My gunsmith is putting ideas in my head....

Chunkymilk

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I have always thought that a 10mm MAC would be pretty cool, but creating one that would work would be rather difficult, especially trying to find a mag that could work with the platform, redesigning uppers etc. i was chatting with my gunsmith who told me about the 400 corbon cartridge. basically its a .45 casing necked down to .40/10mm, and delivers 10mm ballistics (1300+FPS with 165gr projos) with pressures closer to .45 acp than 10mm (just a touch hotter than 45, but significantly lower than 10mm)

Supposedly...... i could convert one of my M10/45 uppers to 400 corbon with nothing more than a barrel swap. My gunsmith says making a barrel from a blank would be rather simple so long as we can get our hands on a chamber reamer. As far as ammo, i roll my own, and .45acp can be easily turned into 400 corbon by simply running it through a sizing die, then using 10mm components. ammo dimensions are very similar (length and width) and should (ceteris paribus) run in my grease gun mags with zero issues.

I think it would be rather neat to try this, curious if anybody has ever tried, and what their experience was like in the offhand chance they did.
 

mattnh

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Prob need a beefier recoil spring as well
Cool idea -I wonder how fast it would run?

Might be cool to covert a Lage upper to 400 Corbin as well
 

Garrett

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I had one in a 1911 a couple decades ago. Neck is too short. It doesn’t provide enough neck tension to hold the bullet in place while chambering. About half the bullets would get pushed back in the case when chambering, running pressures up a lot. Some came out with nice rounded primers. Others came out with completey flattened primers. This was the case with both factory and reloaded ammo.

“bang, bang, POW, bang, POW, POW...”

The over pressure rounds ended up cracking the barrel locking lug. I welded it back, ensured it worked, up and sold it off along with the loading dies and a sack full of brass. I think I still have a box of factory Corbon ammo around here somewhere.

Also, you would think the bottleneck case would feed better, but the bullet tip liked to catch on the ridge in the chamber.

Personally, I’d go with the 10mm if you want more power than the .45 ACP. I have .40 and 10mm conversions for the Uzi. They feed fine from Grease Gun mags if you tweak the feed lips in slightly. I keep separate mags marked for .45 vs. 10/.40.

The IMI .45 or .41AE mags do not work with .40/10mm unless you download to 12-14 rounds.

I also have a .357 Sig conversion for the Uzi. It also doesn’t feed worth a darn. Maybe it’s that bottleneck case thing again.
 

Chunkymilk

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Prob need a beefier recoil spring as well
Cool idea -I wonder how fast it would run?

Might be cool to covert a Lage upper to 400 Corbin as well

Planning on converting my gen 1 lage upper (i have a Mk2 as well) since its got the heavier bolt in it, should negate the need for a heavier spring, although based on my reading about the pressures, dont think it should be necessary.
 

Chunkymilk

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I had one in a 1911 a couple decades ago. Neck is too short. It doesn’t provide enough neck tension to hold the bullet in place while chambering. About half the bullets would get pushed back in the case when chambering, running pressures up a lot. Some came out with nice rounded primers. Others came out with completey flattened primers. This was the case with both factory and reloaded ammo.

“bang, bang, POW, bang, POW, POW...”

The over pressure rounds ended up cracking the barrel locking lug. I welded it back, ensured it worked, up and sold it off along with the loading dies and a sack full of brass. I think I still have a box of factory Corbon ammo around here somewhere.

Also, you would think the bottleneck case would feed better, but the bullet tip liked to catch on the ridge in the chamber.

Personally, I’d go with the 10mm if you want more power than the .45 ACP. I have .40 and 10mm conversions for the Uzi. They feed fine from Grease Gun mags if you tweak the feed lips in slightly. I keep separate mags marked for .45 vs. 10/.40.

The IMI .45 or .41AE mags do not work with .40/10mm unless you download to 12-14 rounds.

I also have a .357 Sig conversion for the Uzi. It also doesn’t feed worth a darn. Maybe it’s that bottleneck case thing again.

