The Ultimate Combat Round

[GunTech]

Jorg, I had the same question. 50,000 PSI is about the reasonable maximum in most modern assault rifles. Grendel specifically warns users about hot loads in the AR platform.

Nolo, Can you give me exact dimension on your cases? I'll runs them through QuickLoad. In the 6.5x50 round I worked on a couple of years ago, with a water capacity of 37 gn H2O, the best I could do was 2775 fps with 45,000 PSI

The 6.5x47 Firebrand shows a case head size of 10.3mm, or 0.403 inches - which is between 223 (0.383)and 6.8 (0.422). My own 6.5x50 uses a 0.452 casehead and in order to make 3000 fps using requires a chamber pressure of 66,000psi. The 6.5x47 Firbrand would have less case capacity so the pressure must be higher, likely into the 70,000 psi range.

 

[gipperdog]

To reach velocities of 3000 fps from a 6x43 on a 100 grain bullet, your pressures would be way too high for any kind of assault rifle. That's why I asked earlier concerning the 2400 to 2500 fps on an 18" barrel which would be more realistic. I'm not even sure if you can get those velocities with a bolt gun without blowing primers & ruining the brass.
Also, something to consider, utilizing the same case, ie: the 5.56x45 - if you open up the bullet diameter, you can achieve greater velocities with same bullet weights than the parent cartridge can. See the 30-06 compared to the .338-06 with 180 grain bullets. A standard "benchmark" load for the 30-06 with the 180 gr bullet is 2700 fps. With the .338-06, you can achieve this same velocity with the 200 grain bullet, 20 grains heavier. And with the 180/185 grain bullets for the .338-06, you can get about 2900 fps.
For a 16 year old, you write pretty well. Keep it up. You're good.

 

[Nolo]

Okeedokee, lemme see...
For 6mm Firebrand:
Base Diameter: .372 inches or 9.449mm
Length of Case Under Shoulder: 1.533 inches or 38.938mm
Length of Case Under Neck: 1.659 inches or 42.139mm
Length of Case Overall: 1.963 inches or 49.860mm
Shoulder Angle: 17.5 degrees
Diameter of Case Opening: .267 inches or 6.782mm
Weight of Projectile: 100 or 110 grains

I'll get the others later, I've got to go, right now.

By the way, (and I have no idea how this happened) the case length for 6mm Firebrand should be 49mm.

 

[GunTech]

Nolo, what are you using for case design?

I'll run up your cartridge in QD, and make some ballpark guesses. That should get us enough for quickload.

Stay tuned.

 

[GunTech]

Gipperdog, you can get better initial velocities by upsizing caliber for the same bullet weight, but you BC generally goes all to hell, so you pay by losing long range performance. There ain't no free lunch.

 

[gipperdog]

Absolutely! There ain't no free lunch. But some trade offs/compromises still make for great cartridges, like the .338-06. You just have know the limitations (& most limitations are the shooter as most guns/cartridges will outperform the person behind the gun.) LOL!
I once read where someone was simply trying to get ultimate velocities not caring for what the BC was. They were shooting a .375 H&H with something like a 135 grain bullet. They achieved velocities greater than 5000 fps.

 

[Neo-Luddite]

Don't Tread on Me--you tread heavily, but speak the truth regarding the politics of citizen-based R&D.

Interesting thread.

 

[Nolo]

For case design, GunTech, it is merely a .30-06 scaled (not necked) down to 6mm.
Also, I'd rather my cartridge have a high BC than go faster. But .30-II is designed to do just what you were speaking of.

 

[Boanerges57]

the 5.7x28 was developed for a very specific purpose that it serves well. It is a round developed for a Personal Defense Weapon (PDW). It is incredibly accurate out to 200m and was designed to penetrate body armor. It is adequate in urban environments and is fairly easy to control in full auto bursts. It is better than a 9mm in most situations. It is a short range round.
The military has been testing 6.5 Grendel. 6.8 SPC doesnt have good enough performance at range to replace 7.62 NATO and the performance difference at closer (ie, urban ranges) between 6.5 Grendel and 6.8 SPC is so small that 6.5 Grendel could be a viable replacement for both 5.56 NATO and 7.62 NATO.
Im sure there will be a lot of criticism of this but I am hoping to have a comparative side by side firing of the major challengers before Christmas. If anyone is interested in being there it will be near Milwaukee. PM or email me for more info.

