6.2mm OCC

I understand that most would use 6mm to designate a .243" bullet, But a 5.56mm is not really 5.56mm it's 5.6896, so it's closer to 5.7mm. .223rem is .224". This could go on and on and on. So 6.17mm = 6.2mm

Click to expand...

...but, the cartridge caliber designation is typically based upon the bore diameter which in the case of .223Rem./5.56NATO is actually pretty close to 5.56mm so that makes sense (at least to me). Same with many others such as .45cal. pistols and rifles, both have a approximately .450in. bore, though they shoot .452in. and .458in. projectiles respectively. In short there is no well accepted naming convention, but by military standards the bore is often the basis for the cartridge designation.

Fully confused yet?

Did everyone give the 5.7x28mm hell also for not calling it 5.56x28mm?

Click to expand...

No, I think they gave that hell, for having performance roughly equal to that of a .22WMR rifle. Haven't gotten around to how bad they named it.

It is very confusing when you dig into it.

Click to expand...

Yep.

Congrats on your success, hopefully there will be additional good news to follow.

Yep, not doubt he will soon be forgotten...Art will come along and banish him.

Here are some ballistics figures just to give an idea on how this will compare to the 6.8 and 6.5.

First, your 75 grain bullet with a claimed bc of .330 out to 600 yards starting at 3000fps.

Range Velocity Impact Drop ToF Energy Drift
0 3000 0 0 0 1499 0
25 2919 0.39 0.18 0.03 1419 0
50 2847 0.53 0.61 0.05 1350 0
75 2776 0.41 1.3 0.08 1283 0
100 2706 0 2.28 0.11 1219 0
125 2637 -0.7 3.56 0.14 1158 0
150 2569 -1.72 5.15 0.16 1099 0
175 2503 -3.08 7.08 0.19 1043 0
200 2437 -4.78 9.35 0.22 989 0
225 2373 -6.85 11.99 0.26 938 0
250 2310 -9.3 15.01 0.29 889 0
275 2248 -12.17 18.45 0.32 842 0
300 2186 -15.46 22.31 0.35 796 0
325 2126 -19.21 26.63 0.39 753 0
350 2066 -23.45 31.44 0.43 711 0
375 2007 -28.18 36.75 0.46 671 0
400 1950 -33.46 42.6 0.5 633 0
425 1893 -39.32 49.03 0.54 597 0
450 1838 -45.79 56.07 0.58 563 0
475 1784 -52.89 63.74 0.62 530 0
500 1731 -60.68 72.1 0.66 499 0
525 1679 -69.2 81.19 0.71 469 0
550 1629 -78.49 91.05 0.75 442 0
575 1579 -88.6 101.73 0.8 415 0
600 1532 -99.58 113.28 0.85 391 0

Okay, now a 110 grain bullet from a 6.8 going at 2600 fps with a bc of .32

Range Velocity Impact Drop ToF Energy Drift
0 2600 0 0 0 1651 0
25 2525 0.52 0.23 0.03 1557 0
50 2457 0.72 0.79 0.06 1475 0
75 2390 0.55 1.71 0.09 1395 0
100 2325 0 3.02 0.12 1320 0
125 2261 -0.96 4.73 0.16 1249 0
150 2197 -2.34 6.87 0.19 1179 0
175 2135 -4.18 9.46 0.23 1113 0
200 2073 -6.48 12.52 0.26 1050 0
225 2012 -9.31 16.1 0.3 989 0
250 1953 -12.66 20.21 0.34 932 0
275 1895 -16.59 24.89 0.37 877 0
300 1837 -21.12 30.18 0.42 824 0
325 1782 -26.31 36.12 0.46 776 0
350 1727 -32.17 42.74 0.5 729 0
375 1674 -38.77 50.09 0.54 684 0
400 1622 -46.14 58.22 0.59 643 0
425 1571 -54.35 67.18 0.64 603 0
450 1522 -63.42 77.01 0.68 566 0
475 1475 -73.44 87.78 0.73 531 0
500 1429 -84.45 99.55 0.79 499 0
525 1386 -96.54 112.39 0.84 469 0
550 1344 -109.74 126.35 0.89 441 0
575 1305 -124.16 141.52 0.95 416 0
600 1267 -139.83 157.95 1.01 392 0

Your cartridge never beats the 6.8 in energy at all even with an advantage of 400 fps!!!


