One less publicized fact about the PNoy Administration’s acquisition of the Remington R4 Assault Rifles is how the Philippine Army (PA) and Philippine Marine Corps (PMC) can now also switch to using a newer type of ammo, the M855. This is because the R4 Rifles have barrels with 1 in 7 inch Twist Rates which allows them to do so.
First, just an explanation on the term “Twist Rate”: A bullet when it leaves the barrel of a firearm needs to be imparted a “spin” in order for it to travel further and on a more stable trajectory. Without this spin, then the bullet won’t be able to travel as accurately or as far and will drop to the ground quicker.
Grooves inside the barrel are “twisted” to guide a bullet into a spin. These twisted or spiral grooves are also known as “Rifling”. Now how much spin a bullet goes thru is expressed in terms of a “Twist Rate”, or how far the bullet travels before it completes one 360 degree revolution around its axis of travel.
So, if the Twist Rate is given as “1 in every 14 inches”, then that means one complete revolution is made by the bullet every time it travels 14 inches forward. In general, the heavier the bullet, the more twist at a shorter distance is needed to stabilize it and vice versa, the lighter the bullet, the less need to twist it for a given distance to stabilize it.
’The M193 and M855 Rounds’
The older M16A1 Rifles of the PA used mainly the M193 Ball ammunition, with the “Ball” term referring to a standard, solid military ammunition. The “M193” is its official designation in the United States (US) armed forces, and its official caliber is 5.56 x 45 mm, meaning the diameter of the bullet is 5.56 mm and the length of its Case is 45 mm. The M193 weighs 55 grains (around 3.6 g) and first entered service with the US Army way back in 1964.
The M855 Ball ammo on the other hand is a newer type of round introduced in 1980 as the standard 5.56 x 45 mm caliber round used by all forces of the North Atlantic Treaty Organization (NATO) with the official designation of “SS109” (the “M855” being the US armed forces’ designation). It was initially adopted by the Belgian Armed Forces in the early 1970s before it was adopted by NATO, and its construction of a Lead Core (or “Slug“) wrapped by a Copper Jacket is similar to that of the M193, except that it also has an added Solid Steel Tip (or the “Penetrator“).
This made the round longer by around 3.7 mm and heavier at 62 grains (or 4 g) than the M193, and is usually identified by having its tip painted Green, hence it is often also called as the “Green Tip” ammunition.
’Performance and Barrel Twist Effect’
The reason for putting a Steel tip on the M855 is to improve its performance in terms of Penetration at longer ranges compared to the M193. The M855, for example, is able to penetrate reliably a Steel Plate that is 3.5 mm thick and with an SAE Rating of 1010 or 1020 at 700 m when fired from an M16A2 Rifle. The Steel Plate approximates the Steel Helmets that were still common back in the 1970s and early 1980s. The M193 on the other hand can only penetrate the same Steel Plate reliably at 400 m. In terms of accuracy, both are roughly just about the same.
As a result though of being a heavier and longer bullet, the M855 needs to be fired from a barrel with more twist, at least a 1 in every 9 inch twist. Our new R4 Rifles have barrels with even more 1 in every 7 in twists, while the older M16A1s have lesser 1 in every 12 inch twist barrels. So what happens if you switch the ammo between the R4 and M16A1 rifles, then?
Well, if you use an M193 round on an R4 Rifle, the only issue there is that there will be a slight change in the Point of Impact, especially at longer ranges, hence some re-zeroing of the sights will be needed. But there are no other significant problems expected aside from that.
However, if you use an M855 round on an M16A1, there will be a major problem because the M16A1’s barrel won’t be able to stabilize well the heavier and longer bullet. In fact, using that combination of Rifle and Ammo is recommended only up to around 90 m, and that hitting a man-sized target beyond 100 m is already said to be difficult.
’More Comparisons with the M193’
Compared to the M193, there have been some reports, publications, websites, etc. over the years insisting that the M193 has better stopping power than the M855. However, a formal study made by the US Department of Defense (DoD) in 2008 on the issue shows that there is no difference in fragmentation and wound damage behavior even at close range between the two types of ammunition.
Overall the M855 is superior to the M193, especially in terms of defeating Barriers and still having enough power to damage an opponent behind it. A study by the US Army in 2006 showed how at 200 m, the M855 could still do Full Penetration on almost all 0.5 mm thick Aluminum Plates after passing thru Barriers like a Vehicle Windshield, a Truck Door or Concrete. The M193 on the other hand could only do Partial or No Penetration at all on similar Plates after going thru the same Barriers at that range.
’Stopping Power Controversy’
Another issue with the M855 is regarding its Stopping Power, and it is a very controversial topic. The US DoD does acknowledge the shortcoming of the M855 against Soft Tissue because it is a “Yaw-Dependent” round, just like the M193, meaning it needs to “Yaw” (i.e., tumble end over end) in order for it to expand and fragment and cause significant damage. The M855 also needs to do this as soon as it hits Soft Tissue or else it will just pass thru without yawing. How soon it yaws is determined by the “Yaw Angle” as it hits, and the higher it is, the better and vice versa, the lower it is, the worst.