 

[GunTech]

Nolo.

I haven't done up your 6x43x, but here what it will taker to get a 100 grain 0.243 bullet up to 3000 fps in 6x45mm. Note pressure and loading densities

Cartridge          : 6 x 45 (6-223)
Bullet             : .243, 100, Sierra SPBT 1560
Cartridge O.A.L. L6: 2.260 inch or 57.40 mm
Barrel Length      : 18.0 inch or 457.2 mm

Predicted Data for Indicated Charges of the Following Powders.

Matching Muzzle Velocity: 3000 fps or 914 m/s

These calculations refer to your specified settings in QuickLOAD 'Cartridge Dimensions' window.
C A U T I O N : any load listed can result in a powder charge that falls below minimum suggested
loads or exceeds maximum suggested loads as presented in current handloading manuals. Understand
that all of the listed powders can be unsuitable for the given combination of cartridge, bullet
and gun. Actual load order can vary, depending upon lot-to-lot powder and component variations.
USE ONLY FOR COMPARISON !

1 loads produced a Loading Ratio below user-defined minimum of 90%. These powders have been skipped.

Powder type          Filling/Loading Ratio  Charge    Charge   Vel. Prop.Burnt P max  P muzz  B_Time
                                      %     Grains    Gramm   fps     %       psi     psi    ms
---------------------------------  -----------------------------------------------------------------
Norma URP                          132.2     31.5     2.04    3000    99.3    98037   12731   0.765  !DANGEROUS LOAD-DO NOT USE!
Winchester 760                     125.2     32.0     2.07    3000    97.4    98463   13053   0.764  !DANGEROUS LOAD-DO NOT USE!
Ramshot Hunter                     127.7     32.8     2.13    3000    98.0    98565   13130   0.762  !DANGEROUS LOAD-DO NOT USE!
Ramshot BigGame                    128.9     31.1     2.01    3000    99.9    98812   12439   0.764  !DANGEROUS LOAD-DO NOT USE!
SNPE Vectan SP 11                  125.0     31.1     2.02    3000    99.9    99051   12421   0.764  !DANGEROUS LOAD-DO NOT USE!
Alliant Reloder-22                 139.3     34.0     2.20    3000    94.9    99057   13684   0.759  !DANGEROUS LOAD-DO NOT USE!
Raufoss RA15                       139.3     34.0     2.20    3000    94.9    99057   13684   0.759  !DANGEROUS LOAD-DO NOT USE!
Alliant Reloder-25                 145.2     34.9     2.26    3000    98.0    99092   13803   0.759  !DANGEROUS LOAD-DO NOT USE!
Winchester WXR                     143.2     34.2     2.21    3000    94.7    99190   13703   0.759  !DANGEROUS LOAD-DO NOT USE!
Accurate 4350                      136.3     31.5     2.04    3000    99.3    99336   12519   0.767  !DANGEROUS LOAD-DO NOT USE!
Vihtavuori N560                    138.7     34.2     2.22    3000    92.2    99417   13925   0.759  !DANGEROUS LOAD-DO NOT USE!
Hodgdon H4350                      131.0     31.4     2.04    3000    98.4   100154   12835   0.756  !DANGEROUS LOAD-DO NOT USE!
IMR 4831                           142.4     32.9     2.13    3000    98.5   100994   12725   0.758  !DANGEROUS LOAD-DO NOT USE!
Hodgdon H414                       121.7     31.3     2.03    3000    98.2   101132   12840   0.764  !DANGEROUS LOAD-DO NOT USE!
IMR 4895                           124.5     29.1     1.88    3000   100.0   101333   11598   0.753  !DANGEROUS LOAD-DO NOT USE!
Bofors RP11 ~approximation         123.3     29.7     1.93    3000    99.9   101339   12286   0.766  !DANGEROUS LOAD-DO NOT USE!
Raufoss RA11                       123.3     29.7     1.93    3000    99.9   101339   12286   0.766  !DANGEROUS LOAD-DO NOT USE!
Alliant Reloder-15                 123.3     29.7     1.93    3000    99.9   101339   12286   0.766  !DANGEROUS LOAD-DO NOT USE!