And now a 123 grain bullet from the 6.5 grendel with a BC of .55 shot at 2500

Range Velocity Impact Drop ToF Energy Drift
0 2500 0 0 0 1707 0
25 2458 0.55 0.24 0.03 1650 0
50 2419 0.74 0.84 0.06 1598 0
75 2381 0.56 1.81 0.09 1548 0
100 2343 0 3.16 0.13 1499 0
125 2305 -0.96 4.91 0.16 1451 0
150 2268 -2.34 7.08 0.19 1405 0
175 2231 -4.14 9.67 0.22 1359 0
200 2195 -6.37 12.69 0.26 1316 0
225 2158 -9.06 16.17 0.29 1272 0
250 2122 -12.21 20.12 0.33 1230 0
275 2087 -15.85 24.55 0.36 1190 0
300 2052 -19.99 29.48 0.4 1150 0
325 2017 -24.65 34.93 0.44 1111 0
350 1982 -29.84 40.91 0.47 1073 0
375 1948 -35.59 47.45 0.51 1036 0
400 1914 -41.91 54.56 0.55 1001 0
425 1881 -48.83 62.27 0.59 966 0
450 1848 -56.36 70.59 0.63 933 0
475 1816 -64.53 79.55 0.67 901 0
500 1783 -73.35 89.16 0.71 868 0
525 1752 -82.87 99.47 0.76 838 0
550 1721 -93.08 110.47 0.8 809 0
575 1690 -104.04 122.22 0.84 780 0
600 1660 -115.75 134.72 0.89 753 0

As you can see the 123 grain bullet from the grendel beats the heck out of both of them for range, energy, and trajectory.

Now, why dont you just take the .223 casing and put a 6mm bullet in it? Cause its already been done!!!!! How much more powder capacity does the new casing give you? Looking at the dimensions, it probably wont get you any more at all. Sorry, but your idea would take way too much work to get it to perform the same as the 6mmx45.

Sorry if I sound like a jerk, but I just don't see an advantage to this cartride.

How can anyone improve or try to improve on an item, in this case a 5.56 to try and make it better, maybe it will or maybe not, but if a person has a dream to do something
like this you should not be knocking him, you ought to be applauding this person, you should give him your support instead of all your negative waves Moriarity.

Ron

Sorry if I sound like a jerk, but I just don't see an advantage to this cartridge.

Click to expand...

I somewhat feel the same way...however my desires (in a cartridge), and the needs of the military are two different things. I believe this may be a winner for general military use, while I would prefer a 6.5Grendel to meet my needs (in an AR-15 platform anyway). You see this as what can it do that the 6.5/6.8 can't (which is little), but it has some nice advantages such as approximating the speed of the 6.5Grendel, and the energy of the 6.8SPC, while doing so with less powder, less weight, smaller size (greater magazine capacity), and less drop at combat ranges.

It suits the role pretty well, I think the biggest hurdle is that the 5.56NATO does a reasonably good job...so why replace it at a fairly great cost? I think this would be a great option if (and when) we decide to replace the current M4, but until then I don't believe that the brass will be open to any cartridge.

I think this would be a great option if (and when) we decide to replace the current M4, but until then I don't believe that the brass will be open to any cartridge.

Click to expand...

