OldVet seeking help/info on wildcat cartridge

OldVet seeking help/info on wildcat cartridge

This is a discussion on OldVet seeking help/info on wildcat cartridge within the General Firearm Discussion forums, part of the Related Topics category; 6X45mm round? Basically, it is a .223 case necked up to take a .243.6mm bullet. Anyone have any experience/first-hand knowledge with it? I have two ...

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Thread: OldVet seeking help/info on wildcat cartridge

  1. #1
    VIP Member Array OldVet's Avatar
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    Question OldVet seeking help/info on wildcat cartridge

    6X45mm round?

    Basically, it is a .223 case necked up to take a .243.6mm bullet. Anyone have any experience/first-hand knowledge with it?

    I have two .223 rifles, a Rem 788 and an AR, and long ago fell in love with the little round. However, I've never considered it more than a very effective varmint round and, frankly, have become a bit bored with it.

    I like unusual calibers, the .30 Herrett being one of my favorite. It's basically a .30-30 Short for the uninformed. I don't mind the extra work to "roll" my own ammo if that's what it takes.

    One of the advantages of the AR design is its ability to change calibers by simply swapping uppers, 5.56 to 300 BO for instance. I'm under-impressed with the 300 BO. I passed on the 6.5 Grendel because while adaptable to any AR-15 lower, it requires a different BCG and magazines as well.

    The 6x45, on the other hand, requires only a barrel change. Standard 5.56 BCGs and magazines are GTG.
    Making ammo is as simple as running .223/5.56 cases through a 6x45 resizing die and loading it like any other round. And 5.56 cases are readily available for conversion.

    The problem is, no one makes a 6x45mm upper, at least not that I can find, and where I can find a barrel, it runs $300-350. Then I'd have to build a separate upper because I don't want to break down my 5.56 upper to convert it. That means a much higher price just to shoot an unusual caliber, more than I care to spend for a rifle that will be range use only.

    An alternative is to pick up a Henry single-shot rifle (the old H&R model) in .223 and have it bored to .243. I'm not sure if that can be done or who could do it. The single shot would have several advantages, one being it could have more free bore to accept longer bullets and longer COL rounds that the AR magazine won't allow. I find the rifles running around $350 online.

    So my question is (finally), does anyone know who may be able to re-chamber and re-bore a finished .223 barrel to .243, and what it might cost to do so?
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    Still pricey but how about buying a barrel bored to .243 then have it chambered to 6X45, I have a Shaw barrel on a custom .220 Swift I built many years ago.
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    VIP Member Array OldVet's Avatar
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    Quote Originally Posted by msgt/ret View Post
    Still pricey but how about buying a barrel bored to .243 then have it chambered to 6X45, I have a Shaw barrel on a custom .220 Swift I built many years ago.
    The problem with that would be having a barrel blank adapted to the Henry receiver. Lot of work there.
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    https://www.ar15performance.com/__va..._wildcats_misc

    He speaks of 6mm a ways down the page.

    I have one of his custom barrels on my 6.8 Savage. Good stuff.
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    Almost all of the "wildcat" or not commonly used caliber uppers are very pricey. They just don't order barrels in bulk, so you're looking at quite an expense initially. My favorite conversion caliber for the AR is the 300 Blackout, which performs well enough for deer (select an appropriate deer bullet and you can load your own easily), and perhaps even buy them already loaded. Here is the best resource in the country right now:

    https://palmettostatearmory.com/ar-1...ssemblies.html

    Check out their 6.5 Grendel uppers. They are very reasonably priced - $320 for a complete upper with bolt carrier group and charging handle. The Grendel is designed for long range shooting and might be a bit better for that purpose.

    The other great round for the AR is the 6.8 SPC (.277 caliber). My 6.8 performs well all the way out to 800 yards and would probably go further with the right load. Unfortunately Palmetto doesn't make a 6.8 upper. I wrote them a few times and encouraged them to do so.
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    I've considered the Grendel, and it is not beyond rejection, but I'm hoping for a .223-based cartridge.
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    6mm AR Home Page
    AR-15 Upper Recievers
    6mmAR -- 6mm Solution for AR-15s (Grendel Brass)


    I was bored with .223 and went to an AR-15 in .50 Beowulf so the AR-15 magazine becomes a single stack.

    .50 Beowulf® - alexanderarms.com
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    VIP Member Array OldChap's Avatar
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    I was initially underwhelmed with the 300 also - until I really started taking a look at what it is capable of doing. It is THE premier home defense round - ask the U.S. Navy SEALs. It can easily outperform a 16 inch barrel 5.56 in a 8.5 inch barrel. Here is a lot of excellent information:

    300BlkTalk - Index page

    The only negative I've been able to discover about the 300 is being absolutely sure you don't mix up ammo between it and a 5.56. I use these to stop confusion:

    https://www.amazon.com/Sighthound-Ba...und+Ballistics
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    Might check with @ThirdShift . I believe he could give ya some information on that.
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    @OldVet Did I read right? Are you looking for a varmint cartridge? If so I would look for this one - supersonic at 1,000 yards!

    https://palmettostatearmory.com/psa-...th-bcg-ch.html

    $300 for the upper WITH bolt carrier group and charging handle. I'll see what mags it takes, just in case you're interested.