Norma 203B                         123.8     29.9     1.94    3000   100.0   101459   12204   0.765  !DANGEROUS LOAD-DO NOT USE!
Lovex S070                         136.8     32.5     2.10    3000    99.0   101716   12621   0.763  !DANGEROUS LOAD-DO NOT USE!
Hodgdon BL-C2                      116.1     30.6     1.98    3000   100.0   102251   12032   0.763  !DANGEROUS LOAD-DO NOT USE!
Norma MRP 2                        148.2     35.8     2.32    3000    93.1   102566   13908   0.751  !DANGEROUS LOAD-DO NOT USE!
Winchester 748                     114.1     29.6     1.92    3000   100.0   102611   11583   0.759  !DANGEROUS LOAD-DO NOT USE!
Alliant Reloder-19                 137.2     33.1     2.15    3000    95.5   102990   13192   0.752  !DANGEROUS LOAD-DO NOT USE!
Norma 203 old                      124.8     30.4     1.97    3000   100.0   103549   11903   0.764  !DANGEROUS LOAD-DO NOT USE!
Accurate MAGPRO                    138.4     35.5     2.30    3000    90.3   104526   13736   0.748  !DANGEROUS LOAD-DO NOT USE!
IMR 3031                           125.4     28.3     1.83    3000   100.0   104570   11009   0.757  !DANGEROUS LOAD-DO NOT USE!
Bofors RP14 ~approximation         138.2     33.4     2.16    3000    95.6   104621   13088   0.748  !DANGEROUS LOAD-DO NOT USE!
Rottweil R903                      131.7     30.5     1.98    3000   100.0   104963   11777   0.760  !DANGEROUS LOAD-DO NOT USE!
Somchem S355                       128.8     30.4     1.97    3000   100.0   105162   11900   0.759  !DANGEROUS LOAD-DO NOT USE!
Hodgdon H380                       124.0     30.6     1.98    3000    99.4   105393   12296   0.757  !DANGEROUS LOAD-DO NOT USE!
SNPE Vectan SP 9                   121.2     30.2     1.96    3000   100.0   105526   11947   0.754  !DANGEROUS LOAD-DO NOT USE!
IMR 4320                           125.9     29.9     1.94    3000   100.0   105739   11766   0.746  !DANGEROUS LOAD-DO NOT USE!
PB Clermont PCL 516                120.3     30.9     2.00    3000    99.4   106345   12240   0.751  !DANGEROUS LOAD-DO NOT USE!
PB Clermont PCL 507                117.8     29.7     1.92    3000   100.0   106399   11627   0.753  !DANGEROUS LOAD-DO NOT USE!
Somchem S385                       137.4     33.7     2.18    3000    96.9   106471   12664   0.747  !DANGEROUS LOAD-DO NOT USE!
Ramshot TAC                        117.0     29.6     1.92    3000   100.0   106529   11603   0.752  !DANGEROUS LOAD-DO NOT USE!
Accurate 4064                      133.3     30.1     1.95    3000   100.0   106726   11234   0.767  !DANGEROUS LOAD-DO NOT USE!
ADI AR 2209                        135.7     32.6     2.11    3000    95.3   107115   12937   0.742  !DANGEROUS LOAD-DO NOT USE!
Somchem S321                       116.4     29.9     1.94    3000   100.0   107299   11638   0.754  !DANGEROUS LOAD-DO NOT USE!
Accurate 2520                      120.7     30.0     1.95    3000   100.0   107637   11202   0.756  !DANGEROUS LOAD-DO NOT USE!
Norma 204                          130.6     32.5     2.11    3000    95.6   107823   12765   0.741  !DANGEROUS LOAD-DO NOT USE!
Bofors RP4 ~approximation          134.8     32.5     2.11    3000    95.6   107823   12765   0.741  !DANGEROUS LOAD-DO NOT USE!
Raufoss RA4                        134.8     32.5     2.11    3000    95.6   107823   12765   0.741  !DANGEROUS LOAD-DO NOT USE!
IMR 7828 SSC                       136.4     33.8     2.19    3000    92.9   108027   13307   0.740  !DANGEROUS LOAD-DO NOT USE!
IMR 7828                           144.2     33.8     2.19    3000    92.9   108027   13307   0.740  !DANGEROUS LOAD-DO NOT USE!
