The Ultimate Combat Round

[Tony Williams]

Yes, Tony Williams, recoil can be a non-issue if we choose the right weapon. In otherwords, a weapon that either uses constant recoil, the laterally moving breechblock system or a balanced action.

Some such devices may change the nature of the recoil kick experienced by the shooter (by making it softer but longer, as opposed to short and hard), but there's no escaping Newton's Third Law (for every action, there's an equal and opposite reaction). Only a muzzle brake or suppressor will actually reduce the recoil impulse generated by firing a cartridge.

 

[Nolo]

No, muzzle brakes will not, TW, they, just like all of these other methods, merely reduce felt recoil. The recoil is still there. Nevertheless, reducing felt recoil allows your rifle to fire longer on full auto, keep on target and do important things like shove more rounds into more important parts of your enemy. Just watch videos of the KRISS and AA-12, and tell me that they don't work (which, to me, seemed to be what you were impying).

As for all the money issues, I never said anything about the U.S. miltary adopting this technology. Just check, I never did. I'm not going to go over it, I don't recall saying it, so I'm pretty certain that I never did in this thread.

I'm merely trying to optimize.

 

[Tony Williams]

No, muzzle brakes will not, TW, they, just like all of these other methods, merely reduce felt recoil. The recoil is still there.

Sorry, but you are wrong there. Recoil is generated by two elements: one is the bullet weight and muzzle velocity, the other is the propellant weight and the velocity of the gasses as they escape the muzzle - a kind of "rocket effect". In a typical high-velocity military rifle cartridge, about 30-40% of the recoil impulse comes from the propellant gasses. So if you can stop these gasses from rushing forwards but turn them to one side (or even better, to the rear) you will lose the rocket effect or even turn it slightly to your advantage. And that's what a muzzle brake does.

Of course, you can never trap all of the gasses - some will escape through the hole in the muzzle brake which the bullet passes through, others will pass on either side of it - but a good design can significantly reduce the actual recoil. If it is arranged that a part of the gasses vents upwards (as with the AK-74's brake) then the downward push helps to counteract muzzle rise as well (in that instance, it's acting as a compensator as well as a brake).

Suppressors trap and slow down much of the gas, letting it leak out of the gun more slowly, so they reduce recoil as well.

You can find out how to calculate the two different elements of recoil in this article on my site: http://www.quarry.nildram.co.uk/ballistics.htm

As far as gun design is concerned, this can have a minor effect on actual recoil (a gas-operated gun bleeds off some of the gas which would otherwise be rushing out of the muzzle), but most of the effects are concerned with reducing the perceived recoil, usually by smoothing out the recoil pulse over a longer time period. The benefits can be considerable, but the firer still gets pushed back by the same force. The shape of the stock is also important in affecting perceived recoil.

 

[GunTech]

There's also 'soft recoil' systems - primarily used on artillery, but employed on weapons like the XM-307/XM-312. In this case, the barrel and action are held to the rear under spring tension. On firing, the barrel and action are released, flying forward and firing when the action and barrel have attained maximum velocity. Recoil has to overcome this forward momentum, significantly reducing recoil.

Whether this technique can be utilized successfully is another matter. A well designed muzzle brake is much simpler.

How much difference will a muzzle brake make? As Tony noted, recoil is caused by both the bullet and the escaping propellant. In the case of our 6.5x45 round, lets look at the before and after, assuming a muzzle brake that completely eliminates the effect of the propellant gases (ideal case).

Again, the reference rifle weighs 9 pounds.

Bullet	Ipulse	Free Recoil	Free Energy
M855	1.3	4.5	2.9
6.5 w/o	1.9	6.8	6.5
6.5 w	1.4	4.8	3.3
M43	1.9	6.8	6.4
M80	2.5	8.9	11.1

Naturally, it is unlikely that 100% of the recoil created by the escaping propellant gases will be eliminated by the brake, but a well designed brake will have a large impact on recoil (as anyone who has fired one of the various 50 caliber rifles can attest.)

