Can you convert .223 brass into 7.62x39 brass?

[mavracer]

Right...so I take it you didn't actually take a fired case, cut, and resize it to see what you end up with? And of course, we haven't even brought fireforming into it yet. Anywhooo, you still don't seem willing to put 5K down on your statement that it is impossible. My position stands...I can cut down a 5.56 or .223 case, size it to 7.62x39, replace the bolt face in a 7.62x39 AR with a 5.56 or .223 bolt face, and make it run. I also think I could ***probably*** mod the 7.62x39 bolt face enough to make it run, but it would never run real 7.62x39 again. You gotta pay to see it though. Gonna be my Huckleberry?

As long as your 5k is on the table too you're on.

 

[EricBu]

As long as your 5k is on the table too you're on.

Absolutely! But you got put your's up front, since I'm buying your plane ticket.

If you really want to challenge me, tell me I can't make it run in an AK (would actually be easier I think...because...AK).

And when we're all done, I'll even grill up steaks and buy the beer (with the 5K I won from you of course).

 

[EricBu]

Moot point. This is what the OP is really asking:


It looks to me like what he really wants to do is make 300BLK out of 7.62x39mm. Since the body of the 7.62mm is larger than the body of the 5.56mm, it can potentially work but, he'd have to cut the case head down to use the same bolt head as for 5.56mm->300BLK. That's possible, too but, not recommended (waste of time and effort). Add to that, it means placing a whole lot of stress on the 7.62mm squeezing them down (base/rim diameter 0.447") to fit the 300BLK (base diameter 0.376"/rim diameter 0.378"). Again, can it be done? Sure, probably. A lathe and some sizing lube and you're off to the races. But, as you can see from the image (snatched it off Wikipedia) why would you?
View attachment 1063552

You got that from OP? Really, I understood it as he was already making 300 BLK from .223 and wanted to know if he could modify the jig and use the same process to make 7.62x39 from .223. Which we know the answer is "No, not really...but yes with effort and gun modifications". Which is why my original post recommended buying some new Starline 7.62x39 instead of dealing with the hassle.

 

[mavracer]

Absolutely! But you got put your's up front, since I'm buying your plane ticket.

If you really want to challenge me, tell me I can't make it run in an AK (would actually be easier I think...because...AK).

And when we're all done, I'll even grill up steaks and buy the beer (with the 5K I won from you of course).

Let me try one more time to have you save face (in more ways than one)

This is what happens when you fire form a 223 round in a 7.62x39 chamber cutting 6mm off and sizing the neck to hold a 7.62 bullet won't change the case diameter where these cases split. The only thing you'll accomplish is creating more gas in your face (and possibly brass) actually building pressure pushing a 30 cal bullet down a 30 cal bore.
Feel free to pee on the electric fence yourself, I don't need 5 grand that bad.

 

[GeoDudeFlorida]

You got that from OP? Really, I understood it as he was already making 300 BLK from .223 and wanted to know if he could modify the jig and use the same process to make 7.62x39 from .223. Which we know the answer is "No, not really...but yes with effort and gun modifications". Which is why my original post recommended buying some new Starline 7.62x39 instead of dealing with the hassle.

That was what I got. Could be wrong. Maybe the OP can clarify if he's still around. Could have been a drive-by posting. Never know.
With a good lathe and short mill there's just not much can't be done. Question is, is it really worth the setup time and materials?
As for blowing out a 5.56mm to fit a 7.62mm sizing die and run blown-out brass with a small head in an AR platform, sure. You could even solder brass or tinker's silver to the rim to make it "real" 7.62x39mm if you were of a mind to. Question again is, why? Only the user can answer that.

 

[mavracer]

With a good lathe and short mill there's just not much can't be done.

I've yet to figure out how to make something a larger OD with a lathe. I've cut it three times and it's still too small lol.

 

[EricBu]

Let me try one more time to have you save face (in more ways than one)
View attachment 1063557View attachment 1063558
This is what happens when you fire form a 223 round in a 7.62x39 chamber cutting 6mm off and sizing the neck to hold a 7.62 bullet won't change the case diameter where these cases split. The only thing you'll accomplish is creating more gas in your face (and possibly brass) actually building pressure pushing a 30 cal bullet down a 30 cal bore.
Feel free to pee on the electric fence yourself, I don't need 5 grand that bad.

That's certainly what happened when you did it. <shrug> I don't need 5K that bad either, but it sure would have been fun.

 

[GeoDudeFlorida]

I've yet to figure out how to make something a larger OD with a lathe. I've cut it three times and it's still too small lol.

You use the lathe to make a series of progressively larger expander balls. Not that hard. Anneal between expansions if you get nervous about cracks or uneven expansion. Expand until you have a correct diameter straight-wall case, to be sure. That's the long way but for sure you'll end up with all of your max dimensions in spec'. Then reform it to the bottle-necked profile. Again, you can go slow and reform it one small step at a time or take chances and do it in one or two steps. It's brass. It's forgiving.

 

[EricBu]

That was what I got. Could be wrong. Maybe the OP can clarify if he's still around. Could have been a drive-by posting. Never know.
With a good lathe and short mill there's just not much can't be done. Question is, is it really worth the setup time and materials?
As for blowing out a 5.56mm to fit a 7.62mm sizing die and run blown-out brass with a small head in an AR platform, sure. You could even solder brass or tinker's silver to the rim to make it "real" 7.62x39mm if you were of a mind to. Question again is, why? Only the user can answer that.