IMR 4350                           139.0     32.1     2.08    3000    95.1   108189   12687   0.743  !DANGEROUS LOAD-DO NOT USE!
Rottweil R905                      141.7     33.9     2.20    3000    93.1   108278   13014   0.740  !DANGEROUS LOAD-DO NOT USE!
ADI AR 2208                        127.5     29.9     1.93    3000    99.9   108498   11879   0.745  !DANGEROUS LOAD-DO NOT USE!
Hodgdon VARGET                     127.9     29.9     1.93    3000    99.9   108498   11879   0.745  !DANGEROUS LOAD-DO NOT USE!
Vihtavuori N530                    116.9     28.4     1.84    3000   100.0   108556   11398   0.748  !DANGEROUS LOAD-DO NOT USE!
Hodgdon H4895                      128.7     30.0     1.95    3000   100.0   108654   11237   0.743  !DANGEROUS LOAD-DO NOT USE!
Accurate 3100                      148.9     34.0     2.20    3000    98.2   109272   12211   0.740  !DANGEROUS LOAD-DO NOT USE!
SNPE Vectan SP 10                  111.6     28.8     1.86    3000   100.0   109402   11137   0.748  !DANGEROUS LOAD-DO NOT USE!
PB Clermont PCL 508                111.6     28.8     1.87    3000   100.0   109656   11123   0.747  !DANGEROUS LOAD-DO NOT USE!
Somchem S341                       120.3     30.9     2.00    3000   100.0   109734   11549   0.744  !DANGEROUS LOAD-DO NOT USE!
IMR 4064                           129.4     29.5     1.91    3000   100.0   109828   11594   0.744  !DANGEROUS LOAD-DO NOT USE!
Hodgdon H335                       111.3     29.3     1.90    3000   100.0   109905   11150   0.745  !DANGEROUS LOAD-DO NOT USE!
Norma 201                          118.0     29.1     1.89    3000   100.0   110108   11403   0.751  !DANGEROUS LOAD-DO NOT USE!
ADI AR 2213                        137.7     33.6     2.18    3000    93.0   110126   13228   0.736  !DANGEROUS LOAD-DO NOT USE!
Norma 202                          123.2     29.3     1.90    3000   100.0   110535   11090   0.747  !DANGEROUS LOAD-DO NOT USE!
Accurate 2495                      125.5     28.6     1.86    3000   100.0   110802   10775   0.760  !DANGEROUS LOAD-DO NOT USE!
SNPE Vectan Sp 7                   113.3     29.3     1.90    3000   100.0   111203   11096   0.751  !DANGEROUS LOAD-DO NOT USE!
ADI AR 2219                        112.0     27.9     1.81    3000   100.0   111707   10786   0.740  !DANGEROUS LOAD-DO NOT USE!
Hodgdon H322                       119.1     27.9     1.81    3000   100.0   111707   10786   0.740  !DANGEROUS LOAD-DO NOT USE!
Ramshot X-Terminator               114.2     28.5     1.85    3000   100.0   111790   10927   0.743  !DANGEROUS LOAD-DO NOT USE!
Rottweil R902                      126.0     29.3     1.90    3000   100.0   112022   11244   0.747  !DANGEROUS LOAD-DO NOT USE!
Hodgdon Retumbo                    152.3     36.9     2.39    3000    95.8   112249   14030   0.735  !DANGEROUS LOAD-DO NOT USE!
Rottweil R907                      130.9     31.0     2.01    3000    97.7   112840   12210   0.741  !DANGEROUS LOAD-DO NOT USE!
IMR 4007 SSC                       126.8     31.0     2.01    3000    97.7   113007   12200   0.740  !DANGEROUS LOAD-DO NOT USE!
Nitrochemie A/S 0300               110.5     27.4     1.77    3000   100.0   113052   10564   0.742  !DANGEROUS LOAD-DO NOT USE!
Rottweil R901                      123.3     28.3     1.83    3000   100.0   113222   10925   0.749  !DANGEROUS LOAD-DO NOT USE!
Accurate 2460                      114.9     29.7     1.93    3000   100.0   113595   10966   0.746  !DANGEROUS LOAD-DO NOT USE!
Rottweil R904                      137.2     32.6     2.11    3000    94.9   113812   12404   0.731  !DANGEROUS LOAD-DO NOT USE!
Vihtavuori N540                    127.2     31.0     2.01    3000   100.0   114418   11664   0.738  !DANGEROUS LOAD-DO NOT USE!

