AR-15 magazine for wildcat

[45flaco]

Hey guys. Newest wildcat cartridge feeds, cycles, and ejects great.
It's a shortened 308 case, necked up to .375 that is fired from an AR-15.
300 grain at 1000 fps for a spooky quiet subsonic, or a 200 grain at 2200 fps for a nice hog and whitetail load.

Problem is the mags. 223 mags don't work at all.
7,62x39 mags feed nicely, but because they're not quite wide enough to doublestack the 308 based cartridge, they bulge in the middle. This makes it a bit of an effort to insert into the gun, and ejecting a mag with rounds in it is nearly impossible.

I was wondering about a few solutions:
458 socom or 450 bushmaster mags.
The problem is, I'm not sure whether they're perfectly single stacked, or slightly staggered.
If I assume that they're trying to maximize capacity with a slightly staggered design, then they should work great.
But if they're designed to be perfectly single stacked, then the internal width is probably reduced, which won't help.

Anyone happen to know what AR mag would have the widest internal width?
Needs to be just slightly wider than the 7,62 AR mags.

Alternatively, any 7,62x39 mags that are actually built sturdy enough not to bulge in the middle?
The one I'm using currently is the "AR-stoner" brand

 

[stagpanther]

My 458 socom uses a retro-fitted single-stack follower, you're in a tough spot so I would look for a similar cartridge of the same case width. Then you have to worry about how well it will feed--been down this road myself and it drove me nuts. The position of the feedlips as well as the sidewall ribs of the magazine will affect how the cartridges stack under spring pressure.

 

[FrankenMauser]

.458 SOCOM magazines are standard AR mags. Some people/brands put single-stack followers in them, but they still stagger with more than one round loaded.
Pretty much the same story with .450 BM.

Try Grendel mags, if you have a friend with some that you can borrow.

 

[MarkCO]

Ditto on post #2 and #3.

Last few custom uppers I built for clients for larger case diameters, I had success with Stainless steel mag bodies. I'd machine out the ribs, tacking back in a small plate in the middle of the created slot, double wound springs and single stack .450BM followers.

 

[44 AMP]

My solution, since you are using a modified .308 Win case would be to build the gun on the AR-10 chassis. The one made for .308 Win ammo.

 

[MarkCO]

My solution, since you are using a modified .308 Win case would be to build the gun on the AR-10 chassis. The one made for .308 Win ammo.

Probably, but he appears to already have a rifle built, so that is not a viable solution to his current problem.

 

[10-96]

When the 6.8 SPC came out I recall there being issues with bulging. Know anyone with a 6.8 stainless clip you can try?

 

[45flaco]

My solution, since you are using a modified .308 Win case would be to build the gun on the AR-10 chassis. The one made for .308 Win ammo.

It's based on the 308. But cartridge length is closer to 45 acp than it is to 308. It's even shorter than 223 by a fair amount, unless I use really heavy bullets.
An AR-10 would be way larger than needed, and would have it's own problems.

 

[45flaco]

When the 6.8 SPC came out I recall there being issues with bulging. Know anyone with a 6.8 stainless clip you can try?

I'll try to find one. I think I may just end up making my own mags from scratch, all the AR mags I've seen seem to be more disposable quality metal.

 

[45flaco]

When the 6.8 SPC came out I recall there being issues with bulging. Know anyone with a 6.8 stainless clip you can try?

Ignore my last statement, you are a genius @10-96.
I searched for stainless mags, and it looks like duramag sells a stainles 7,62x39 mag that has no rear rib. I'm betting this will work without modification!
Just ordered one.

 

[45flaco]

Update! The duramag works flawlessly.
@10-96, you're awesome and probably just saved the project.

 

[MarkCO]

^Great news.