Note in the above, the braked 6.5 has less recoil than the 7.62x39mm and only slightly more than the 5.56x45mm.

If anyone doubts that recoil brakes work, here's a rather poor video of a test of a muzzle brake I designed, fitted to an aluminum receiver FAL weighing a mere 7 pounds. Please note that I am firing this rifle off my chin. Without a brake, this rifle should generate a recoil impulse of 2.5 lbs-sec, a free velocity of 11.5 fps and a free energy of 14.4 ft-lbs.

http://www.guntech.com/muzzle/muzzle_mpeg2.html

Here's a close up of the barke in question:

Tod

 

[Nolo]

They reduce felt recoil by counteracting the recoil the rifle through redirecting the gases. Recoil is just about impulse, the opposite impulse from the energy of the round, which there are various ways to counter.

Either way, there are known ways to counter it, so the discussion is moot.

 

[Oohrah]

Presently a report states that 30,000 rounds are used per target. Marine
NCOs have given up their M9 and they have been replaced with A-4
rifles. We are giving supposedly friendly Iraqi troops M-16s in trade for
those AKs. At distance, the 223 is the same no bullet energy crap that
it always has been, even with all the modifications made over the years.
Double tap training kind of proves it is not an effective round in it's
ball form. Makes you wonder why there is a shortage of this not so
great round? Is it because the amount of rounds expended per target,
or because we will arm potential enemies. Pretty sad when our main
supply of ammo comes from other countries like Israel to take up the
slack. Wonder if we still get our combat boots from China!!! There
was nothing wrong with the 7.62x51. Why we got into a less effective
mode is beyond me. I think the spray and pray has put us back to
where they have to fix don't work to may work!

 

[GunTech]

7.62x51 is not usable under full auto, and weighs too much. Remember, 90% of all infantry fire occurs at 300 yards or less, 80% at 200 yards or less and about 70% at 100 yards or less, regardless of terrain. During WWII, the average range of engagement was about 70 yards.

There are times such as assaulting where auto fire is appropriate. It's also useful for fixing the enemy during fire and maneuver. The effectiveness of 'aimed fire' under combat conditions is overrated.

I'll quote myself from another post on the subject

The assumption of long range performance is based on what I call the "Rifle Range Mentality". The fact of the matter is that studies have consistently shown that the infantryman is not able to engage target over about 300 meters, regardless of how accurate the weapons is *(note that this is infantry combat, as opposed to sniping).

The whole rationale of the assault rifle is built around this fact. The reality is that most rifle fire occurs at 100 meters or less. *I've posted more detailed explanations of this on this list before. Those conclusions (and other more interesting ones) are drawn from Hitchman's "Operational Requirements for an Infantry Hand Weapon". Hitchman based his analysis on the ALCLAD study.

During the Korean war, as study on the effectiveness of body armor was commissioned and was later known as ALCLAD (sorry, I don't know what that stands for). One of the factors that became apparent during ALCLAD was that there had never been a detailed analysis of how hits are incurred in combat. Careful analysis was made of all casualty reports from WWII and Korea (data from Vietnam and the Arab-Israeli conflicts was later added and proved the validity of the model.

Hitchman and the ORO made use of this data for their report . Many of their conclusions were controversial, but to date no one has been able to dispute them scientifically. Here are some of the relevant quotes. As the 'Fireside Theater' said, everything you know is wrong.

Quoting Hitchman (and with my own comments):

"Rifle fire and its effects were deficient in some important military respects...in combat, hits from bullets are incurred by the body at random:..the same as for fragment missiles..which are not 'aimed'...Exposure was the chief factor...aimed or directed fire does not influence the manner in which hits are sustained...[Despite] evidence of prodigious rifle ammunition expenditure per hit,..the comparison of hits from bullets with those of fragments shows that the rifle bullet is not actually better directed towards vulnerable parts of the body"

If time and degree of exposure was the chief factor in whether a hit was obtained, what was the point of long range shooting? Further, analysis of actual combat in showed that 90% of all rifle fire occured at 300 yards or less and that 70% occurs at 100 yards or less. Interveneing terrain, camouflage and an inability to adequately identify targets were cited. Indeed, the effectiveness of rifle fire drops rapidly to zero at ranges greater than 300 yards.