 

[Nolo]

Hehehe... 90,000-100,000 psi. That's alot. However, I did say before that the case for 6mm should be 49mm long. I don't know how I got 43mm before.
Some other cartridge dimensions:

For 6.5mm Firebrand:
Base Diameter: .403 inches or 10.236mm
Length of Case Under Shoulder: 1.662 inches or 42.215mm
Length of Case Under Neck: 1.799 inches or 45.695mm
Length of Case Overall: 2.127 inches or 54.026mm
Shoulder Angle: 17.5 degrees
Diameter of Case Opening: .290 inches or 7.366mm
Weight of Projectile: 120 grains

For 7mm Firebrand:
Base Diameter: .434 inches or 11.033mm
Length of Case Under Shoulder: 1.433 inches or 36.407mm
Length of Case Under Neck: 1.573 inches or 39.942mm
Length of Case Overall: 1.851 inches or 47.016mm
Shoulder Angle: 20 degrees
Diameter of Case Opening: .283 inches or 7.184mm
Weight of Projectile: 135 or 150 grains

 

[GunTech]

Boanerges57

I understand the rational for the 5.7x28. It may be able to penetrate armor, but from personal experience I can tell you it lack lethality. At 100 yards I has several failures on prarie dogs and rabbits.

A 32 gn bullet going 2350 fps (SS190 from a P90) simply doesn't have adequate energy for military purposes, IMO - even if it does go through a vest. Most of the very light 224 size bullets have a BC of around 0.1. Being generous, I gave the SS190 a BC of .2. At the muzzle, the SS190 has a whopping 382ft-lbs of energy. This is equal to 124gn 9mm ball, true. Of course 9mm ball has an extremely poor record against people - people without the benefit of armor. It should be noted that the 9mm pistol is significantly more compact that the P90. In an apples to apples comparison, the SS90 fired from a FiveseveN manages 2100fps for 313ft-lbs of energy. You are tradining penetration for energy. And by the way, bulletys lose velocity penetrating body armor. Even rounds that penetrate may give up 50% of their energy or more.

By contrast, a 5.56x45 fired from a 10 inch barrel will also make 2500 fps with a 55gn M193 bullet for 764ft-lbs, or 2440 in a 10 inch barrel with M855 62gn for 820ft-lbs.

It is quite possible to build a PDW the size of the P90 that uses 223 ammunition and standard M16 magazines that outclasses the P90 and FiverseveN in every conceiable way. Even the 22 hornet is superior ballistically.

 

[Nolo]

Here is the updated 6mm Firebrand picture:

 

[Nolo]

I'm talking not about performance with the SS190 round, I'm talking about weight!
Yes, I know that the 5.7mm FN round is horribly weak when compared to the 5.56, but not when you use it in quantity! I'm talking about dishing out 7-10 of these rounds at upwards of 2000 rounds per minute! And you can do that adequately because the 5.7mm FN is so much lighter than the 5.56mm, so you can carry 75- or 100-round magazines. Plus, I'm not talking about using the SS190 itself, I'm just using it as a representative of that group.
Now tell me that isn't useful. Sure, it lacks range, but it's darn good for CQB, at the very least!

 

[Nolo]

Don't Tread On Me, that's exactly why I use a Mosin-Nagant. If the the Feds (or anybody else) ever go haywire, I'm fairly certain that my 7.62x54R bullet will be able to penetrate their vests. If you're worried about that, become a rifleman. A real rifleman. Get a friggin' Garand.

