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Discussion Starter · #1 ·
On Friday's updated "Forthcoming" page, RobArms mentions that 6x45mm conversions may be in the works, apparently needing only a modified barrel, with boltface and mag the same as the 5.56x45mm (logically).

6x45 Caliber

We're working on this caliber which is not new but is nevertheless very interesting. The idea behind this caliber is that one modify 5.56 brass and find projectiles from 70 grain to 107 grain. 6mm projectiles have great cross sectional density. The other neat thing about this caliber is that one can use 5.56 bolts and magazines. Corbon will be offering this ammunition.
What do folks think about this development, particularly in comparison to the current 6.8 and 7.62Comm variants, and the back-burnered 6.5?

I've heard great things about 6x45mm as a T/C long-range varmint/target cartridge, but what would the advantage be in an XCR? Is it mainly a fighting cartridge, a long-barrel varminter, or is it decent enough to hunt smallish medium game like pigs and average deer?

Is there any cool subsonic potential with the 107 grains, in terms of being able to spin in the rifling enough to stabilize a heavy bullet, and without having to drop powder charges into the squib danger zone?

I'm certainly intrigued, just a little confused. Then again, if the barrel is the only thing that needs to change, is this maybe just a proposed brief run of a niche cartridge as a "what the heck, let's borrow Joe Bob's 6mm button rifler for the weekend"?
 

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The main advantage as i see it is the ability to swap only the barrel and have a slightly larger caliber that does everything better than 5.56. It would be enough to take deer size game in most places (lots of people use the .243 to hunt). Brass is plentiful and easy to reload, unlike 6.8 and 6.5 which would require new brass. You could use a 6.5 bullet in a 5.56 case but I think you would run out of room for powder due to the size of the bullet.

I am not sure about the subsonic properties of the 6mm, that would take some looking into. I think overall it would make a good deer/pig gun or allow someone to load a slightly larger round than 5.56 without breaking the bank.

See here for more discussion. The thread started as 6.5 talk but changes over the course.

http://xcrforum.com/index.php/topic,1514.0.html
 
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seems like a horrible waste of resources and time when there are much better alternatives out there. IMHO the ability to use 556 brass is a really weak excuse to develop a new cartridge that doesnt have any other advantages over other more prominent and superior offerings like the 6.8SPC

:-[ :2cents:
 

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Good points Jack-O. I am looking forward to the 6x45 so I think differently of course! I got out of the 6.8SPC because of what it was going to cost me to really stock up on what I wanted to have on-hand. At $35 a pop the expenditure alone on an expendable item such as a mag (PRi) was a tough pill to swallow. There's other mags out there and I used them with relative success but were still up there in price comparatively. Shooting price is increased and even with reloading the larger bullets tend to cost more. You'll never hear me disagree that the 6.8SPC has more potential over the 6x45, but the 6x45 allows a shooter to sling a heavier slug with minimum investment.


And as far as subsonic loads, I don't know anything about that but as long as that barrel is threaded 5/8x24 I've got something to thread onto it. There are heavy 6mm bullets you could try it with but that stuff is beyond me at the moment.
 

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I had 3 rifles with 6x45 capability until recently, but sold my Rob Arms M96. I now own two rifles that I load for it. I have loaded from 70 - 85 grain bullets with it, it is easy to load, easy on brass, and flat shoots great. The 6x45 was used as a bench rest cartridge until shooting beyond 300 yards became popular. The Navy Seals liked it and the Air Force tested it. Both services liked it but the dye was struck so we were stuck with the 5.56. Does it run out of gas past 300? No, but it was used as a match cartridge to 300 yards. I have shot deer, wild boar, coyotes, jackrabbits and even squirrel with it (and some pesty armadillos). Will it kill what you shoot with it? Hell yes! If you are near Alabama, come for a visit and we will shoot your (or my) 5.56 against the 6x45. You buy the ammo though. :duh: >:D :popcorn:
 

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Discussion Starter · #6 ·
IMHO the ability to use 556 brass is a really weak excuse to develop a new cartridge


New? My father was just starting to shave when the 6x45mm came out, and I'm almost 30.


seems like a horrible waste of resources and time when there are much better alternatives out there.
I'd imagine it's a pretty minimal investment compared to most of RobArm's other brainstorms. They're just taking the same barrels and drilling them with a different rifling button or whatever. Everything else is compatible with the .223 version, though maybe there's some difference in the ports of the gas adjust. Correct me if I'm wrong, but it seems like a relatively straightforward development process, compared to many others ideas they've pitched.


But I take it that the 6mm bullets heavy enough to do really interesting subsonic stuff are too long to fit an AR mag?
 

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I take it that the 6mm bullets heavy enough to do really interesting subsonic stuff are too long to fit an AR mag?
The heaviest .243" bullet I know of is 115 grains. I don't know if subsonic loads will cycle the action, or not. If loaded into the case with the full ogive exposed, COAL will indeed be too long for the magazine. It might be possible to seat the bullet deep enough for mag-length loads, such as was done with the Mauser-IWK "heavy ball" 5.56x45 ammo circa 1970, but crimping would seem problematical.
 

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Any update on this? What's the story? I would like to know more.
 
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