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Ammunition Discussion Thread

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14 hours ago, Vicious_CB said:

 

I heard from a little bird that the mechanism for yaw independent fragmentation has to do with fluid expansion starting in the gap between the penetrator and jacket. Perhaps there is a ideal location to optimize flow into the gap to initial expansion. 

 

That's my understanding. Since the gap adds significant drag, that suggests optimum design would be either a compromise between drag and hydraulic expansion to produce maximum frag range, or would use a different, low-drag exploit to initiate fragmentation (like Mk. 318 does). Regardless, there's no reason a design with fragmentation velocities much over 1,900 ft/s would be necessary, so I use that figure in my evaluations.

 

It's also possible that even a closed-gap design like the Hornady A-Tip would have a low MFV, and you wouldn't need such a big gap.

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My high pressure rifle cartridge studies have concluded, and, uh, I reinvented the 6mm Unified:

 

bmeQeJ8.png

 

Performance is comparable in terms of operating pressure and energy delivered from a given barrel length. In this case, we're using it to send a 100gr BAT bullet at 3,000 ft/s from a 16.5" barrel. It out-performs all other rounds in consideration, while being smaller and lighter than the others, except the .224 (which is also an excellent performer, but which produced less energy. These subsequent studies intended to find a higher energy solution).

 

These studies have brought me a bit closer to the GPC camp, in an odd way. There isn't enough difference in terms of weight and recoil between something like this and a .224 Valkyrie equivalent to justify the logistics of two rounds. So then, maybe a unified high performance .224 caliber is the best answer (e.g., the .224 Archangel from my post on June 22nd), rather than two separate calibers. You sacrifice a little against this 6mm, but not much in the big scheme of things. And you're still out-performing rounds that are considered high performance even today. 

You could, if you wanted, pair this 6mm with some sort of ludicrously small high pressure round, something like a 4.65mm CETME or .204 Ruger on cocaine. I have my doubts, however, on the ability to make rounds like that in the kind of extreme industrial quantities required, while maintaining the quality control needed for consistent, low drag projectiles. If it came along with the opening of 3+ new ammunition factories, then yes that might be doable.

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Anyone have the skinny on Hornady's 6mm ARC? I like that they're using 6mm VLDs but not a fan of the 6.5G as the base cartridge. Is it reinventing the wheel or is there and actual performance gain. 

 

hornady-6mm-arc-comparison.jpg

1410997146-6mm-ARC---velocity-comparison

1410997145-6mm-ARC---trajectory-comparis

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18 hours ago, Vicious_CB said:

Anyone have the skinny on Hornady's 6mm ARC? I like that they're using 6mm VLDs but not a fan of the 6.5G as the base cartridge. Is it reinventing the wheel or is there and actual performance gain. 

 

hornady-6mm-arc-comparison.jpg

1410997146-6mm-ARC---velocity-comparison

1410997145-6mm-ARC---trajectory-comparis

 

It's basically a factory 6mm AR. Great round.

6mm_PPC.jpg

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I was actually reading some stuff on ammo at TFB, and I have to admit that I'm not the biggest fan of being constrained to the 56mm-57.4mm OAL rounds that the AR-15 and AK-47/47 platforms have proliferated.  However, I really like the .224 Vulcan and 6.86mm Romulan rounds that were hypothetically created.  Both do things well in different ways.  6.86mm is basically a .276 Pedersen capitalistically (which I think .276 is an underrated round), while the .224 Vulcan is a .223 Remington/5.56mm NATO or .224 Valkyrie on roids.  The 6.86 does punch a fairly big hole, while the .224 suits the SCHV with an effective long range round that might be good for use against some forms of body armor at longer ranges.

 

This doesn't take away from modern 5.56mm rounds like M855A1 or Mk 318 or Mk 262, however.

