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Old December 5, 2020, 05:44 AM   #1
fan_of_flux
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6x45 wildcat

I was watching a youTube video on the 6x45 wildcat with a AR15 platform. Has anyone else tried this cartridge? It looks very interesting, and having a small sized .243/6mm cartridge in a .223/.556 necked up case may make for a very nice longer range performance platform.
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Old December 5, 2020, 06:37 AM   #2
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You might find it's not that great for long range because you can't load the longer, higher BC bullets and keep them short enough to fit the magazine in an AR. The limit is about 70-75 grain bullets.

If you're serious about a 6mm in the AR with the 5.56 case take a look at the 6mm Mongoose, it's a shorter case with the TCU taper and works well with bullets up to 90-100 grains at magazine length, has about 1 grain more case capacity and a little more velocity than the 6x45. The longer match bullets like 95 SMK still don't work at mag length.

Another option is the 6mm ARC, but I don't like how much was taken out of the bolt to make it work in an AR.
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Old December 5, 2020, 08:59 AM   #3
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It's mostly a one-trick pony--but the sharp's 25-45 driving a 87 gr hot cor is quite the thing in a 5.56 case.
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Old December 5, 2020, 09:45 AM   #4
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It's a kickass option. Simple neck-up operation, you get 100fps more with 10gr heavier bullet and lower pressures. Longer reach, more swat when it gets there and a TON of bullet choices. AR-15's should have originally come in 6x45mm. Mine makes mince out of bunnies to 400m.
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Old December 5, 2020, 02:30 PM   #5
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Whenever you take a liking to anything that is remotely new or unusual, look for ammo and/or brass first. Graf's shows 6 x 45(AKA 6mm-223 brass made by Quality Cartridge as 'Out of stock'. Runs $36.99 per 20 when there's no pandemic interfering with our play time. Midway doesn't list any.
Means you'll have to neck up .223 brass assuming to have any. And assuming you can find an upper.
Hodgdon has data for 60 to 100 grain bullets. 90 grain bullets(Only because I use 'em in .243) run from a bit over 2500 FPS to a bit over 2700 FPS. A 90 grain .223 runs from a bit over 2400 FPS to from a bit over 2500 FPS as a comparison. Out of a 1 in 9, 24" barrel.
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Old December 5, 2020, 03:45 PM   #6
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6x45mm belongs in a bolt gun.

I built a 6x45mm AR about 6 years ago.
Even when using magazines (I forget which brand) that allow a 2.280" COAL, bullet selection is still extremely limited. They just won't fit in the magazine, without being seated so deeply that the ogive is well inside the case mouth.

At this point, I run a few varmint bullets (48 to 60-odd grains) just fine, but still have occasional feeding issues with 85/87 gr bullets, and 90 gr Partitions. ...Because the ogive is below the case mouth and the mouth snags once in a while.
I have not found a bullet heavier than 90 gr that can be used reliably.

You may note that that means I also can't crimp those bullets. So setback is a possibility.

I still like the cartridge and the varmint loads make for a fun blaster. But, when limited to the dimensions of an AR, it is not the cartridge that I thought I was getting into.
Rather than being a multi-purpose rifle (varmint/target/'light' big game), I ended up with a 'walking varminter'.


But give me a bolt gun in 6x45mm, with the ability to load to a COAL of up to 2.8", and I'll be happier than a pig in ....
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Old December 5, 2020, 05:06 PM   #7
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Quote:
6x45mm belongs in a bolt gun.
Hard to argue with that.

6mm, 6.5mm, 7mm wildcats on the 223 case have been around for a long time. Back in the 1980s, the 7mm TCU and 7mm Ingram (7X45) were the sweethearts of the silhouette shooting world. 6mm/223 or 6X45mm was all the rage for varmint shooters in the 1980s and 1990s. But mostly in bolt rifles. All of the ARs I have seen rechambered for a 223/5.56 wildcat end up going back to 223/5.56 sooner or later due to lackluster performance because you have to push the bullet back into the case to get them to fit an AR magazine. Yes, 6mm bullets can buck the wind a little better, but they leave the barrel going too slow so they have too much drop at range. I have a customer that has tried just about every iteration of wildcats in ARs. Always ends up going back to 223/5.56.

Back in the 1980s, I sold a Howa 1500 in 223 to a customer who was a big-time silhouette shooter. He had it rebarreled to 7mm TCU, his favorite cartridge for silhouette shooting. Launched a 162 gr bullet at around 2,200 fps from a 20" barrel, about like a 30-30. He loved it. I just shook my head.
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Old December 5, 2020, 07:06 PM   #8
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i have a 6-47 in a rem 40xb(222 rem mag case necked up to 6mm) i like it.
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Old December 5, 2020, 08:38 PM   #9
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So, what I am hearing in the comments so far is: stay with what has been a proven winner (i.e., 556, 6 arc ,and 6.5 Grendel). I really appreciate the voices of experience with this topic...kudos!
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Old December 6, 2020, 01:12 PM   #10
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Actually, I'd go with the 6x45 if an AR platform is at hand. 5.56 sucks up side it.
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Old December 6, 2020, 02:30 PM   #11
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Quote:
So, what I am hearing in the comments so far is: stay with what has been a proven winner (i.e., 556, 6 arc ,and 6.5 Grendel). I really appreciate the voices of experience with this topic...kudos
Meh.
I'm not much of a fan of .223/5.56. I still think you can have plenty of fun with an AR that is *not* chambered in .223/5.56. I just don't think 6x45mm is the right answer.

