or should I wait for the barrel and insure they'll cycle properly before fire forming?

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make sure you anneal the Grendel brass,  trim the FLS grendel brass back to 1.483 and run the Arc dies

Even on new Lapua brass that's been annealed by the factory? I do anneal all my brass after every firing, but wasn't sure I needed to do it on Lapua brass prior to forming.

---

When I started on my 400 pieces, I bumped 5 back to SAAMI minimum of 1.183 base to B comparator line. Used them for my initial function check and then was able to use the fired measurement for sizing the rest. If you size all of them down to SAAMI minimum, you would possibly be subjecting your brass to unneeded stretch, but any virgin ARC brass would also be at SAAMI minimum (or below) - as would any brass in factory ammo. In my case, my Lilja chamber is 1.188 and I bump them to 1.185, so if I had bumped them all to 1.183, it wouldn't have had an impact on my brass life.

While you ponder that, fire up the trimmer! Your going to need to take 0.03" off and take them down to 1.480" OAL, and you should do this before you bump down since the longer Grendel brass could hit the top of your die. It did with my Hornady die and I lost a couple to dimples on the shoulder.  The trimming is the vast majority of the work. You could/should do your chamfering/deburring too. After that it's just a quick lube on the shoulder and inside/outside of the neck and through the sizer.

Good points, I'll start with about 10 cases at most. Thanks for the heads up on trimming, I'll pull out the old RCBS trimmer and trim them all to 1.480". I normally use the WFT2 to trim, however don't have the Grendel insert. I guess after trimming a few my arm will tell me if I need to order the Grendel insert

[BassinDmax]

make sure you anneal the Grendel brass,  trim the FLS grendel brass back to 1.483 and run the Arc dies

I anneal my brass, then size it, then trim it. This way you get a true sized case because the length will change when you bump the shoulder back. Never had a problem doing them this way.

I also pull my decapping pin out of the sizing die.

Thanks, I follow the same process you do with my fired cases. I also start with a Mighty Armory universal decapper and use no decap pin in my size die

---

If I read correctly, he does not have his barrel yet.  So, like stonehenge says, trim all to the 1.480, then take maybe, 10, shoulders down to 1.183 as necked down cases.  When the barrel comes in, you’ll be gtg with 10 to test with.  This of corse assumes you have the hornady case comparator and B (0.350) insert, along with calipers.  Additionally I’d keep on the lookout b/c you can still find a box or 2 or 3 of the 105’s and add them to your stash.

Correct, no barrel yet. Good point to trim first and no more then 10 cases. I do have the comparator and .350 insert.

[mkihne]

I'm still a couple months out on my barrel, but I've been trying to purchase all the reloading components I'll need. I didn't want to keep holding out for ARC brass so I picked up 300 pieces of Lapua 6.5 Grendel brass. With there being some differences in the shoulder from Grendel to ARC, my question is, when I size this brass to 6MM ARC how far do I push the shoulder back?

Is this for an AR15 or a bolt gun, or bolt upper for AR15 lower? My prep would be different for each.
I am waiting for bolt upper for AR and will be shooting with both. Most in this thread I would apply to a typical bolt gun head spacing, ultimately using fired cases for ongoing reloading. Without barrel in hand, what to do? 
I will use lapua cases for 6.5 grendel when available for bolt upper(Uintah). I will likely use Hornady cases for the AR. Currently, I only have about 20 fired cases(Hornady). I will consider some of these sacrificial cases. I purchased a Wilson “case checker” which can assess whether or not a case is within SAMMI specs.

I slightly undersized a fired case in a RCBS small base sizing die with the expander ball in place.
I put the case in the Wilson gauge and turned in the die and resized until the headspace part of the die showed the case was within spec. I then trimmed the case neck until it was even with the minimal SAMMI part of the gauge.

This gives me a case that should fit even a tight chamber due to small base die. I will fire in AR15 barrel. When I get my Hornady dies, I will do the same procedure for initial firing in the bolt gun, using the small base die only if necessary. I will get a custom die for the bolt gun when I have fired cases to send.

I will likely use commercial die for the AR. More generous setback to AR shoulder vs 2 thou or so for bolt gun.JMO

[StoneHendge]

Dino, the neck of Grendel brass doesn't hit the top of YOUR Hornady die. For it to not hit the top of MY Hornady die also, Hornady would need to manufacture a consistent product. We can consider this to be another example of how they don't. This is what a few pieces of my brass looked like when I didn't trim first. 

   

[Old Bob]

I resized AA, once fired Hornady & Lapua 6.5 Grendel to 6mm ARC. I sized some in a Hornady die & some in a Wilson bushing type full-size die. With the cases sized in the Hornady die, I was able to trim all the cases with my RCBS trimming tools. With the cases sized in the Wilson bushing die, I was able to trim only the AA cases. The trimmer pilot wouldn't fit in the Hornady & Lapua cases. I had to re-run those cases through the Hornady die before I could trim them.