 

But I to think that the rounds mentioned IMO do reinforce my favor or modern modular rifles like the HK433 or the FN SCAR.  For example, I was just dickin' around with a photo scaler/measurer and a photo of an HK433 and also examining some patent illustrations that you can find on Google patents.  I haven't done this with the SCAR yet (and I think that the SCAR 16 wouldn't be the best candidate for this as it is, since I don't know if it can take rounds wider than 5.56mm as far as base/rim diameter), but the 433 it seems can take rounds up to about 66-67mm (maybe longer even, though not much).  Which means from what I can tell it can't take .308 WInchester/7.62mm NATO or 6.5mm Creedmoor or .276 Pedersen without a modded upper, but if you change lowers, barrels and bolts, if the 6.86mm and .224 Vulcan were real, they'd be good round for the 433 and similar modular rifles (the 433 also has clearance bulges on the upper to accommodate rounds at least .447 wide, since it's designed it seems to be rebarreled to 7.62x39mm).  It can also take real life rounds like .280 British or 6x45mm SAW as well.

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22 hours ago, BarnOwlLover said:

I was actually reading some stuff on ammo at TFB, and I have to admit that I'm not the biggest fan of being constrained to the 56mm-57.4mm OAL rounds that the AR-15 and AK-47/47 platforms have proliferated.

 

It builds character!
 

22 hours ago, BarnOwlLover said:

However, I really like the .224 Vulcan and 6.86mm Romulan rounds that were hypothetically created.  Both do things well in different ways.  6.86mm is basically a .276 Pedersen capitalistically (which I think .276 is an underrated round), while the .224 Vulcan is a .223 Remington/5.56mm NATO or .224 Valkyrie on roids.  The 6.86 does punch a fairly big hole, while the .224 suits the SCHV with an effective long range round that might be good for use against some forms of body armor at longer ranges.


I wouldn't get preoccupied with "hole size". Remember, a .270 round creates a hole only 0.053" (1.35mm) wider than a .22 cal round. Also, spitzer rounds, if they do not fragment or expand, do not fly straight into a target. They yaw. The areas of most significant damage within this path will not be at the sides of the bullet, but at the turbulent tip and base as it tumbles through. This rather graphic photo illustrates this more perfectly than I could have hoped for:

Georgian-Conflict-Chest-Wound1.jpg

We don't know by what round this individual was struck, but it's remarkable that from the wound cavity you can tell which direction the bullet was pointing as it passed through tissue. The tip is the most devastating part of a non-deforming bullet, it shears tissue like scissors, as is evident here. The diameter of the projectile, the breadth of literature tells us, does not really have a directly lethal effect, at least within the scope of the sizes normally considered for individual weapons (say .20-30 caliber). 

One of the problems with relying on gel tests alone is that gel, though made of a collagen solution, is not under much tensile stress, whereas human tissues are, being quite literally pulled taught against the muscle attachment points and the skin against the tissues. Lacerating effects in gel show up as barely visible cracks for the most part, but in actual living tissue they result in blown apart tissues, destroyed ligaments, and other dramatic effects. Something worth remembering when thinking about this subject.

And of course, I have not even touched on fragmentation or expansion as lethality mechanisms. Fragmentation results in widespread and extreme laceration which has effects on tissue that very much resemble a meat grinder, including widespread bruising and skin failure in very extreme cases. Since the Romulan and Vulcan rounds all were developed with fragmenting EPRs in mind, it doesn't make much sense to seriously consider the diameter of either round, since if they perform properly (and EPRs almost always do) they won't hold their shape for any more than an inch of gel penetration. A fragmented rifle round doesn't have an overall diameter. 

For EPRs and other fragmenting bullets like SOSTs and BATs (my own invention) what matters much more than diameter is the mass of the disintegrating components (jacket/fragmentation filler), the velocity limit to initiate fragmentation, the angular limit to initiate fragmentation (ideally fragmentation initiates at any striking angle), and the SD of your penetrating components (slug +  penetrator). 6.86mm Vulcan does have some advantages in this regard, which leaves the question: Are they worth the extra weight?