Lol, exactly. People have done some crazy things over the years, especially trying shoot old rounds that have gone by the way side. Worth it, not worth...only to the guy trying things. For me, I'd buy the brass if I couldn't find any once fired and be done with it. Hell, I'm the guy who reloaded steel cases during the obama ammo shortage. Worked fine, twice...and you had to use fingernail polish across the primers to keep them from falling out.

 

[EricBu]

You use the lathe to make a series of progressively larger expander balls. Not that hard. Anneal between expansions if you get nervous about cracks or uneven expansion. Expand until you have a correct diameter straight-wall case, to be sure. That's the long way but for sure you'll end up with all of your max dimensions in spec'. Then reform it to the bottle-necked profile. Again, you can go slow and reform it one small step at a time or take chances and do it in one or two steps. It's brass. It's forgiving.

Just goes to show you how a machinist thinks! Interesting, and for sure workable. I'd have probably annealed entire body, just cut it down, dropped in a grain of TG, filled it with oatmeal to just below the kneck, and dropped a dollop of epoxy on top. Fire it and measure, rinse lather repeat annealing between each firing. Brass is forgiving;-) Hahaha

 

[GeoDudeFlorida]

Lol, exactly. People have done some crazy things over the years, especially trying shoot old rounds that have gone by the way side. Worth it, not worth...only to the guy trying things. For me, I'd buy the brass if I couldn't find any once fired and be done with it. Hell, I'm the guy who reloaded steel cases during the obama ammo shortage. Worked fine, twice...and you had to use fingernail polish across the primers to keep them from falling out.

Yup. I've made .25-303 brass from .303 Mk. VII and its a huge pain for a cartridge that's basically a .257Roberts but I was given a barrel by a Tazman so I had to use it. I also made a .35-303 for a Cadet frame using a worn out .35Rem barrel and a .303 reaming tool. It worked remarkably well - kind of between a .358Win and .35Whelen - but making brass was a huge PITA. But it were fun and I sold it for about $300 more than I had into it. I kept the .25-303 barrel and sold the the No.1 with its original barrel put back for chump change. Should've kept it.

 

[GeoDudeFlorida]

Just goes to show you how a machinist thinks! Interesting, and for sure workable. I'd have probably annealed entire body, just cut it down, dropped in a grain of TG, filled it with oatmeal to just below the kneck, and dropped a dollop of epoxy on top. Fire it and measure, rinse lather repeat annealing between each firing. Brass is forgiving;-) Hahaha

Nah. That's too much work. Once you have the tooling, making the next one takes almost no time. Make as many as you want until the tooling wears out. Using powder and oatmeal is the hard way. Waste of good primers.

 

[Carl N. Brown]

                   5.56x45mm/.223 Rem      7.62x39mm
Case Dimensions
Neck diameter      6.43 mm (0.253 in)      8.60 mm (0.339 in)
Shoulder diameter  9.00 mm (0.354 in)     10.07 mm (0.396 in)
Base diameter      9.58 mm (0.377 in)     11.35 mm (0.447 in)
Rim diameter       9.60 mm (0.378 in)     11.35 mm (0.447 in)
Rim thickness      1.14 mm (0.045 in)      1.50 mm (0.059 in)
Case length       44.70 mm (1.760 in)     38.70 mm (1.524 in)
Case capacity H20  1.85 cm3 (28.5 gr)      2.31 cm3 (35.6 gr)
Bullet, cartridge:
Bullet diameter    5.70 mm (0.224 in)      7.85-7.92 mm (.309-.312")
Land diameter      5.56 mm (0.219 in)      7.62 mm (0.300 in)
Overall length    57.40 mm (2.260 in)     56.00 mm (2.205 in)

The case body of a .223 case cannot be sized up to match a 7.62.39mm.
The 5.56/.223 shoulder diameter, base diameter, rim diameter, rim thickness will not grow in a sizing die for 7.62x39.

 

[mavracer]

You use the lathe to make a series of progressively larger expander balls. Not that hard. Anneal between expansions if you get nervous about cracks or uneven expansion. Expand until you have a correct diameter straight-wall case, to be sure. That's the long way but for case you'll end up with all of your max dimensions in spec'. Then reform it to the bottle-necked profile. Again, you can go slow and reform it one small step at a time or take chances and do it in one or two steps. It's brass. It's forgiving.

HAVE EITHER OF YOU EVER LOOK AT A CROSS SECTION VIEW OF RIFLE BRASS

The circled part is called the case head it's basically solid with a small flash hole thru it, a hole you really don't want a lot bigger.
A 5.56 case is .377 here and the 7.62x39 is .447 an expander ball isn't going to change this diameter and you're creating a situation you really want to avoid.

 

[GeoDudeFlorida]

HAVE EITHER OF YOU EVER LOOK AT A CROSS SECTION VIEW OF RIFLE BRASS
View attachment 1063563
The circled part is called the case head it's basically solid with a small flash hole thru it, a hole you really don't want a lot bigger.
A 5.56 case is .377 here and the 7.62x39 is .447 an expander ball isn't going to change this diameter and you're creating a situation you really want to avoid. View attachment 1063564

I made parts for space craft the "smartest people in the world" said would never make orbit. They made orbit. Some of them are still up there.
I'm a machinist. "Impossible" is just a word.

 

[mavracer]

I made parts for space craft the "smartest people in the world" said would never make orbit. They made orbit. Some of them are still up there.
I'm a machinist. "Impossible" is just a word.

Spent 33 years assembling aircraft had plenty of scrap tags written cause the part is machined wrong and WON'T WORK.