can I use 220 Russian to make 6mm ARC brass?

[AndrewB]

I have 2 reamers on the way for a 6mm arc and a 22 arc. I shortened the free bore and will use short light bullets to shoot prairie dogs with from an AR platform. Doing this in the hopes of better accuracy and some speed increase over a 223. IMO, that is what this is good for. Don't really care about shooting big bullets slow.

Anyhoo, I have 800 new 220 Russian Sako cases laying around. Any opinions on whether I can run them thru a full length Arc die and load them to fire form them into ARC brass? I cant find a print on a 5.6x39 or a 220 Russian

 

[1raggedhole]

Certainly it should be possible since the arc, ppc, and grendel all have the 220 Russian as parent case, but you are right that the devil will be in how to properly form the case. Here are 220 Russian dimensions from Ken Howells book:

 

[AndrewB]

Thanks very much for the print. Once I have the reamers in hand, I will mic them and check that versus the 220 russian brass but at this point, I am cautiously optimistic that they will chamber with no issues. Will see how they fire form

 

[gunsandgunsmithing]

Certainly it should be possible since the arc, ppc, and grendel all have the 220 Russian as parent case, but you are right that the devil will be in how to properly form the case. Here are 220 Russian dimensions from Ken Howells book:
View attachment 1263005

Yes, you can make arc brass from either but to say that the 220 is the parent of the Grendel, while distantly true..is a stretch since it is in no way being formed, as received, from a 220 or a Russian case.
Ultimately, the 220r is shorter and has a smaller bore, more taper and a much shallower shoulder angle. But, not a big deal to blow it out to an arc.

Conversely, a 6.5 Grendel case has a larger neck, same shoulder angle and case taper, but a longer datum point at the shoulder measurement. It's almost like saying a wsm is the parent of a saum. Similar yes, driving force, probably so. But same parent...not so much.

 

[1raggedhole]

Yes, you can make arc brass from either but to say that the 220 is the parent of the Grendel, while distantly true..is a stretch since it is in no way being formed, as received, from a 220 or a Russian case.
Ultimately, the 220r is shorter and has a smaller bore, more taper and a much shallower shoulder angle. But, not a big deal to blow it out to an arc.

Conversely, a 6.5 Grendel case has a larger neck, same shoulder angle and case taper, but a longer datum point at the shoulder measurement. It's almost like saying a sum is the parent of a small. Similar yes, driving force, probably so. But same parent...not so much.

All of these are coming from 7.62x39. Necked down to make the 220 russian, and necked down with other changes to make the grendel. In all cases, 6arc, 6.5 grendel, and 6ppc all come from the same parent, 7.62x39 or 220 russian, depending on what direction you’re looking. What other parent case would it be?

 

[gunsandgunsmithing]

All of these are coming from 7.62x39. Necked down to make the 220 russian, and necked down with other changes to make the grendel. In all cases, 6arc, 6.5 grendel, and 6ppc all come from the same parent, 7.62x39 or 220 russian, depending on what direction you’re looking. What other parent case would it be?

I'd say, most every cartridge is at least a cousin to one another, then.

 

[Mulligan]

I fireformed a few Lapua 220 Russian cases into 6 Grinch cases. The neck ended up a lot shorter in the Russian cases verses using a Lapua Grendel case to start with. In the end, I used the Lapua Grendel case to make the rest of my Grinch brass. I am not sure if there is any difference between a Grinch and ARC or not, just haven’t studied it?
CW

 

[gunsandgunsmithing]

I fireformed a few Lapua 220 Russian cases into 6 Grinch cases. The neck ended up a lot shorter in the Russian cases verses using a Lapua Grendel case to start with. In the end, I used the Lapua Grendel case to make the rest of my Grinch brass. I am not sure if there is any difference between a Grinch and ARC or not, just haven’t studied it?
CW

Its between a grendel and a ppc.

 

[Oso]

I fireformed a few Lapua 220 Russian cases into 6 Grinch cases. The neck ended up a lot shorter in the Russian cases verses using a Lapua Grendel case to start with. In the end, I used the Lapua Grendel case to make the rest of my Grinch brass. I am not sure if there is any difference between a Grinch and ARC or not, just haven’t studied it?
CW

Mulligan - How did you form the cases - Direct Method (load & shoot) or did you first go with a COW Method?

 

[Mulligan]

Mulligan - How did you form the cases - Direct Method (load & shoot) or did you first go with a COW Method?

Load and shoot
I tried seating long and false shoulder..... false shoulder was more uniform but the neck was way to short.
CW

 

[EOD Rob]

I resized a mess of 7.62x39 brass to the 6.5 Grendel. If I am correct, 7.62x39 has 220 Rus for a parent case. I havent taken it to the next step of 6ARC, but the Grendel brass comes out very nicely. After the first firing, you cant tell the difference.
If I was going down to 6ARC, I would do it in steps, then anneal them.
However, going from 220 to 6ARC shouldnt need to step up however, I could see the need for the fire forming and annealing.

 

[HardwoodPro]

Yes, fire form and then gtg

 

[SD guy]

I have done it with good success. I would favor a dedicated fire forming barrel. In my case I bought a Savage axis as my dedicated fire forming rifle. Search fire forming 6ppc and the options are essentially the same.
1.) Fire form with no projectile & a fast powder. seemed to be favored by the bench rest crowd. Trim after fire forming.

2.) Fire form w a 223 cal bullet & works surprisingly well. Trim after fire forming based on my experience.

3.) Fireform with a 6mm bullet of your choosing and a moderate charge of propellant. Ramshot Tac was my choice. Shoots quite accurate & can be very practical. Trim B4 fire forming.