Let's design a new service rifle and cartridge...

[Failure2Stop]

A 6.5-7mm barrier blind projectile fired from a cartridge case with about 40 gr of capacity loaded with flash suppressed, heat stable powder optimized for full burn in a 16" barrel would be about perfect. Case head should be smaller diameter than current 7.62x51mm and case length should be a bit shorter--perhaps something around .440-460 base with a 46-47mm length; maybe using polymer case technology. Even better, something like a cased telescoping 7 mm could be used.

And that's pretty much the thread right there.
Sick it in an ACR type chassis and give it three to five years in the hands of real end-users for refinement.

Typos brought to you via Tapatalk and autocorrect.

[CRT2]

Some additional considerations - not inclusive:

Women assigned to Combat roles - weapon and round to fit them.

Role of the weapon/round - area fire, suppression, point targets and etc.

Are we designing for all terrain/climates?

Are we designing to stop wave attacks (Chinese in Korea) or something less?

Maximum effective range?

[Failure2Stop]

Women assigned to Combat roles - weapon and round to fit them.

I see this as a non-issue. It is the duty of the individual to meet the weight requirements of the service/specialty, not to lose equipment capability due to members that cannot perform the task.

Role of the weapon/round - area fire, suppression, point targets and etc.

The role of the individual weapon is to provide accurate fire on point targets, with secondary and tertiary requirements to provide fire on area targets at extended range and to supplement machinegun fire for suppression and area denial.

Are we designing for all terrain/climates?

Why would we not?

Are we designing to stop wave attacks (Chinese in Korea) or something less?

We constantly procure items based on the last war we fought. This cannot be the driving factor in the future or we will constantly be behind the curve. However, time and time again, it has been proven that the individual and unit training level is a greater impact on success than the tools used.

[/quote]
Maximum effective range?[/QUOTE]

The "not less than" would be the current 5.56 M855 or Mk262 Mod 1. The issue is what one uses as the criteria for "max effective".
Terminal effect versus precision capability are two very different aspects of performance.

[BrigandTwoFour]

I defer to Doc's experience on the cartridge matter. But, it looks like we're all pretty much in agreement of the bullet and case design. I really like the idea of the polymer cased ammo, which offers a lot of potential weight savings. LIke the telescoping ammo, though, has there been any issues with heat? I always thought part of the problem with caseless was that there was no ejecting brass to suck up chamber heat and carry it away from the weapon.

The issue is what one uses as the criteria for "max effective".
Terminal effect versus precision capability are two very different aspects of performance.

I think the max effective terminal effect should be around 500-600 meters, but with ammunition capable of precision reaching further if necessary. I don't think there is a need for every rifleman to reach 1000 yards (the thinking behind the 30-06), as it just doesn't appear to be a common engagement distance.

As far as fighting off "waves." I always thought that was the role of the light machine gun. But in this discussion, I think the modularity of the weapon is the key. If you need heavy automatic fire for the mission, then a heavy barreled upper and fixed stock sound appropriate. If you need light and fast, then shorter barreled upper and shorter stock.

Something I thought about last night when looking at pictures of the CZ, SCAR, and ACR is the forearm. I rather like the capability of the AR-15 to install a new forearm depending on how you want to use it (sticking support hand further out, mounting a bipod further out, recce configurations, etc).

IMO, the new rifle should have the same ability. But the forearm mounting system should be independent of the barrel nut. Perhaps an interface plate on the receiver.

[Koshinn]

IMO, the new rifle should have the same ability. But the forearm mounting system should be independent of the barrel nut. Perhaps an interface plate on the receiver.

Can't the ACR do that?

[BrigandTwoFour]

Can't the ACR do that?

Does it? I've never gotten to handle one. I think it makes sense to do it that way.

[Koshinn]

Does it? I've never gotten to handle one. I think it makes sense to do it that way.

http://www.northeastshooters.com/vbu...down-pics.html

Seems so. I don't have one. Doesn't seem like a stretch to create after-market compatible rails that extend further forward.

[BrigandTwoFour]

It seems that the ACR form factor is popular, with good reason. Have you seen much about the larger brother, the Massoud?

It would seem to be an ideal base platform for the cartridge we are talking about. It also uses a hybrid operating system that uses a gas tube over the barrel to impinge on a rear mounted piston, reducing the weight and reciprocating mass over the bore. An interesting concept, to say the least. Perhaps it uses the best of both worlds?

http://www.freepatentsonline.com/20100186582.pdf





Apparently the LR-20 PMAGS were designed to work with this system. What do you all think is an acceptable number of rounds carried in a standard magazine? I know we're all used to 30 rounds in the AR-15, but the original design had 20. With the larger cartridge we're discussing, how would that affect magazine capacity?