Hitchman continues:

"It is interesting..that at all common ranges weapons errors are without significance in the man-weapon system...the dispersion of the weapon could be more than double without materially affecting the probability of hitting the target...weapons-design standards which seek perfection by making the rifle more accurate (approach zero dispersion)..are not supported by this analysis as genuine military requirements. Errors in aiming have been found to be the greatest single factor contributing to the lack of effectiveness of the man-rifle system...[in combat] men who are graded..as expert riflemen do not perform satisfactorily at common battle ranges."

"Either a simultaneous [salvo], or a high cyclic rate burst, with the number of rounds per burst automatically set rather than be dependant on the trigger release. In the (single barrel burst) design, controlled nutation [nutate: to nod or droop] of the rifle muzzle would provide the desired shot dispersion or pattern; in the..(salvo), the scatter would be obtained and controlled by multiple barrels, a mother-daughter type of projectile, or projection of missiles in the manner of a shotgun."

 

[Nolo]

That is the reason for this thread; to improve the effectiveness of the combat rifle.

GunTech, could you run me a 5.45x39mm round necked up to 5.75mm with a 80, 85 and 90 grain bullet? What kind of speed and energy do I get?

 

[GunTech]

They reduce felt recoil by counteracting the recoil the rifle through redirecting the gases. Recoil is just about impulse, the opposite impulse from the energy of the round, which there are various ways to counter.

Actually, propellant gases cause about 1/3 of the of the recoil generated. Bear in mind that Newtons law require an equal and opposite reaction. It not just the bullet going down the barrel, but anywhere from 25-50 grains of powder, converted to combustion products and moving at around 4000fps.

If you redirect the gasses, their forward momentum does not contribute to recoil to the same extent. If you direct the gasses rearward, it can actually counter act the recoil generated by the bullet.

 

[GunTech]

Presently a report states that 30,000 rounds are used per target.

That means troops are getting better. The ratio in Vietnam was closer to 1000,000 round per casualty.

BTW, those number are deceptive. The vast majority of rounds are spent fixing the enemy, providing cover and suppressive fire and basically trading ammunition expenditure for casualties. I'll gladly burn ammo to save servicemen's lives.

The low rounds count per casualty ration in WWI (7,000 rounds per casualty) is miore reflective of the iddiotic tactics of the time than superior marksmanship.

30,000 round per casualty is about equal to WWII, and better than KOrea and Vietnam.

Do you have a cite for this data? This reflects a radical change in ammo expenditure per casualty.

 

[Nolo]

Okay.
My point was, it works.
We know it does. So there is no reason to bicker about why.

 

[GunTech]

GunTech, could you run me a 5.45x39mm round necked up to 5.75mm with a 80, 85 and 90 grain bullet? What kind of speed and energy do I get?

Unfortunately, I am stuck with bullets in the database, so unless I build a 5.75 bullet, such a task isn't doable.

It should be noted however that without changing the allowable pressure or case capacity, minor changes in bullets won't have much of an effect. You can trade things like short range energy for long range performance, but ultimately, you are just trading back and forth, not gaining.

A good example is the 6.5 Grendel. There are some good gains over the 5.56 because you are blowing out the case and sharpening the shoulder, and running the cartridge severa thousand psi over the 7.62x39mm. That will make a difference.

Now consider the 6x45 vs the 5.56x45 - the same case necked up to 243.

Muzzle velocity drops, meaning less muzzle energy. You trade short range energy for long range energy because the 243 bullets tend to have much better BC. You can also adopt a 223 bullet with better bc, and you get similar performance.