 

[dodging230grainers]

interesting stuff, Nolo. I'm only a year older than you and you lost me a few times with the math. Then again I suck at math. Oh, and as for the Glock seeing military service, the Austrian army was the first to adopt it, and they still use it.

As for the ultimate assault rifle combat round in current production...easy.

7.62x39mm Soviet.

And Nolo, I agree that the mosin nagant is the ultimate SHTF rifle. Hey, it won Stalingrad (with cannon fodder techniques)...

Good to see two people from the same generation love the mosin =D

 

[Nolo]

Yes, the Glock has seen service, I know the Austrian Army uses it. But when was Austria in a war? I think the last time was WWI (if you don't count WWII, it was part of Germany during that one). So the Glock has seen service, it hasn't seen combat, as far as I'm aware. Plus, we haven't really seen the true test of plastics: the test of time. Will they wear out? Do they create structural problems later in life? Until I see that they are truly successful, I will stick to the good ole' mostly metal guns. (By the way, it's not the aesthetics of them, I like the way the G36 looks just fine.)

 

[Nolo]

It's an excellent rifle, and it doesn't have all that Mauser pedigree behind it, which I like.

 

[dodging230grainers]

Outside of a small number of contractors in Iraq, I'd say you're right about the Glock seeing combat. It'd be interesting to see what they have to say about how the Glock holds up in the "sandbox".

I think the soviets had it right when it came to small arms. They're the best in the world for the most undesirable purposes.

 

[GunTech]

Nolo, even lengthening the 6x45 to 49mm, to get 300 with a 100gn bullet generates a pressure of 72,000psi. Your cartridge has a smaller base and thus less volume, leading to higher pressure.

I was able to get 3000 fps with suitable (although high) pressure by starting with a 7.62x39 case and increasing the case length to 49mm. By dropping bullet weight down to 90gn (Sierra 90gn FMJBT), pressure was reduced to under 50,000psi. A charge of 38.5gns of H5350 will accomplish the velocity required with a loading ration of 98.6%

 

[Nolo]

Interesting. Well, what velocity would the 6x49mm cartridge get as is?
It seems that the velocity may be scaling with the cartridge, something that I should have expected. If it is, I can only expect about 2300 f/s with the 6x49 Firebrand, which would be highly disappointing to me. And I scaled the cartridge diameter correctly, I believe, but let me double check.
Yep, it's correct, 9.46mm for the cartridge base. That's the base for a scaled down .30-06. Damn, I sure hope the speed is not scaling with the cartridge. That would suck. And, yes, I was thinking about necking up the 5.45x39mm cartridge (which is highly similar to the 7.62x39mm, but not identical) to 6mm, but I was not thinking of lengthening it. That would, in my opinion, make the cartridge have a EPP of not greater than the Grendel (due to the increase in weight), which is the EPP I'm trying to beat.

By the way, yes I did think of scaling the bullet weight of the .30-06, and the weight I have now is actually under the scaled weight (118 grains).

 

[Nolo]

I just found a neat round:
6mm AR. It's basically a 6.5 Grendel necked down to 6mm. It pushes a 105 grain bullet with a better than .5 ballistic coefficient out the barrel at 2900 fps. That beats the Grendel in EPP, I'm sure.
Now why aren't we getting performance like that out of 6x49mm? It seems to me that there's not internal spatial difference. Is it because pressure is greater inside the longer cartridge of the 6x47? If so, let's just neck up 5.45x39mm!

 

[kaizer]

What about the .243? Shoots flat as an arrow and will cover the 400 yards no problem. Easily adapted to the AR platform. More punch than 5.56

 

[Frog48]

I've taken an interest in the 6.5 Grendel lately.

Hopefully its not just a passing fad, but unfortunately aftermarket support (thus far) has been minimal at best, so it could eventually be nothing more than a novelty.

 

[zinj]

I think .250-3000 Savage would make an excellent service rifle round. It can be loaded with bullets from 87 to 115 grains, has a standard .473in case head, is fairly compact and has moderate recoil. Unfortunately it was invented in 1915 and doesn't have a sexy metric designation, so it would never be adopted.