Nah. 70-75gr just doesn't cut it. You need a bigger chunk of metal. Just enough is not always enough.
The designer of the 6.8Spc, Mr Cris Murray just posted the specs for his 7x46mm UIAC. Case and chamber drawings and some specs.

http://cid-4e0b456cafea6a74.skydrive.live.com/browse.aspx/.res/4E0B456CAFEA6A74!147

That's a cartridge worth switching to. It could do the job of both 5.56 and 7.62NATO with one cartridge.
No strings attatched to the old platform. Designed from the ground up to combine both worlds in one package.
Basically, the 7.62x39mm Russian case extended to 46mm and necked down to 7mm. Pushing a 130gr, .411BC, projectile at 2650fps from 16.5" barrel. Plenty energy across the whole range and maximized terminal performance.
You would never feel outgunned again.

I have to say that 7mm sounds pretty tasty too...I would love to see the numbers (may have been in the link, but it didn't work for me).

You have there links to two .pdf and one power point docs. If you click for example on "7x46mmUIAC DOC1", a new page opens and you have on the left the "download" link. Is a pdf that contains case and chamber specs.

Here's some stuf on in those docs:



"The 7x46mm was designed as a single replacement for our current two cartridge system.
1. The 7x46mm UIAC is
a. Designed to used a 8,4 g. (130 gr.) FMJ projectile having a length of 28.5mm (1.1220 in.), having a BC of .411 or better.
b. Maximum cartridge over-all-length (AOL) 64.262mm (2.530 in.)
f. Designed for 7mm Mauser bore diameters of 6,98mm bore, 7,24mm groove, having 4 grooves at a 1:297mm (1:11 in.) twist rate.
g. Can be used in 7mm American bore diameters of 7,04mm bore, 7,21mm groove provided proper reamer bushings are used.
2. Pressure specifications of the 7x46mm UIAC are the same as 7.61x51mm NATO/EPVAT
a. Maximum Service Pressure (Pmax) 4150 bar (60,190 psi)
b. Peak Maximum Service Pressure (PK) 4772 bar (69,218.5 psi) Pmax + 15%
c. Proof Pressure (PE) 5190 bar (75,275 psi) PK + 25%



7x46mm UIAC

Sight Height: 1.5 inches Bullet Ballistic Coef.: .411
Target Range: 500 yards Muzzle Velocity: 2650 fps
Altitude: 500 feet Bullet Weight: 130 grains
Temperature: 50 Fahrenheit







"

One must remember how much ammo one can carry with them, lite weight is good, ala
5.56, this 6.2 appears to pack quite a punch both in close and at distance, but do not know what would be comfortable amount to carrry, it also seems to fit in existing mags
as well, so just changing out the upper is all their is, cost would be down as well, pluw the number that would come on the open market, just some thinking going on here.

Ron

I don't know how well will fit in 5.56 mags. Remember, 6.8SPC and 6.5 grendel suposed to work flawlesly in regular AR mags.

Remember, 6.8SPC and 6.5 grendel suposed to work flawlesly in regular AR mags.

Click to expand...

Huh? If that is the case there are a lot of unnecessary and [comparatively] expensive magazines that are specifically designed for the aforementioned cartridges (and the only cartridge that I can think of that doesn't is the .458SOCOM). I don't think that designing a new magazine would be a big hurdle, heck you already have to swap the bolt and bbl.

I don't see people carrying AK's complaining about mag capacity. 7x46mm uses the same brass just longer. About recoil I don't know. I shot few years ago an old czech rifle chambered in 7.62x45mm (130gr. bullet) and recoil was surprisingly mild. That was originaly proposed as base case for 7x46UIAC. Just necked down to 7mm.

Huh? If that is the case there are a lot of unnecessary and [comparatively] expensive magazines that are specifically designed for the aforementioned cartridges (and the only cartridge that I can think of that doesn't is the .458SOCOM). I don't think that designing a new magazine would be a big hurdle, heck you already have to swap the bolt and bbl.

Click to expand...

I was just joking. That's how they were advertized first. Of course they didn't quite work from regular 5.56 mags.