Apparently the bushing I had in the Wilson die sized the necks too small. I changed the bushing to a larger diameter & that fixed the problem there.

Observations about the process: All three brands of cases have different case neck thicknesses with Lapua the thickest, Hornady in the middle & AA cases the thinnest. Thusly, all three brands will probably have different case neck tensions when bullets are seated. Outside case neck diameters will certainly be different.

A bushing type die will mitigate the tension problem somewhat but there are still problems using different brands of brass. Case capacity being the number one difference. What are the chances identical components loaded in each case brand will give the same down-range results?

This all part of the fun of reloading... figuring out what works & what doesn't.

[skyrep]

Old Bob,
I found that when I use the Wilson Busing sizing die, I had to use a specific size bushing for a specific type Brass. I.E.: Hornady: .266 bushing, Lapua: .268 bushing. That would get me a certain tension that I wanted.
i'm shooting from a Savage 10 Bolt Gun.

[Dino11]

Old man Bob gets it...

What worked for me may not work for you, there are to many variable that come into play in the reloading process.
Just like with load development, there is no gospel that says again what worked for me may....

We have to make sacrifices when reloading, yours was a case with a dented shoulder so you needed to find a work around to fix the issue.

The way you are doing it is not wrong, nor is the way I am doing it either.
The lesson learned here is that if I ever run into the same problem I have to look at it and come up with a solution just as you did. Because of what happened to you I now have information made available to me through your pearls of resizing a Grendel case to 6 ARC.

It's just like politics... Their are no definitive rules to the game, we make our own rules to fit our agenda.

[grayfox]

Bassin, yeah, the short version for me is to trim/bump/trim etc as needed in order to get your 10 cases to (Saami specs) --> 1.480-490 length (1.480-85 preferred) and 1.183-190 (1.180-83 preferred) shoulder with your comparator "B" insert. My reasoning: you are just starting out, this is the size that a vendor would make so as to "fit" its commercial ammo in all chambers, and once you get your pipe and can fire and compare, this will get you started. I'm saying to basically mimic what a mfr would do in making its ammo for you. Once you have all your rifle assembled then you can zero in on what you want to do with fire forming the rest.

In my world I try to keep things simple if I can. Then improve from there.

[BassinDmax]

I'm still a couple months out on my barrel, but I've been trying to purchase all the reloading components I'll need. I didn't want to keep holding out for ARC brass so I picked up 300 pieces of Lapua 6.5 Grendel brass. With there being some differences in the shoulder from Grendel to ARC, my question is, when I size this brass to 6MM ARC how far do I push the shoulder back?

Is this for an AR15 or a bolt gun, or bolt upper for AR15 lower? My prep would be different for each.
I am waiting for bolt upper for AR and will be shooting with both. Most in this thread I would apply to a typical bolt gun head spacing, ultimately using fired cases for ongoing reloading. Without barrel in hand, what to do? 
I will use lapua cases for 6.5 grendel when available for bolt upper(Uintah). I will likely use Hornady cases for the AR. Currently, I only have about 20 fired cases(Hornady). I will consider some of these sacrificial cases. I purchased a Wilson “case checker” which can assess whether or not a case is within SAMMI specs.

I slightly undersized a fired case in a RCBS small base sizing die with the expander ball in place.
I put the case in the Wilson gauge and turned in the die and resized until the headspace part of the die showed the case was within spec. I then trimmed the case neck until it was even with the minimal SAMMI part of the gauge.

This gives me a case that should fit even a tight chamber due to small base die. I will fire in AR15 barrel. When I get my Hornady dies, I will do the same procedure for initial firing in the bolt gun, using the small base die only if necessary. I will get a custom die for the bolt gun when I have fired cases to send.

I will likely use commercial die for the AR. More generous setback to AR shoulder vs 2 thou or so for bolt gun.JMO

This is a gas gun, I'll be running a 20" X Caliber barrel. I like you method plan, I think this will work in my situation also.

[BassinDmax]

Bassin, yeah, the short version for me is to trim/bump/trim etc as needed in order to get your 10 cases to (Saami specs) --> 1.480-490 length (1.480-85 preferred) and 1.183-190 (1.180-83 preferred) shoulder with your comparator "B" insert.  My reasoning: you are just starting out, this is the size that a vendor would make so as to "fit" its commercial ammo in all chambers, and once you get your pipe and can fire and compare, this will get you started.  I'm saying to basically mimic what a mfr would do in making its ammo for you.  Once you have all your rifle assembled then you can zero in on what you want to do with fire forming the rest.

In my world I try to keep things simple if I can.  Then improve from there. 

Yes, makes perfect sense and I strive for the KISS method also, however sometimes I veer off the road when I see something shiny I think you all helped me get on the right track when I tackle my Grendel cases.