6.5 bullets, at moderate weights, tend to have very good BC. If yourt drive them at relatively decent velocities the have plenty of energy, and retain it well. Note that the 308 has much more energy, but the existing ball ammunition has relatively poor BC, so that the 6.5, starting slower and with less energy than the 308, eventually surpasses that cartridge (at around 500 yards)

There are high BC bullets for 308, but these tend to be heaver, meaning more recoil, every thing else being equal.

The real trick is to develop a cartridge that does a lot of things well, even if it doesn't do one thing really well. It a case of generalization versus specialization. If you have one round for machine guns, one for assault rifles, one for DMR and one for snipers, you can optimize each one for that one specific job. Of course, you've created a logistical nightmare, because now you have to supply 4 or more catridges.

Logistics is a huge factor in winning wars. So build you cartridge right, and possibly you can hace one round that performs pretty well in an assault rfile, not too bad in a machinegun, fairly decent in a dmr rifle and adequate as a sniper round.

And that is a very good thing.

The 6.5x45 decribed above is going to be a little too powerful for light and compact assault rifles - you are going to want to add a brake. It will be great for semi-auto fire, but much less contyrollable in autofire than 5.56.

In a full sized rifle with a 20 inch + barrel, it will do very well at intermediate range, and with good sectional density, shoud be good against walls and such.

Put it into a 24 inch DMR, or a prescision built 26 inch sniper rifle and it should be plenty accurate. If necessary, and where recoil isn't a factor, you can load the same round with a heavy, very high BC bullet and get long range performance that rewally shines - superior to M80, and very clode to M852 or M118LR special ball.

The rifle requires no change, and can be based on the same platform as the basic military rifle - highly refined and with match grade parts. in a pinch, the sniper can still shoot the general issue ammo, just losing some accuracy and long range performance. This is much more desireabe than issuing a completely separate catridge with a separate logistical train.

One Round to rule them all, One Round to find them,
One Round to bring them all and in the darkness bind them."

 

[Nolo]

Here's how I see it as far as logistics is concerned:
2 rounds. Make two rounds, each specialized to the opposite ends of the spectrum. DMR (I am excluding sniper because they are already specialized and can make their own choices for ammunition) and GPMG effectively can use the same round. There is not enough difference there (in my mind) to warrant a separate cartridge for each. You can (and should) also cater that cartridge to snipers because it is easy, DMRs are pretty close to sniper requirements. I think that for those missions, a 7mm or 6.5mm bullet is ideal, with a case between the 6.5 GunTech's and the 7.62 NATO's. So that leaves PDWs and assault rifles. They can easily share a round, if one uses a low-end cartridge like 5.56 or 5.45. So I'm basically, at this point, focused on improving that cartridge. How I think that might be achieved is by improving the bullet of the 5.45x39mm cartridge, and the first idea I had was necking up to 6mm, but that proved to be too much. So now I'm thinking of somewhere in between. Well, exactly in between is 5.75mm, so that's why I asked about that. I want to see the data for 80, 85, and 90 grain bullets as pushed by that case. The closer you can get to 5.75mm for the bullet, the better. 5.8 would work.

Also, can you give me a comparison of the powder capacity of the 5.56mm case and the 5.45mm case? I'd very much like to see which one has more powder.

 

[Nolo]

Here are some calibers that would work, provided they had the proper weights:
.225
5.6
5.7
5.8
But, again, I don't know what the bullet weights for those are.

 

[GunTech]

If you are going to have two cartridges, there's little reason to change the current 5.56x45mm and 7.62x51mm, IMO.

 

[Nolo]

Little reason, yes, GunTech, but I don't need a reason to develop something. Most often you will find that I do stuff because I can. I can make a better bullet, and I want to. Plus, I'm trying to beat the 52000 EPP of the 5.56. That's a big enough reason for me.

 

[JWarren]

Nola,

I see your reasoning on the term 'Gun hose." It's something to think about. It may be a good idea to start a seperate thread to consider this and any terminology associated with it.

