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looking for a 7mm wildcat

11K views 14 replies 7 participants last post by  nvshooter 
#1 ·
Looking for a 7mm cartridge that fits the the following criteria. 532 bolt face, fits standard long action[30/06 length],no belt. Thanks Jim:)
 
#3 ·
How hot???

Obviously, the factory is the 7mm Rem Mag. You could go short and neck up the 6.5 Remington Mag. Or, as suggested, go longer. Some '06 actions will take the full length H&H case which would allow the Weatherbys and variations there of. I have wondered about necking down the .30/338 WCF which is too close to the .308 Norma to argue about... .30/338 has a tremendous rep for accuracy... luck.
 
#5 ·
NVShooter,

Any idea what the case capacity would be on that shortened and necked down 300 RUM? You might be getting 7RM performance w/o the belt. It would sorta be like a 7WSM but a little longer?
 
#8 · (Edited)
It would sorta be like a 7WSM but a little longer?
This one is an idea for my second mildcat. I call it the 285Nevada Desert Magnum to follow-on with my 300NDM (which exists). There is a 284NDM with a .450" long neck and lower shoulder to seat those very-long-ogive Berger VLD bullets (http://www.shootersforum.com/wildcat-cartridges/23754-300rsaum-wildcat.html). But we ain't talkin' about that one, now. Back to this one. I wanted a round that was neither long-action nor short-action. A short-action is about 2.0 inches. The 308Win comes to mind. A long-action is about 2.5 inches. The .30-06 comes to mind. I wanted something right in the middle, and a magnum. I found the 7 x 57 Mauser. Just so happens Lee Precision makes a length-trimmer for it. That sealed it. From there, it's just moving the shoulder and neck locations using the ammoguide.com Cartridge Creator to get what I want. Easy. Now all we have to do is get my other one finished and get to thinkin' about thinkin' about actually doing something with the 285. Action will be a Bighorn Arms and barrel maker is up in the air. I have a barrel on order for the 300NDM with Satern for over six months. No word when it will be delivered. Nothing. Getting close to having someone else make the barrel and canceling the Satern order.
 
#6 ·
Case volume?

No, broom. No calcs yet on water volume. What I do is cut the case off at the intersection of cylindrical body and bottleneck portion. I measure that by weighing dry, then filling with water and weighing again. Then I calculate the volume of the tapered portion, allowing for the thickness of the brass. I get a volume that is prob'ly 96-98% accurate. I have found that water and gunpowder have almost exactly the same density. Can't remember now which one is heavier but they are so, so close.

I think I have a cut case laying around here, somewhere. Let me look and I'll get back to you in these pages.
 
#7 · (Edited)
Got it...

After diligent calculation I see that the case, if cut to the bottom of the neck, would hold approximately 67 grains of water. This is a plus-minus calc of about half a grain, but more to the minus side. I actually got 66.6-66.7 weighed grains of water in the case and 0.66 calculated cubic centimeters in the bottleneck. That would be approximately equal to 6-7 grains in the bottleneck, giving a useful volume of 73-74 grains. What's the estimated case volume of that belted 7mm you was talkin' about?

Looked up the 7mm Rem Mag. Found it's estimated volume is 80.8 grains of water. Assuming they are also measuring the neck, I am guessing the actual volume in the neck space is maybe 5 or 6 grains. So that makes the powder capacity about 75 grains. So, this mildcat would be very similar to the 7mm Rem Mag-- if my calculations are correct.

This mildcat idea is about 1/4-inch shorter than the 7mm Rem Mag. I like a longer neck to keep the flame inside the case, which cuts down on throat erosion. I am not one for above-celerity velocities if each shot costs a buck in barrel-replacement costs. Yeah, you're a big man (not you specifically, broom) if you say you can handle the recoil from a 180-grain, .30-caliber bullet that exits the muzzle of a 6.5-pound mountain rifle at 6700 fps, but what is it doing to the throat? I'd rather hum along at sensible velocities and shoot my rifle 1500 times than have to put a new barrel on at 800 rounds. But that's just me...
 
#10 ·
Lot would depend if you want to form brass etc also type rifle. the brass is expensive but 7mm Dakota been around for some time. Need to talk to gunsmith about the bolt face the Dakota about .010" bigger than standard mag and it be about the same or little more case capacity as necking down the 375 Ruger case.
 
#12 · (Edited)
Still another 7mm wildcat idea...

I am intrigued by the mini actions offered by some companies. I think BAT offers a true .223-sized action. The below is my idea for use in one of those. Forgot to add in the copy that the neck length is .284 inches, making this pretty much a hunting round for small game. The neck is too short to seat long-ogive bullets. Interesting to note that this round would fit into AR-15 magazines when using shorter, lower-weight bullets. I do not know if the boltface of an AR-15 can be opened to accommodate the diameter of the .30-06 head. This round is designed primarily for bolt-action rifles but knowing how wildcatters tend to think well outside the box, the possibilities are always there for a 7mm AR-15...



Should be easy to neck down to 6mm or 6.5mm for folks into those bullet diameters. Nothing done on this round yet; just an idea so far...

I think these are BAT actions. Note the mini-lefty to the upper right. I am lefthanded, so this really intrigues me...

 
#14 ·
making brass for some of the wildcats can be a real pita.
i would personaly be avoiding any cartridge requiring extensive case work.
ive been using a 7x300 weatherby for about 40 years. it just doesent get any easier than that case. simply run the 300 wby case thru a full legnth 284 die.
it does have a belt of coarse but so what? you can still headspace off the shoulder if you wish. also most would agree the brass is better than remington.
that said the 7 ultramag will outperform it by about 100 fps using same bullets.
i would also be looking hard at the 300 norma case. yes the bolt face is larger but it isnt a
problem opening a rem bolt to that dimension. the cartridge was in fact designed for rem. actions. check it out.
i have several friends owning both the 30 and 338 versions.
a 284 version would no doubt blow away my 7x300 wby.
again just neck down the 300 case and your done.

frankly we avoid using any 284 for hunting beyond about 1000yds across these wide valleys in n.c. pa.
the accuracy factor just isnt there compared to 30 cal or better yet 338 in the conditions usually encountered.
if you can afford a stable full of guns, all are nice to have.
but for those who can only afford 1 hammer, buy a big one.
 
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