I really appreciate the feedback! interesting experience with the neck tension, i had similar problems with other cartridges before, and discovered a cure entirely by accident. i got into casting/coating bullets a few years ago, and i use the Hi-tec supercoat. between the combination of the added .001 from the casting, the coating seems to create more friction for the casing to hold the projectile. the coated bullets have been a game changer for me, i have been treating them like FMJs and had zero issues with them. 3k rounds through my MAC, no lead fouling, just as accurate as an FMJ at a fraction of the cost.

I talked to my gunsmith over the weekend again about the bottleneck case design, based on your experiences, he didnt seem too concerned about it since he has a couple ideas for tweaks if it has issues.
 

Slowmo

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If you just want more power, trying to get it to run .45 Super would seem like the easiest path. Maybe you could get a bolt milled for some tungsten inserts and a stronger recoil spring.
 

Chunkymilk

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If you just want more power, trying to get it to run .45 Super would seem like the easiest path. Maybe you could get a bolt milled for some tungsten inserts and a stronger recoil spring.
hmmmmm...... kinda interesting... a 230gr projo at 1100 fps would be an absolute wrecking ball.... i mean i have to put a 40lb rock on the base of my steel target as it is shooting 45acp, 4 rounds hitting the target in full auto knocks it right over without the rock on it. Only issue i see here is getting brass on the regular..... atleast with 400 corbon it can be made easily from .45acp brass which i have 5 gallon buckets of. Gave me something to think about for sure.
 

Slowmo

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.45 super brass is available, it’s just not cheap. Starline sells it, maybe others too. Supposedly you can make .45 super brass (or something close to it) from lots of different rifle brass (.308 case family, .30-06 case family, 8mm Mauser, etc.), but I’ve always read it is a big pain in the rear. You have to ream the cases because the brass is too thick to seat a bullet when cut that short.
 

SecondAmend

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I had one in a 1911 a couple decades ago. Neck is too short. It doesn’t provide enough neck tension to hold the bullet in place while chambering. About half the bullets would get pushed back in the case when chambering, running pressures up a lot. Some came out with nice rounded primers. Others came out with completey flattened primers. This was the case with both factory and reloaded ammo.

“bang, bang, POW, bang, POW, POW...”

The over pressure rounds ended up cracking the barrel locking lug. I welded it back, ensured it worked, up and sold it off along with the loading dies and a sack full of brass. I think I still have a box of factory Corbon ammo around here somewhere.

Also, you would think the bottleneck case would feed better, but the bullet tip liked to catch on the ridge in the chamber.

Personally, I’d go with the 10mm if you want more power than the .45 ACP. I have .40 and 10mm conversions for the Uzi. They feed fine from Grease Gun mags if you tweak the feed lips in slightly. I keep separate mags marked for .45 vs. 10/.40.

The IMI .45 or .41AE mags do not work with .40/10mm unless you download to 12-14 rounds.

I also have a .357 Sig conversion for the Uzi. It also doesn’t feed worth a darn. Maybe it’s that bottleneck case thing again.
I don't think that any of those late night tv ad massagers are going to fix that neck tension.

I used to work with a guy who had a .30 Luger barrel made for his semi auto Uzi, and I don't think it worked well either. He was going to try 5.7x28, but I'm not sure if he ever did. He was trying to get a coyote load, not a high ballistics load.
 

Slowmo

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I don't think that any of those late night tv ad massagers are going to fix that neck tension.

I used to work with a guy who had a .30 Luger barrel made for his semi auto Uzi, and I don't think it worked well either. He was going to try 5.7x28, but I'm not sure if he ever did. He was trying to get a coyote load, not a high ballistics load.
I doubt it would work with the relatively cavernous .45 parent case of the .400 Corbon, but I thought I recalled reading that for 357 SIG, folks used compressed loads of Accurate #9 to support the bullet and prevent setback. Not sure if there is any powder that could fill the .400 Corbon case and stay within pressure limits though.
 

plodder

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I fooled around with 400 Corbon in my 1911s a few years ago. I made my own cases out of re-formed .45ACP brass. It all worked, but in the end I determined that the 400 Corbon would be a great cartridge for a 1911 if it were necked up to .45 ☺️

I have 400 Corbon dies and a 1911 barrel available if anyone wants to enjoy the same experiences.
 

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