Unfortunately, it is currently difficult (if not impossible) to control consistently at what Yaw Angle the bullet will hit a target as studies show that bullets from the same batch shot from different rifles can vary a lot in terms of Yaw. This phenomenon is what’s called as the “Fleet Yaw Issue”. And there are also other factors that affect Yaw Angle, like at what angle the bullet will hit the target, the shape of the target being hit, etc.
Note that the issue against the M855 is about “Stopping Power“, or the ability to immediately incapacitate a person, and not “Lethality“, the ability to cause death. NATO’s position in terms of Stopping Power is that it is best achieved using better Equipment, proper Shot Placement and realistic Training more than anything else, and that in terms of Lethality they consider the SS109/M855 to be equal to the bigger and more powerful 7.62 x 51 mm M80 Ball Ammo, and thus currently sufficient for their use.
Switching to the new M855 ammo by our armed forces won’t happen overnight, it will probably take a couple of years for it to be completed. After all, they still have to go thru all their existing inventory of M193 ammo.
But the Department of National Defense (DND) has already started some bidding for it, one of which was for the purchase of 10.5 million rounds, good enough to equip probably around 60% of our 70k troops (assuming each soldier gets 240 rounds for some Training and Combat Load). Our Government Arsenal (GA) has also been retooling their lines so they can produce the M855 locally, but they have been encountering some problems about doing so.
’Local Battlefield Impact’
As for what kind of impact it will have on the battlefield for our troops, I expect that it will have SOME impact, I am just not sure by how much. I expect our soldiers to be able to shoot at longer ranges with better results, and for the enemy to have less effective cover to hide behind, like Plywood, for example, or thick vegetation, or maybe the Thatched Walls of a Nipa Hut, etc.
Another impact I foresee is that it will force the rebels to upgrade at least the barrels of their weapons if they are using the 5.56 x 45 mm ammunition, assuming that the barrels of their weapons have more than 1 in every 9 inch twist. Once the switch to the M855 by our armed forces is complete, they just can’t pick up or steal ammunition anymore and use it on their weapons unless it has the required Twist Rate.
Note that our Armed Forces are not really strangers to the M855, the Daewoo K3 Squad Automatic Weapons (SAWs) that they have been using since 2008 are reportedly using it, and I have read some positive reports about their use here and there. Some of our Special Forces units with their HK416s and similar new, advanced rifles are also reportedly using it.
But the K3s were not issued in large numbers, only around 5,883 were purchased, and the Special Forces units with the newer rifles probably number only in the couple of thousands. Now when all of our frontline troops will be equipped with the M855 ammo thru their R4s, K3s, etc., then I expect it to have more impact.
The acquisition of the R4 not only allowed our Armed Forces to get new and better rifles, but newer and better ammunition as well. Of course the M855 is not really that “new”, it’s just that we are 35 years late in adopting it en masse for our troops. The M855 provides better performance against Barriers and longer effective ranges than the M193, and once the conversion to it is complete, then it will force our enemies to upgrade their rifles because a source of their ammo supply will be lessened, and probably also to keep up with the increased capability the M855 round.
While NATO is still using the M855, the US Armed Forces has since moved on to even better, more effective ammunition like the M855A1 for their Army, and the Mk 262 and the Mk 318 for their Special Forces. But I don’t see the Philippine Armed Forces following suit anytime soon, not unless NATO adopts them also. Even then, we might not switch as quickly because while these new types of ammo are more effective, they are also more expensive and require new investment in equipment if we are to produce them ourselves.
As for our troops, glad to see them now have access to better ammunition, I look forward to reading reports from them of its general performance in the years to come. Of course, assuming that we won’t switch to the Chinese QBZ-95 Assault Rifle and its 5.8 x 42 mm caliber round under Duterte, LOL. Just kidding …
^ How to Pair Barrel Twist Rates with Bullets,
^ M855: Facts, Falsehoods, and Fighting Back,
^ 5.56mm (.223) Paramilitary Ammunition,
^ The AR15.com Ammo-Oracle – Can I fire M193 ammo in my 1:7 or 1:9 twist barrel?
^ Army Study Guide – Ammunition Types and Characteristics,
^ Small Caliber Lethality: 5.56 mm Performance in Close Quarters Battle,
^ Effects of Small Caliber Munitions through Intermediate Barriers,
^ Weekly DTIC: The Fleet Yaw Problem, and Improving Rifle Effectiveness,
^ NATO Army Armaments Group – Is there a problem with the lethality of the 5.56 NATO caliber?
^ Supplemental Bulletin number DND/GA-M855-15-02 (Procurement of 5.56 mm M855 Bullet),
^ Is Army running out of ammo? – Miriam
^ Army Troopers Newsmagazine Volume 2 Number 9,