[MistWolf]

RIFLE
While designing a new rifle, there are features of the AR that should not be discarded.

All recoil forces and the reciprocating mass in the AR is inline with each other and the bore, greatly reducing muzzle displacement.

Some designs, such as the AK and the SCAR have long protuberances from their carriers which will flex and add to muzzle displacement. The AR does not.

The true receiver of the AR is the barrel extension which allows headspacing to be set as part of the manufacturing process, eliminating the need for it to be handfitted. The result is headspace is universal to all of the rifles, not unique to each individual unit.

There is evidence that the AR handles heat very well for it's mass. The AR dumps heat through more sources than most other rifles. What other rifle comes in at 7 lbs or so and can be run as hard before it fails?

The AR bolt is it's piston. The surface which the gases act on is larger than the piston of an op rod system, has greater mass and is subjected to far less heat. Because the operating gas is at a lower temperature, the piston can be oiled which reduces carbon build up.

The AR has good rigidity reducing flex and controls harmonics increasing shot to shot consistency.

AMMUNITION

First, let's look at what the 5.56 gives us- Lighter so the warfighter can carry more within the same weight limitations. Compact for space saving. Smaller case diameter to keep magazine length short. Less taper to reduce magazine curve.

Going with a larger diameter case results in needing a longer and possibly wider magazine to retain the same capacity. Increasing case taper means the mag must curve more to accommodate the taper. A curved magazine takes up more space than a straight mag and is more difficult to pull from a pouch. Case taper isn't needed for feeding. It helps with extraction when using steel cases. Tapered cases also do not grip the chamber walls as well which increases bolt thrust and the bolt and lock up will need to be beefed up accordingly.

Larger diameter projectiles and cases means a heavier ammo load and for what gain?

I am going to raise questions in an area I am not an expert in and indeed, do not know what I do not know- the finer details of terminal ballistics.

Why is the 9mm generally preferred over the 45? Because the difference in terminal performance is marginal, 9mm uses lighter, smaller ammo and recoil is reduced.

So what really is gained by switching from a .224" projectile to a .264 - .284"? Or even .308"? Using the case size under consideration, there will be a loss in velocity and an increase in recoil. The higher velocity of the 5.56 improves bullet fragmentation. Will going to a larger, heavier projectile, larger heavier case give enough increase in terminal performance to justify the penalty? Would it not be simpler to develop a 5.56 projectile that is more lethal and allow the US to assert it meets the requirements set down by the Hague, in order to retain the advantages the 5.56 offers?

IN CONCLUSION
As we design this hypothetical new weapon, we must figure out how it will exceed the performance of the current AR.

It must be no heavier. It must have equal or better recoil management. It must be as durable and reliable. It must have better terminal performance. It must be more effective on the battlefield. It must have a simple logistical train.

There are many modern weapons and calibers designed specifically to dethrone the AR and 5.56, yet none have been able to do so. Part of that is the fact the newcomers have been able to overcome institutional inertia and labyrinthine politics. But it's also due to the fact that both the AR and the 5.56 have been through the refiner's fire of hard combat and represent the best balance of features any modern combat rifles can offer. The biggest area of improvement lays with developing a better projectile and getting our government to allow a bit more leeway as to what they'll approve as being acceptable to the Hague

[SomeOtherGuy]

I'm not sure one cartridge for all situations makes any more sense than one camo for all terrain.

I think something like a .260 Rem or 6.5 Creedmoor (yes, nearly the same thing) would make lots of sense for infantry units in mountains or some desert situations, where a useful range of 1km+ is actually, uh, useful.

In other terrain (jungle, woodland, urban) and for non-infantry units, I would be thinking of something smaller and lighter. And the existing 5.56 NATO is probably adequate for those purposes. As would be 6.8 SPC, 300BLK, 7.62x39mm, etc.

If I had an unlimited budget for small arms for my private army, I would probably be looking at something like a SCAR-L in 6.8 SPC using the new (LWRC-related) Pmags for 6.8 SPC, as the general purpose and PDW weapon, with barrel lengths ranging from maybe 8-10" for vehicle crewmen to 14-16" or so for infantry type use.

In desert and mountains, I would be thinking along the lines of the SCAR-H or similar with that 6.5 CM type long distance cartridge.