    Here ya go - it is made from a necked down 6.8 SPC and is a real hotrod round. I uses 6.8 magazines, which are pretty inexpensive nowadays, and PSA sells it with the 6.8 bolt carrier.

    1450 ft lbs at the muzzle with a 90 grain Sierra HPBT Match King and it is still running above 1150 fps at 1,000 yards. Here is a kind of sales oriented page, but in all honesty, this new round is going to be very popular. Federal designed it, so there is available factory ammo. And that 90 gr HPBT MK would be fine on southern deer.

    Just something else to muddy the water. Sorry.
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    Quote Originally Posted by sammeow View Post
    Might check with @ThirdShift . I believe he could give ya some information on that.
    Thanks, Sam.

    @OldVet . Bob Bailey here can certainly do that. He's a wizard. His phone number is (479) 264-7630 or email him at [email protected]. I forget his handle on these forums but his avatar is the one with the Star Wars stormtrooper holding an AR pointed at the camera.
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    VIP Member Array OldVet's Avatar
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    My intent for this new caliber is just something to play with at the range. Something new to tinker with and see what it can do, mostly at a 100-yard open range. It's meant neither for hunting (but could) nor home defense (got better stuff).

    The AR part came in because of the ease of swapping upper receivers, but I really prefer a .223-based round that would utilize common .223 CBGs and mags. The 6x45mm case is almost too easy to make.

    The Henry rifle came to mind because it really needs to be only a single shot for my purposes. Re-bore the barrel and done for the most part. I haven't played machinist since high school, although I did impress an A&P instructor when I machined an AN bolt into an elevator hinge pin. But as far as barrel work goes, pretty much clueless on this end.

    I even thought about rebarreling my 788 to 6x45, but I really hate to ness with that rifle.
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    I know a .357 works well on wildcats, including cougars. Marlin .357 rifle. Mine is more rare, as got it with a 24" barrel..... most people didn't know they ever made them, but they did. You just had to call the company direct to order it. For long distances, would need what you are talking about. I think a 5.56 or 270 works. When I'm in the mountain wooded areas , I take a 30-30 lever action, more in case of a black bear... and will eliminate a cougar as well.
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    Just bite the bullet on a custom match grade 6x45 AR barrel, it's your cheapest and easiest option.

    Personally I went with the 300 blackout for a PDW and 6.5 Grendel for punching paper.......... and it took me a long time to decide to expand my ammo cache calibers.
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    Prices of everything, especially "custom" products, have doubled a time or two in the last couple of decades. Selection and availability are probably better than ever, but I routinely suffer from sticker shock when perusing the marketplace.

    About 30 years ago Interarms had the nice little Mark 10 "mini-mauser" rifles, barreled actions, and actions were available at very reasonable prices. I purchased the action and had a Douglas 6mm barrel blank chambered to 6X45mm and turned down to "pencil barrel" dimensions (as light as possible) and 21" length. Installed the new barreled action in a walnut stock of classic sporter style. Mounted a Bushnell 1.75-4.5 variable scope. Ended up "all in" at under $500 for a handy little carbine 39" overall and weighing in at just 6 lbs.

    As the OP points out, ammo is as simple as running .223 brass through a 6X45 die with neck expander for 6mm bullets. Nothing could be easier. Of course, for use in the AR gas-operated semi-auto you would have less flexibility than I had with the bolt action rifle, but it shouldn't be too difficult to work up a load that functions properly.

    Loaded with 90 grain Speer bullets it chrono'd at 2800FPS (about 200FPS behind the .243 Winchester). Groups from the bench regularly under 2" at 100 yards. Plenty adequate for antelope or mule deer here in Colorado. Very light weight for field carry. Recoil was negligible.

    Had so much fun with that project I ordered the standard Mark 10 short action, barreled it with a .338 bore chambered for the .308 Winchester necked up to .338. I called it the 8.5X51mm (Federal later came along with the same thing as the .338 American or some such moniker, and I ground my teeth a little bit). 22" pencil barrel with 2-leaf express sights regulated for 100 and 200 yards. Another great lightweight hunting rifle suitable for just about any North American hunting. I especially liked a hard cast 200 grain RN-GC bullet at about 2100FPS. Probably would have been just as well off with a .358 Winchester (standard cartridge) but I was really getting into "doing my own thing" at the time.

    Both rifles disappeared in a burglary of my home, never recovered. I doubt that anyone who ended up with them ever got much use out of them, as relatively few of us are into "rolling our own" ammo (especially wildcat cartridges). Probably couldn't do either of those again for less than double the price of a good factory-made rifle.

    Oh well. Might as well have some fun in the time left to do so.
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