If you are okay with a very limited bullet selection, .25-45 Sharps is a good one.
.17 Remington and .204 Ruger are fun.
You did mention "long range" though. If you want to launch high BC bullets, you might consider running a long COAL with a throated .222 Remington chamber -- or a short neck without the need to throat.
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Old December 7, 2020, 12:34 PM   #12
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Is the 6X45 better than a .225/5.56 AR-15 for general use, varmint shooting, or target shooting? IMO not at all. Here is why, bullet selection and economy! There are far and away a lot more bullet selection for the .224 caliber suitable for the AR-15. Economy it's simply cheaper to reload or buy ammunition for. 6mm bullets are more expensive by a few pennies, and ammunition requires custom makers to get if you don't load your own.

Where the 6X45 or any larger caliber X45 wildcat shines above the 5.56/.223 is hunting situations for white tail deer and such. At ranges inside of 200 yards, they'll usually hit a little harder and leave better blood trails. If you're not going to go hunting with the cartridge, stick with the .223/5.56.



Quote:
i have a 6-47 in a rem 40xb(222 rem mag case necked up to 6mm) i like it
I have one as well, but it doesn't like heavy bullets. However, that's my fault I used a 1:12 twist because I got a deal on a barrel. It's a tack driver however with 55-70 grain bullets, and usually 200 fps faster than the same weight .223 at the muzzle.

I also have a 6X45 on a bolt gun with a 1:7 twist barrel so I can launch the long range stuff. You're still limited on COAL if you want to seat your bullets past mag length as to not eat up powder capacity, it also requires a custom throat. I'm finding 85 grain Sierra HPBT GK and 100 grain SPBT GK are what the cartridge is liking the best. 105 grain Nosler RDF and Berger VLD aren't shooting nearly as well.

The only reason I built the 6X45 and 6X47 was to be legal to hunt in Colorado, .243 is the smallest legal caliber in CO. That is also why I chose a bolt gun over an AR style rifle, I like to carry a bolt gun hunting. The reason I built a 6X45 over rebarreling my 6X47 to a faster twist, brass availability. That said if I rebarrel my 6X47 I'll proably go 6X204 to get an extra grain or two of powder capacity and it'll more than likely be a single shot only rifle.

Quote:
Originally Posted by stagpanther
It's mostly a one-trick pony--but the sharp's 25-45 driving a 87 gr hot cor is quite the thing in a 5.56 case.
What's its one trick? I have a buddy who shoots this cartridge in a 20" AR. He loves it as well.
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Old December 7, 2020, 07:59 PM   #13
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My whole purpose is to use my AR platform with a better BC for shots beyond 500m for Wile E, and limit the cost of change over (a barrel only); hence, the attraction to 6x45. I can load my own, and planned to do so, so ammo will not be a problem as long as I can get some a good die set from Redding.

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Old December 8, 2020, 11:29 AM   #14
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Quote:
My whole purpose is to use my AR platform with a better BC for shots beyond 500m for Wile E, ........ hence, the attraction to 6x45. I can load my own, and planed to do so, so ammo will not be a problem ......
Theory is probably going to be better than practice I fear. You are going to run out of COAL quickly due to magazine restrictions. .224 caliber match bullets designed for service rifle competitions will have higher BC numbers than a lot of 90-100 grain 6mm bullets. This means you'll have bulltes that drift less in .224 in most cases.

You really need to load up a few dummy rounds with 6mm bullets and compare to dummy rounds with .224 bullets. Load them to mag length of your AR mags and see if they'll work. It'll also give you an idea of powder capacity.

So take this from a guy who has a 6X45 in a Savage 10 bolt action. In my rifle magazine i can load a COAL of 2.39-2.42" depending on bullet used. This is a huge difference to the 2.26-2.28" restrictions an AR magazine has. I couldn't seat any 105 grain VLD style bullet in a case at 2.28" and not have the bullet ogive inside the case mouth. I also toyed with the idea of an AR-15 in 6X45, and that's why I settled on a bolt gun in this cartridge.

Black Hills has 77 grain TMK (BC .490) ammo that is for AR-15 rifles, and claims a MV of 2700 FPS from 20" barrels. A 6X45 running a Hornady 105 grain BTHP (BC .530) match bullet at 2500 fps which is about a best guess from a 20" barrel. The TMK bullet will drift 25.5" in a FV wind and the BTHP will drift 22.9" in the same wind. So if you believe a 2.6" advantage at 500 yards is what you need to kill coyotes then by all means build the 6X45. IMO you're getting the same result with about 175 lb-ft more energy at the 500 yd coyote range you discuss, so you're essentially shooting the same cartridge.
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Last edited by taylorce1; December 8, 2020 at 03:33 PM.
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Old December 8, 2020, 03:00 PM   #15
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I pretty much decided against the 6x45 in an AR platform. However, I am almost married to the idea of a 6mm ARC. A little most upfront cost, but videos I have watch so far are demonstrating some real nice down-range performance.
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Old March 1, 2021, 12:52 PM   #16
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I've just recently started shooting the 6x223 from my contender but it looks promising
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