 

23 hours ago, BarnOwlLover said:

But I to think that the rounds mentioned IMO do reinforce my favor or modern modular rifles like the HK433 or the FN SCAR.  For example, I was just dickin' around with a photo scaler/measurer and a photo of an HK433 and also examining some patent illustrations that you can find on Google patents.  I haven't done this with the SCAR yet (and I think that the SCAR 16 wouldn't be the best candidate for this as it is, since I don't know if it can take rounds wider than 5.56mm as far as base/rim diameter), but the 433 it seems can take rounds up to about 66-67mm (maybe longer even, though not much).  Which means from what I can tell it can't take .308 WInchester/7.62mm NATO or 6.5mm Creedmoor or .276 Pedersen without a modded upper, but if you change lowers, barrels and bolts, if the 6.86mm and .224 Vulcan were real, they'd be good round for the 433 and similar modular rifles (the 433 also has clearance bulges on the upper to accommodate rounds at least .447 wide, since it's designed it seems to be rebarreled to 7.62x39mm).  It can also take real life rounds like .280 British or 6x45mm SAW as well.



HK433's lower accepts only 2.26" cartridges. However, I have it on a nudge nudge wink wink confirmation that the 433 was designed to swap between "L" and "H" (7.62 OAL) sized lowers while retaining the same upper/lower junction. We haven't seen an "HK433H" yet but chances are good it at least was on the drawing board.

My large frame design, the F-12 Archangel, was also created with intermediate OAL rounds in mind. It is the primary proposed platform for the 5.56mm Supercruise, as well as the 6.5 Archangel.

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On the HK Pro board, I've been discussing with others if the 433 was designed to take up to 7.62mm NATO/.308 rounds as far as width/OAL.  As far as is known, only the 5.56mm versions have been shown publicly thus far, though they've said for sure that versions in 7.62x39mm and .300 Blackout will be out shortly after the 5.56mm version is released (if it gets adopted by the German Army), and from what I can tell, will likely be available for conversion though different bolts, lowers, barrels and mags. 

 

Also, again messing around with with a photo scaler/measurer, it does seems to be more possible that the 433 upper can maybe take .308 Win/7.62mm NATO with few if any modifications.  Newer measurements I've taken is that the distance between the approx TE of the mag well and where the ending of the front trunnion is indicated on patent drawings indicates a length of 71-72mm.  Not quite enough to fit a .308 in a mag, but then again, I'm being a bit conservative with my measurements.  Of course, it'd help big time if photos of the 433 field stripped and of the upper and lower internals existed. 

 

Someone from HK Pro has said that the reason why this might or might not work out is that POF's .308 chambered AR-15 (not an AR-10, an actual AR-15 upper in .308) was shown to HK designers.  Also, consider this factoid.  An HK433 with a 16.5 inch barrel with a folded stock is 28.23 inches.  A FN SCAR 16 with the same barrel length with a folded stock is only .4 of an inch shorter, which the longer length of the 433 can be at least partly explained in that the stock latch (fixed to the rear of the upper) is counted as OAL, and obviously adds some to the OAL with a folded stock.  And it does have to remembered that HK designed the 433 as a competitor to the SCAR before they pitched it to the German Army to replace the G36.  And as such, it has to bring something new to the table to be a serious competitor.

 

I'd love to know if that was the intention and such.  That all being said, the 433 would probably be a caliber conversion dream.  Though the current lower is restricted to 57.4mm/2.26 in rounds, it does seem that a barrel, bolt and lower/mag swap is very easily doable to many calibers.

 

Also, as to caliber, I know that a lot of people favor the bigger hole theory, which is nice and all.  However, smaller caliber rounds are lighter, flatter shooting, when done right they have a ton more stopping power and lethality than their size suggest (after all, game significantly larger than human sized has been taken down by .223 Rem/5.56mm NATO), and as you've pointed out on a blog I commented on, smaller caliber HV rounds do tend to yaw/tumble more readily in a shorter distance vs larger caliber rounds, which all spitzer bullets do to one degree or another already.  SCHV just tend to do it better and quicker.

 

 

 

 

 

 

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