Help identify Wildcat 6mm - 300 HH Mag

[Mosin Mounts]

I'm looking to correctly identify some wildcat ammo I have. I picked up a bunch of stuff at an estate sale and among the goodies were 60 wildcat rounds.

The cases began life as 300 H&H Magnum and have been beautifully necked down to 6mm (.243).

Length to shoulder: 1.725
Length to neck: 1.850
Overall case length: 2.190
Total cartridge length: 2.860
(All measurements are approximate)

I've looked all over the internet and can't find this exact wildcat. If anyone has it in a book, I'd sure like to know more about it.

 

[fireball168]

6mm-6.5 Remington Magnum, your measurements are almost exact.

Otherwise, it is rather close to .244 Durham Magnum:
2.25 case length
Base to shoulder 1.836"
Base to neck 1.914"

 

[Mosin Mounts]

I checked the 6.5mm Rem. Mag. specs and it's very close indeed, but the projectile dia. on my rounds are definitely .243 (6mm), not .264 (6.5mm).

Also tried to find any specs on a 6mm Magnum, but couldn't find any good pages with dimensions.

 

[Fullmag]

I have one round like what your describing and know nothing about it. Does yours have a lead bullet or jacketed bullet?

 

[Mosin Mounts]

Mine has a jacketed soft point projectile.

I just searched through a few more charts and found that my rounds measure almost identical to the 7mm Winchester Short Magnum, only they're 6mm and the neck length is .090 shorter.

 

[buford t justice]

I have looked through my books and the net and although I can find at least three cartidges that appear to be necked and shortened 6mm belted magnums ,I can't seem to find case dimensions.
they are

6mm atlas
6mm incinerator
6mm mach IV

good luck with your search!

 

[tenring]

Wildcat Cartridges

 

[kludge]

I checked the 6.5mm Rem. Mag. specs and it's very close indeed, but the projectile dia. on my rounds are definitely .243 (6mm), not .264 (6.5mm).

Hence the reason he said "6mm-6.5 Rem Mag" and not "6.5 Rem Mag".

The 6mm-6.5 Rem Mag is a necked down 6.5 Rem Mag, but 6.5 RM brass is hard to find/expensive so people form it from most any belted magnum case.

 

[Mosin Mounts]

I know people make hard-to-find brass out of any readily available parent brass they can find (I've done it myself with 8x56 and 8x60), but I hadn't thought about basing a wildcat round on a hard-to-find parent cartridge. That adds a layer of complexity, depth, maybe even style..? Very intriguing!

As I mentioned, it's nearly identical to the 7mm WSM, to the thousandth of an inch, except for the projectile diameter and neck trim length. Not close, identical. But I think you guys have something here. The case dimensions aren't close enough to 6.5 Rem Mag to be a 6mm-6.5 Rem Mag, but it could very well be a 6mm-7mm WSM.

I wasn't aware that it was common for wildcatters simply resize the neck, leaving the remainder of the cartridge untouched. Sounds too simple. I always thought there would need to be some shoulder work involved. Nor did realize that the naming procedure for such a cartridge was to simply toss the new diameter (6mm) in front of the parent cartridge (7mm WSR) with a "-" between the two.

I'm very intrigued, enough so that I'll start looking for old wildcat books at the gunshows. Even if I don't start wildcatting myself, I'm sure I'll get some wholesome entertainment and likely learn something in the process.

Meanwhile, I think I'll use some 348 brass to form some 8mm Kropatschek cases, then resize the necks to .308 to make a 7.62-8x60K. I'll leave the rounds laying around for someone to stumble across in 30 years. To throw them off even more, I'll load them 70% full of Trail Boss and crown them with lead wad cutters and paint the tips hot-pink.

 

[Broom_jm]

OK, now I'm really confused...

In your first post, you said they started life as 300H&H cases (belted), but now you're saying they are "identical" to 7mm WSM, "to the thousandth of an inch".

Those two cases are radically different. The WSM line is not belted and has a substantially larger body diameter, with a rebated rim. I'm sure what you have is a 7WSM, necked down to shoot 6mm bullets, but if that's true, they would bear no resemblance to a 300H&H or a 6.5Rem Mag, necked down.

 

[kludge]

I know people make hard-to-find brass out of any readily available parent brass they can find (I've done it myself with 8x56 and 8x60), but I hadn't thought about basing a wildcat round on a hard-to-find parent cartridge.

Belted magnum brass is not hard to find at all. You can use almost any of them - except the really big ones (African cartridges >40 caliber) and the .450 Marlin

 

[Mosin Mounts]

To Broom_jm:

Thanks for bringing up the belt and case diameter differences. My only resources for case dimensions are the often grainy images I manage to google by the light of my iPhone. In my haste I only measured the linear dimensions of my cartridge and didn't compare any diameters other than the rim, and I'm not used to dealing with belted cartridges like the 300H&H, so I overlooked that the 7mm WSM wasn't belted. My apologies for the confusion. The case I have is definitely belted and has 300 H&H MAG stamped on the rim.

That means it's not a 6mm-7mm WSM after all, and still definitely not a 6mm-6.5 Rem Mag.

 

[Mosin Mounts]

Belted magnum brass is not hard to find at all. You can use almost any of them...

...but 6.5 RM brass is hard to find/expensive so people form it from most any belted magnum case.

It was suggested that my mystery cartridge might be a 6mm-6.5 RM in which case the 6.5 RM would be the "hard-to-find' parent case, hence the use of a 300 H&H "not hard-to-find" case.

 

[kludge]

If you're looking for case dimensions, this might help.

page8d

 

[Broom_jm]

To Broom_jm:

Thanks for bringing up the belt and case diameter differences. My only resources for case dimensions are the often grainy images I manage to google by the light of my iPhone. In my haste I only measured the linear dimensions of my cartridge and didn't compare any diameters other than the rim, and I'm not used to dealing with belted cartridges like the 300H&H, so I overlooked that the 7mm WSM wasn't belted. My apologies for the confusion. The case I have is definitely belted and has 300 H&H MAG stamped on the rim.

That means it's not a 6mm-7mm WSM after all, and still definitely not a 6mm-6.5 Rem Mag.

No need to apologize, but the devil really IS in the details, when it comes to cartridge dimensions. Rimmed, rimless, semi-rimmed, rebated, belted, bottle-necked, radiused, length, diameter, shoulder angle...etc, etc.

What you have may well be a 6X6.5RM. You cannot determine from the headstamp whether or not that is true. If it has all of the external dimensions of the 6.5 RM case, save for a 6mm case mouth, it may be.

A more common variant would be a 6mmX264 Win Mag, formed from 300 H&H brass. Without a complete laundry list of dimensions, it's difficult to tell. Is there a set of reloading dies available? That might shed some light.