Putting it in this thread would take away from the quality discussion you guys are having here. Thanks for this, and thanks for clearing up the "Gun hose" reasoning.


-- John

 

[Nolo]

You're quite welcome.
This thread was solely about the assault rifle anyway, and I was going to start a thread on the other two later, so I may just do that.

 

[Bigfoot]

Look at the 6.5x52mm Carcano case. A tiny bit wider than the 7.62x39 and 6.5 Grendel so it fits and feeds well in 6.5 G magazines after shortening. New brass is available from Norma.

 

[raubritter]

If I was really going to standardize an assault rifle cartridge, it would simply be the 7.62x39 necked down to 7mm, using a 100grn steel core. That would have a good BC and shoot flatter.

 

[Nolo]

The beef I have with that is weight. I bet it wouldn't exceed the EPP of the 5.56mm.
Feel free to calculate it for me.
Really, the Grendel case is about as wide as I want to go, so too with the Carcano case. I'd shorten it up anyway, which would end up being basically the same thing as the 6.5x45 GunTech.

 

[GunTech]

If I was really going to standardize an assault rifle cartridge, it would simply be the 7.62x39 necked down to 7mm, using a 100grn steel core. That would have a good BC and shoot flatter.

In the 100 grain range, the 6.5 has a better BC than the 7mm by a pretty good margin. Why not take a 7.62x39, neck it down to 6.5, and blow the case out to near 'improved' standards.

Crap - we just reinvented the 6.5 grendel

 

[Nolo]

Excellent point, GunTech.
Actually, I would like an AK in 6.5 Grendel, will they start making them soon?

 

[Nolo]

Found some very exciting data a minute ago.
Really just realized it had been there all along.

The USA is undertaking a Lightweight Small Arms Technologies development programme, with the aim of halving the weight of the current 5.56 mm M249 (FN Minimi) LMG and its ammunition. Two different cartridge designs are being tested, shown here in comparison with the 5.56x45 (top). In the middle is a polymer-cased telescoped round (by ARES), and below that a caseless round (by ATK) based on HK G11 technology. The linked polymer-cased rounds are showing a 33% reduction in weight over conventional 5.56x45 ammunition, the caseless rounds a 51% reduction. The initial calibre and ballistics have been chosen to match the 5.56x45 SS109/M855 for comparison purposes, but in parallel with this, research is being carried out into using the weight savings to produce a "Company" MG which might replace both 5.56mm and 7.62mm MGs.

Basically, what this means is the EPP of these cartridges is shooting way, way up. Makes me feel kind of stupid for discounting caseless ammunition now. Actually, really stupid.
EPP of 5.56x45mm: 52000 (approx.)
EPP of 5.56 Telescoping: 79000 (approx.)
EPP of 5.56 Caseless: 102000 (approx.)
Those are some stunning figures!
So, here's the question: what problems do caseless cartridges have? Can you have caseless cartridges that fire using caps? I heard that HK (or whoever they had doing the work for them) basically solved the problems associated with the caseless ammunition, but I was wondering if there was any opposition to that statement.

 

[GunTech]

It won;t make you feel stupid when you realize what a pain it is to make caseless ammo work. People don;t aporeciate all the wondeful thikngs the case does. It protects the round from rough handling and non-ideal environmental conditions. It extracts heat from the chamber. It obturates - that is - expands to seal the chamber, and then shrinks slightly so it can be removed fairly easily. It gives the extractor something to grab. Without the casing, you have to deal with all this stuff.

How do you seal the breech?
How do you deal with the extra heat in the chamber
How do you keep the propellant from being damaged by water, oil, heat and cold, etc, etc. ?
How do you protect the integrety of the round from the mechanical handling of the action itself?

It's not as easy as people thing. How many caseless autoweaopons do you see out there - particularly in rifle calibers? It's an attractive solution - ne that has been in development for the military for at least 50 years.

IIRC, there are a couple of aircraft canon that iuse caseless ammo, and that's about it.